12086 lines
233 KiB
Plaintext
12086 lines
233 KiB
Plaintext
#LyX 1.6.1 created this file. For more info see http://www.lyx.org/
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\lyxformat 345
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\begin_document
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\begin_header
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\author ""
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\author ""
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\end_header
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\begin_body
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\begin_layout Title
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The Speex Manual
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\begin_inset Newline newline
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Version 1.2
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\end_layout
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\begin_layout Author
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Jean-Marc Valin
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\begin_inset Newpage newpage
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Copyright
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\begin_layout Plain Layout
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\backslash
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copyright
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2002-2008 Jean-Marc Valin/Xiph.org Foundation
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\begin_layout Standard
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Permission is granted to copy, distribute and/or modify this document under
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the terms of the GNU Free Documentation License, Version 1.1 or any later
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version published by the Free Software Foundation; with no Invariant Section,
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with no Front-Cover Texts, and with no Back-Cover.
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A copy of the license is included in the section entitled "GNU Free Documentati
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on License".
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\end_layout
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\begin_layout Standard
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LatexCommand tableofcontents
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\begin_inset Newpage newpage
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\end_inset
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\end_layout
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\begin_layout Chapter
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Introduction to Speex
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\end_layout
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\begin_layout Standard
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The Speex codec (
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\family typewriter
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http://www.speex.org/
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\family default
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) exists because there is a need for a speech codec that is open-source
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and free from software patent royalties.
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These are essential conditions for being usable in any open-source software.
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In essence, Speex is to speech what Vorbis is to audio/music.
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Unlike many other speech codecs, Speex is not designed for mobile phones
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but rather for packet networks and voice over IP (VoIP) applications.
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File-based compression is of course also supported.
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\end_layout
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\begin_layout Standard
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The Speex codec is designed to be very flexible and support a wide range
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of speech quality and bit-rate.
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Support for very good quality speech also means that Speex can encode wideband
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speech (16 kHz sampling rate) in addition to narrowband speech (telephone
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quality, 8 kHz sampling rate).
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\end_layout
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\begin_layout Standard
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Designing for VoIP instead of mobile phones means that Speex is robust to
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lost packets, but not to corrupted ones.
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This is based on the assumption that in VoIP, packets either arrive unaltered
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or don't arrive at all.
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Because Speex is targeted at a wide range of devices, it has modest (adjustable
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) complexity and a small memory footprint.
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\end_layout
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\begin_layout Standard
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All the design goals led to the choice of CELP
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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CELP
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\end_layout
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\end_inset
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as the encoding technique.
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One of the main reasons is that CELP has long proved that it could work
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reliably and scale well to both low bit-rates (e.g.
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DoD CELP @ 4.8 kbps) and high bit-rates (e.g.
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G.728 @ 16 kbps).
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\end_layout
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\begin_layout Section
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Getting help
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\begin_inset CommandInset label
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LatexCommand label
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name "sec:Getting-help"
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\end_inset
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\end_layout
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\begin_layout Standard
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As for many open source projects, there are many ways to get help with Speex.
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These include:
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\end_layout
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\begin_layout Itemize
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This manual
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\end_layout
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\begin_layout Itemize
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Other documentation on the Speex website (http://www.speex.org/)
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\end_layout
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\begin_layout Itemize
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Mailing list: Discuss any Speex-related topic on speex-dev@xiph.org (not
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just for developers)
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\end_layout
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\begin_layout Itemize
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IRC: The main channel is #speex on irc.freenode.net.
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Note that due to time differences, it may take a while to get someone,
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so please be patient.
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\end_layout
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\begin_layout Itemize
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Email the author privately at jean-marc.valin@usherbrooke.ca
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\series bold
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only
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\series default
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for private/delicate topics you do not wish to discuss publicly.
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\end_layout
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\begin_layout Standard
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Before asking for help (mailing list or IRC),
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\series bold
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it is important to first read this manual
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\series default
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(OK, so if you made it here it's already a good sign).
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It is generally considered rude to ask on a mailing list about topics that
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are clearly detailed in the documentation.
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On the other hand, it's perfectly OK (and encouraged) to ask for clarifications
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about something covered in the manual.
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This manual does not (yet) cover everything about Speex, so everyone is
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encouraged to ask questions, send comments, feature requests, or just let
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us know how Speex is being used.
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\end_layout
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\begin_layout Standard
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Here are some additional guidelines related to the mailing list.
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Before reporting bugs in Speex to the list, it is strongly recommended
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(if possible) to first test whether these bugs can be reproduced using
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the speexenc and speexdec (see Section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:Command-line-encoder/decoder"
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\end_inset
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) command-line utilities.
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Bugs reported based on 3rd party code are both harder to find and far too
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often caused by errors that have nothing to do with Speex.
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\end_layout
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\begin_layout Section
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About this document
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\end_layout
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\begin_layout Standard
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This document is divided in the following way.
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Section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:Feature-description"
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\end_inset
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describes the different Speex features and defines many basic terms that
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are used throughout this manual.
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Section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:Command-line-encoder/decoder"
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\end_inset
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documents the standard command-line tools provided in the Speex distribution.
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Section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:Programming-with-Speex"
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\end_inset
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includes detailed instructions about programming using the libspeex
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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libspeex
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\end_layout
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\end_inset
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API.
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Section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:Formats-and-standards"
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\end_inset
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has some information related to Speex and standards.
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\end_layout
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\begin_layout Standard
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The three last sections describe the algorithms used in Speex.
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These sections require signal processing knowledge, but are not required
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for merely using Speex.
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They are intended for people who want to understand how Speex really works
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and/or want to do research based on Speex.
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Section
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:Introduction-to-CELP"
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\end_inset
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explains the general idea behind CELP, while sections
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:Speex-narrowband-mode"
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\end_inset
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and
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\begin_inset CommandInset ref
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LatexCommand ref
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reference "sec:Speex-wideband-mode"
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\end_inset
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are specific to Speex.
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\end_layout
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\begin_layout Standard
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\begin_inset Newpage newpage
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\end_inset
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\end_layout
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\begin_layout Chapter
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Codec description
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\begin_inset CommandInset label
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LatexCommand label
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name "sec:Feature-description"
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\end_inset
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\end_layout
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\begin_layout Standard
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This section describes Speex and its features into more details.
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\end_layout
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\begin_layout Section
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Concepts
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\end_layout
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\begin_layout Standard
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Before introducing all the Speex features, here are some concepts in speech
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coding that help better understand the rest of the manual.
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Although some are general concepts in speech/audio processing, others are
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specific to Speex.
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\end_layout
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\begin_layout Subsection*
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Sampling rate
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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sampling rate
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\end_layout
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\end_inset
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\end_layout
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\begin_layout Standard
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The sampling rate expressed in Hertz (Hz) is the number of samples taken
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from a signal per second.
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For a sampling rate of
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\begin_inset Formula $F_{s}$
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\end_inset
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kHz, the highest frequency that can be represented is equal to
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\begin_inset Formula $F_{s}/2$
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\end_inset
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kHz (
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\begin_inset Formula $F_{s}/2$
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\end_inset
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is known as the Nyquist frequency).
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This is a fundamental property in signal processing and is described by
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the sampling theorem.
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Speex is mainly designed for three different sampling rates: 8 kHz, 16
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kHz, and 32 kHz.
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These are respectively referred to as narrowband
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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narrowband
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\end_layout
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\end_inset
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, wideband
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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wideband
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\end_layout
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\end_inset
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and ultra-wideband
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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ultra-wideband
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\end_layout
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\end_inset
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.
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\end_layout
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\begin_layout Subsection*
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Bit-rate
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\end_layout
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\begin_layout Standard
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When encoding a speech signal, the bit-rate is defined as the number of
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bits per unit of time required to encode the speech.
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It is measured in
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\emph on
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bits per second
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\emph default
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(bps), or generally
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\emph on
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kilobits per second
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\emph default
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.
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It is important to make the distinction between
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\emph on
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kilo
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\series bold
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bits
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\series default
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\emph default
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\emph on
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per second
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\emph default
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(k
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\series bold
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b
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\series default
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ps) and
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\emph on
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kilo
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\series bold
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bytes
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\series default
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\emph default
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\emph on
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per second
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\emph default
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(k
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\series bold
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B
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\series default
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ps).
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\end_layout
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\begin_layout Subsection*
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Quality
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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quality
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\end_layout
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\end_inset
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(variable)
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\end_layout
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\begin_layout Standard
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Speex is a lossy codec, which means that it achieves compression at the
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expense of fidelity of the input speech signal.
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Unlike some other speech codecs, it is possible to control the trade-off
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made between quality and bit-rate.
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The Speex encoding process is controlled most of the time by a quality
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parameter that ranges from 0 to 10.
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In constant bit-rate
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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constant bit-rate
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\end_layout
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\end_inset
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(CBR) operation, the quality parameter is an integer, while for variable
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bit-rate (VBR), the parameter is a float.
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\end_layout
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\begin_layout Subsection*
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Complexity
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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complexity
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\end_layout
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\end_inset
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(variable)
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\end_layout
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\begin_layout Standard
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With Speex, it is possible to vary the complexity allowed for the encoder.
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This is done by controlling how the search is performed with an integer
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ranging from 1 to 10 in a way that's similar to the -1 to -9 options to
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\emph on
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gzip
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\emph default
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and
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\emph on
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bzip2
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\emph default
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compression utilities.
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For normal use, the noise level at complexity 1 is between 1 and 2 dB higher
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than at complexity 10, but the CPU requirements for complexity 10 is about
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5 times higher than for complexity 1.
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In practice, the best trade-off is between complexity 2 and 4, though higher
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settings are often useful when encoding non-speech sounds like DTMF
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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DTMF
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\end_layout
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\end_inset
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tones.
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\end_layout
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\begin_layout Subsection*
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Variable Bit-Rate
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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variable bit-rate
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\end_layout
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\end_inset
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(VBR)
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\end_layout
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\begin_layout Standard
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Variable bit-rate (VBR) allows a codec to change its bit-rate dynamically
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to adapt to the
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\begin_inset Quotes eld
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\end_inset
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difficulty
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\begin_inset Quotes erd
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\end_inset
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of the audio being encoded.
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In the example of Speex, sounds like vowels and high-energy transients
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require a higher bit-rate to achieve good quality, while fricatives (e.g.
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s,f sounds) can be coded adequately with less bits.
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For this reason, VBR can achieve lower bit-rate for the same quality, or
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a better quality for a certain bit-rate.
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Despite its advantages, VBR has two main drawbacks: first, by only specifying
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quality, there's no guaranty about the final average bit-rate.
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Second, for some real-time applications like voice over IP (VoIP), what
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counts is the maximum bit-rate, which must be low enough for the communication
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channel.
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\end_layout
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\begin_layout Subsection*
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Average Bit-Rate
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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average bit-rate
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\end_layout
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\end_inset
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(ABR)
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\end_layout
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\begin_layout Standard
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Average bit-rate solves one of the problems of VBR, as it dynamically adjusts
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VBR quality in order to meet a specific target bit-rate.
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Because the quality/bit-rate is adjusted in real-time (open-loop), the
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global quality will be slightly lower than that obtained by encoding in
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VBR with exactly the right quality setting to meet the target average bit-rate.
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\end_layout
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\begin_layout Subsection*
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Voice Activity Detection
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\begin_inset Index
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status collapsed
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\begin_layout Plain Layout
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voice activity detection
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\end_layout
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\end_inset
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(VAD)
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\end_layout
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\begin_layout Standard
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When enabled, voice activity detection detects whether the audio being encoded
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is speech or silence/background noise.
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VAD is always implicitly activated when encoding in VBR, so the option
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is only useful in non-VBR operation.
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In this case, Speex detects non-speech periods and encode them with just
|
|
enough bits to reproduce the background noise.
|
|
This is called
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
comfort noise generation
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
(CNG).
|
|
\end_layout
|
|
|
|
\begin_layout Subsection*
|
|
Discontinuous Transmission
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
discontinuous transmission
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(DTX)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Discontinuous transmission is an addition to VAD/VBR operation, that allows
|
|
to stop transmitting completely when the background noise is stationary.
|
|
In file-based operation, since we cannot just stop writing to the file,
|
|
only 5 bits are used for such frames (corresponding to 250 bps).
|
|
\end_layout
|
|
|
|
\begin_layout Subsection*
|
|
Perceptual enhancement
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
perceptual enhancement
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Perceptual enhancement is a part of the decoder which, when turned on, attempts
|
|
to reduce the perception of the noise/distortion produced by the encoding/decod
|
|
ing process.
|
|
In most cases, perceptual enhancement brings the sound further from the
|
|
original
|
|
\emph on
|
|
objectively
|
|
\emph default
|
|
(e.g.
|
|
considering only SNR), but in the end it still
|
|
\emph on
|
|
sounds
|
|
\emph default
|
|
better (subjective improvement).
|
|
\end_layout
|
|
|
|
\begin_layout Subsection*
|
|
Latency and algorithmic delay
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
algorithmic delay
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Every speech codec introduces a delay in the transmission.
|
|
For Speex, this delay is equal to the frame size, plus some amount of
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
look-ahead
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
required to process each frame.
|
|
In narrowband operation (8 kHz), the look-ahead is 10 ms, in wideband operation
|
|
(16 kHz), the look-ahead is 13.9 ms and in ultra-wideband operation (32
|
|
kHz) look-ahead is 15.9 ms, resulting in the algorithic delays of 30 ms,
|
|
33.9 ms and 35.9 ms accordingly.
|
|
These values don't account for the CPU time it takes to encode or decode
|
|
the frames.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Codec
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The main characteristics of Speex can be summarized as follows:
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Free software/open-source
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
open-source
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, patent
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
patent
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
and royalty-free
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Integration of narrowband
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
narrowband
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
and wideband
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
wideband
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
using an embedded bit-stream
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Wide range of bit-rates available (from 2.15 kbps to 44 kbps)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Dynamic bit-rate switching (AMR) and Variable Bit-Rate
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
variable bit-rate
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(VBR) operation
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Voice Activity Detection
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
voice activity detection
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(VAD, integrated with VBR) and discontinuous transmission (DTX)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Variable complexity
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
complexity
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Embedded wideband structure (scalable sampling rate)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Ultra-wideband sampling rate at 32 kHz
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Intensity stereo encoding option
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Fixed-point implementation
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Preprocessor
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This part refers to the preprocessor module introduced in the 1.1.x branch.
|
|
The preprocessor is designed to be used on the audio
|
|
\emph on
|
|
before
|
|
\emph default
|
|
running the encoder.
|
|
The preprocessor provides three main functionalities:
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
noise suppression
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
automatic gain control (AGC)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
voice activity detection (VAD)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The denoiser can be used to reduce the amount of background noise present
|
|
in the input signal.
|
|
This provides higher quality speech whether or not the denoised signal
|
|
is encoded with Speex (or at all).
|
|
However, when using the denoised signal with the codec, there is an additional
|
|
benefit.
|
|
Speech codecs in general (Speex included) tend to perform poorly on noisy
|
|
input, which tends to amplify the noise.
|
|
The denoiser greatly reduces this effect.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Automatic gain control (AGC) is a feature that deals with the fact that
|
|
the recording volume may vary by a large amount between different setups.
|
|
The AGC provides a way to adjust a signal to a reference volume.
|
|
This is useful for voice over IP because it removes the need for manual
|
|
adjustment of the microphone gain.
|
|
A secondary advantage is that by setting the microphone gain to a conservative
|
|
(low) level, it is easier to avoid clipping.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The voice activity detector (VAD) provided by the preprocessor is more advanced
|
|
than the one directly provided in the codec.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Adaptive Jitter Buffer
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
When transmitting voice (or any content for that matter) over UDP or RTP,
|
|
packet may be lost, arrive with different delay, or even out of order.
|
|
The purpose of a jitter buffer is to reorder packets and buffer them long
|
|
enough (but no longer than necessary) so they can be sent to be decoded.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Acoustic Echo Canceller
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In any hands-free communication system (Fig.
|
|
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:Acoustic-echo-model"
|
|
|
|
\end_inset
|
|
|
|
), speech from the remote end is played in the local loudspeaker, propagates
|
|
in the room and is captured by the microphone.
|
|
If the audio captured from the microphone is sent directly to the remote
|
|
end, then the remote user hears an echo of his voice.
|
|
An acoustic echo canceller is designed to remove the acoustic echo before
|
|
it is sent to the remote end.
|
|
It is important to understand that the echo canceller is meant to improve
|
|
the quality on the
|
|
\series bold
|
|
remote
|
|
\series default
|
|
end.
|
|
For those who care a lot about mouth-to-ear delays it should be noted that
|
|
unlike Speex codec, resampler and preprocessor, this Acoustic Echo Canceller
|
|
does not introduce any latency.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Graphics
|
|
filename echo_path.eps
|
|
width 10cm
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
end{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
Acoustic echo model
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:Acoustic-echo-model"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Resampler
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In some cases, it may be useful to convert audio from one sampling rate
|
|
to another.
|
|
There are many reasons for that.
|
|
It can be for mixing streams that have different sampling rates, for supporting
|
|
sampling rates that the soundcard doesn't support, for transcoding, etc.
|
|
That's why there is now a resampler that is part of the Speex project.
|
|
This resampler can be used to convert between any two arbitrary rates (the
|
|
ratio must only be a rational number) and there is control over the quality/com
|
|
plexity tradeoff.
|
|
Keep in mind, that resampler introduce some delay in audio stream, which
|
|
size depends on resampler quality setting.
|
|
Refer to resampler API documentation to know how to get exact delay values.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Integration
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Knowing
|
|
\emph on
|
|
how
|
|
\emph default
|
|
to use each of the components is not that useful unless we know
|
|
\emph on
|
|
where
|
|
\emph default
|
|
to use them.
|
|
Figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:Integration-VoIP"
|
|
|
|
\end_inset
|
|
|
|
shows where each of the components would be used in a typical VoIP client.
|
|
Components in dotted lines are optional, though they may be very useful
|
|
in some circumstances.
|
|
There are several important things to note from there.
|
|
The AEC must be placed as close as possible to the playback and capture.
|
|
Only the resampling may be closer.
|
|
Also, it is very important to use the same clock for both mic capture and
|
|
speaker/headphones playback.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Graphics
|
|
filename components.eps
|
|
width 80text%
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
end{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
Integration of all the components in a VoIP client.
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:Integration-VoIP"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
Compiling and Porting
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Compiling Speex under UNIX/Linux or any other platform supported by autoconf
|
|
(e.g.
|
|
Win32/cygwin) is as easy as typing:
|
|
\end_layout
|
|
|
|
\begin_layout LyX-Code
|
|
% ./configure [options]
|
|
\end_layout
|
|
|
|
\begin_layout LyX-Code
|
|
% make
|
|
\end_layout
|
|
|
|
\begin_layout LyX-Code
|
|
% make install
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The options supported by the Speex configure script are:
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--prefix=<path> Specifies the base path for installing Speex (e.g.
|
|
/usr)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enable-shared/--disable-shared Whether to compile shared libraries
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enable-static/--disable-static Whether to compile static libraries
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--disable-wideband Disable the wideband part of Speex (typically to save
|
|
space)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enable-valgrind Enable extra hits for valgrind for debugging purposes
|
|
(do not use by default)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enable-sse Enable use of SSE instructions (x86/float only)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enable-fixed-point
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
fixed-point
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
Compile Speex for a processor that does not have a floating point unit
|
|
(FPU)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enable-arm4-asm Enable assembly specific to the ARMv4 architecture (gcc
|
|
only)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enable-arm5e-asm Enable assembly specific to the ARMv5E architecture (gcc
|
|
only)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enable-fixed-point-debug Use only for debugging the fixed-point
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
fixed-point
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
code (very slow)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enable-ti-c55x Enable support for the TI C5x family
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enable-blackfin-asm Enable assembly specific to the Blackfin DSP architecture
|
|
(gcc only)
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Platforms
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Speex is known to compile and work on a large number of architectures, both
|
|
floating-point and fixed-point.
|
|
In general, any architecture that can natively compute the multiplication
|
|
of two signed 16-bit numbers (32-bit result) and runs at a sufficient clock
|
|
rate (architecture-dependent) is capable of running Speex.
|
|
Architectures on which Speex is
|
|
\series bold
|
|
known
|
|
\series default
|
|
to work (it probably works on many others) are:
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
x86 & x86-64
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Power
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
SPARC
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
ARM
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Blackfin
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Coldfire (68k family)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
TI C54xx & C55xx
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
TI C6xxx
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
TriMedia (experimental)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Operating systems on top of which Speex is known to work include (it probably
|
|
works on many others):
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Linux
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
\begin_inset Formula $\mu$
|
|
\end_inset
|
|
|
|
Clinux
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
MacOS X
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
BSD
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Other UNIX/POSIX variants
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Symbian
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The source code directory include additional information for compiling on
|
|
certain architectures or operating systems in README.xxx files.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Porting and Optimising
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Here are a few things to consider when porting or optimising Speex for a
|
|
new platform or an existing one.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
CPU optimisation
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The single factor that will affect the CPU usage of Speex the most is whether
|
|
it is compiled for floating point or fixed-point.
|
|
If your CPU/DSP does not have a floating-point unit FPU, then compiling
|
|
as fixed-point will be orders of magnitudes faster.
|
|
If there is an FPU present, then it is important to test which version
|
|
is faster.
|
|
On the x86 architecture, floating-point is
|
|
\series bold
|
|
generally
|
|
\series default
|
|
faster, but not always.
|
|
To compile Speex as fixed-point, you need to pass --fixed-point to the
|
|
configure script or define the FIXED_POINT macro for the compiler.
|
|
As of 1.2beta3, it is now possible to disable the floating-point compatibility
|
|
API, which means that your code can link without a float emulation library.
|
|
To do that configure with --disable-float-api or define the DISABLE_FLOAT_API
|
|
macro.
|
|
Until the VBR feature is ported to fixed-point, you will also need to configure
|
|
with --disable-vbr or define DISABLE_VBR.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Other important things to check on some DSP architectures are:
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Make sure the cache is set to write-back mode
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
If the chip has SRAM instead of cache, make sure as much code and data are
|
|
in SRAM, rather than in RAM
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
If you are going to be writing assembly, then the following functions are
|
|
|
|
\series bold
|
|
usually
|
|
\series default
|
|
the first ones you should consider optimising:
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
filter_mem16()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
iir_mem16()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
vq_nbest()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
pitch_xcorr()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
interp_pitch()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The filtering functions
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
filter_mem16()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
and
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
iir_mem16()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
are implemented in the direct form II transposed (DF2T).
|
|
However, for architectures based on multiply-accumulate (MAC), DF2T requires
|
|
frequent reload of the accumulator, which can make the code very slow.
|
|
For these architectures (e.g.
|
|
Blackfin and Coldfire), a better approach is to implement those functions
|
|
as direct form I (DF1), which is easier to express in terms of MAC.
|
|
When doing that however,
|
|
\series bold
|
|
it is important to make sure that the DF1 implementation still behaves like
|
|
the original DF2T behaviour when it comes to memory values
|
|
\series default
|
|
.
|
|
This is necessary because the filter is time-varying and must compute exactly
|
|
the same value (not counting machine rounding) on any encoder or decoder.
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Memory optimisation
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Memory optimisation is mainly something that should be considered for small
|
|
embedded platforms.
|
|
For PCs, Speex is already so tiny that it's just not worth doing any of
|
|
the things suggested here.
|
|
There are several ways to reduce the memory usage of Speex, both in terms
|
|
of code size and data size.
|
|
For optimising code size, the trick is to first remove features you do
|
|
not need.
|
|
Some examples of things that can easily be disabled
|
|
\series bold
|
|
if you don't need them
|
|
\series default
|
|
are:
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Wideband support (--disable-wideband)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Support for stereo (removing stereo.c)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
VBR support (--disable-vbr or DISABLE_VBR)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Static codebooks that are not needed for the bit-rates you are using (*_table.c
|
|
files)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Speex also has several methods for allocating temporary arrays.
|
|
When using a compiler that supports C99 properly (as of 2007, Microsoft
|
|
compilers don't, but gcc does), it is best to define VAR_ARRAYS.
|
|
That makes use of the variable-size array feature of C99.
|
|
The next best is to define USE_ALLOCA so that Speex can use alloca() to
|
|
allocate the temporary arrays.
|
|
Note that on many systems, alloca() is buggy so it may not work.
|
|
If none of VAR_ARRAYS and USE_ALLOCA are defined, then Speex falls back
|
|
to allocating a large
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
scratch space
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
and doing its own internal allocation.
|
|
The main disadvantage of this solution is that it is wasteful.
|
|
It needs to allocate enough stack for the worst case scenario (worst bit-rate,
|
|
highest complexity setting, ...) and by default, the memory isn't shared between
|
|
multiple encoder/decoder states.
|
|
Still, if the
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
manual
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
allocation is the only option left, there are a few things that can be
|
|
improved.
|
|
By overriding the speex_alloc_scratch() call in os_support.h, it is possible
|
|
to always return the same memory area for all states
|
|
\begin_inset Foot
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
In this case, one must be careful with threads
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
In addition to that, by redefining the NB_ENC_STACK and NB_DEC_STACK (or
|
|
similar for wideband), it is possible to only allocate memory for a scenario
|
|
that is known in advance.
|
|
In this case, it is important to measure the amount of memory required
|
|
for the specific sampling rate, bit-rate and complexity level being used.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
Command-line encoder/decoder
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:Command-line-encoder/decoder"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The base Speex distribution includes a command-line encoder (
|
|
\emph on
|
|
speexenc
|
|
\emph default
|
|
) and decoder (
|
|
\emph on
|
|
speexdec
|
|
\emph default
|
|
).
|
|
Those tools produce and read Speex files encapsulated in the Ogg container.
|
|
Although it is possible to encapsulate Speex in any container, Ogg is the
|
|
recommended container for files.
|
|
This section describes how to use the command line tools for Speex files
|
|
in Ogg.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
|
|
\emph on
|
|
speexenc
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
speexenc
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The
|
|
\emph on
|
|
speexenc
|
|
\emph default
|
|
utility is used to create Speex files from raw PCM or wave files.
|
|
It can be used by calling:
|
|
\end_layout
|
|
|
|
\begin_layout LyX-Code
|
|
speexenc [options] input_file output_file
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The value '-' for input_file or output_file corresponds respectively to
|
|
stdin and stdout.
|
|
The valid options are:
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--narrowband
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
(-n) Tell Speex to treat the input as narrowband (8 kHz).
|
|
This is the default
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--wideband
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
(-w) Tell Speex to treat the input as wideband (16 kHz)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--ultra-wideband
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
(-u) Tell Speex to treat the input as
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
ultra-wideband
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
(32 kHz)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--quality
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
n Set the encoding quality (0-10), default is 8
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--bitrate
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
n Encoding bit-rate (use bit-rate n or lower)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--vbr Enable VBR (Variable Bit-Rate), disabled by default
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--abr
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
n Enable ABR (Average Bit-Rate) at n kbps, disabled by default
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--vad Enable VAD (Voice Activity Detection), disabled by default
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--dtx Enable DTX (Discontinuous Transmission), disabled by default
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--nframes
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
n Pack n frames in each Ogg packet (this saves space at low bit-rates)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--comp
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
n Set encoding speed/quality tradeoff.
|
|
The higher the value of n, the slower the encoding (default is 3)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
-V Verbose operation, print bit-rate currently in use
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--help
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
(-h) Print the help
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--version
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
(-v) Print version information
|
|
\end_layout
|
|
|
|
\begin_layout Subsection*
|
|
Speex comments
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--comment Add the given string as an extra comment.
|
|
This may be used multiple times.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--author Author of this track.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--title Title for this track.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsection*
|
|
Raw input options
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--rate
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
n Sampling rate for raw input
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--stereo Consider raw input as stereo
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--le Raw input is little-endian
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--be Raw input is big-endian
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--8bit Raw input is 8-bit unsigned
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--16bit Raw input is 16-bit signed
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
|
|
\emph on
|
|
speexdec
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
speexdec
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The
|
|
\emph on
|
|
speexdec
|
|
\emph default
|
|
utility is used to decode Speex files and can be used by calling:
|
|
\end_layout
|
|
|
|
\begin_layout LyX-Code
|
|
speexdec [options] speex_file [output_file]
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The value '-' for input_file or output_file corresponds respectively to
|
|
stdin and stdout.
|
|
Also, when no output_file is specified, the file is played to the soundcard.
|
|
The valid options are:
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--enh enable post-filter (default)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--no-enh disable post-filter
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--force-nb Force decoding in narrowband
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--force-wb Force decoding in wideband
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--force-uwb Force decoding in ultra-wideband
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--mono Force decoding in mono
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--stereo Force decoding in stereo
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--rate
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
n Force decoding at n Hz sampling rate
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--packet-loss
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
n Simulate n % random packet loss
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
-V Verbose operation, print bit-rate currently in use
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--help
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
(-h) Print the help
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
--version
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
(-v) Print version information
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
Using the Speex Codec API (
|
|
\emph on
|
|
libspeex
|
|
\emph default
|
|
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
libspeex
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:Programming-with-Speex"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The
|
|
\emph on
|
|
libspeex
|
|
\emph default
|
|
library contains all the functions for encoding and decoding speech with
|
|
the Speex codec.
|
|
When linking on a UNIX system, one must add
|
|
\emph on
|
|
-lspeex -lm
|
|
\emph default
|
|
to the compiler command line.
|
|
One important thing to know is that
|
|
\series bold
|
|
libspeex calls are reentrant, but not thread-safe
|
|
\series default
|
|
.
|
|
That means that it is fine to use calls from many threads, but
|
|
\series bold
|
|
calls using the same state from multiple threads must be protected by mutexes
|
|
\series default
|
|
.
|
|
Examples of code can also be found in Appendix
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "sec:Sample-code"
|
|
|
|
\end_inset
|
|
|
|
and the complete API documentation is included in the Documentation section
|
|
of the Speex website (http://www.speex.org/).
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Encoding
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sub:Encoding"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In order to encode speech using Speex, one first needs to:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
#include <speex/speex.h>
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
Then in the code, a Speex bit-packing struct must be declared, along with
|
|
a Speex encoder state:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
SpeexBits bits;
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
void *enc_state;
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
The two are initialized by:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_bits_init(&bits);
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
enc_state = speex_encoder_init(&speex_nb_mode);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For wideband coding,
|
|
\emph on
|
|
speex_nb_mode
|
|
\emph default
|
|
will be replaced by
|
|
\emph on
|
|
speex_wb_mode
|
|
\emph default
|
|
.
|
|
In most cases, you will need to know the frame size used at the sampling
|
|
rate you are using.
|
|
You can get that value in the
|
|
\emph on
|
|
frame_size
|
|
\emph default
|
|
variable (expressed in
|
|
\series bold
|
|
samples
|
|
\series default
|
|
, not bytes) with:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_encoder_ctl(enc_state,SPEEX_GET_FRAME_SIZE,&frame_size);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In practice,
|
|
\emph on
|
|
frame_size
|
|
\emph default
|
|
will correspond to 20 ms when using 8, 16, or 32 kHz sampling rate.
|
|
There are many parameters that can be set for the Speex encoder, but the
|
|
most useful one is the quality parameter that controls the quality vs bit-rate
|
|
tradeoff.
|
|
This is set by:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_encoder_ctl(enc_state,SPEEX_SET_QUALITY,&quality);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
where
|
|
\emph on
|
|
quality
|
|
\emph default
|
|
is an integer value ranging from 0 to 10 (inclusively).
|
|
The mapping between quality and bit-rate is described in Fig.
|
|
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:quality_vs_bps"
|
|
|
|
\end_inset
|
|
|
|
for narrowband.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Once the initialization is done, for every input frame:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_bits_reset(&bits);
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_encode_int(enc_state, input_frame, &bits);
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
nbBytes = speex_bits_write(&bits, byte_ptr, MAX_NB_BYTES);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
where
|
|
\emph on
|
|
input_frame
|
|
\emph default
|
|
is a
|
|
\emph on
|
|
(
|
|
\emph default
|
|
short
|
|
\emph on
|
|
*)
|
|
\emph default
|
|
pointing to the beginning of a speech frame,
|
|
\emph on
|
|
byte_ptr
|
|
\emph default
|
|
is a
|
|
\emph on
|
|
(char *)
|
|
\emph default
|
|
where the encoded frame will be written,
|
|
\emph on
|
|
MAX_NB_BYTES
|
|
\emph default
|
|
is the maximum number of bytes that can be written to
|
|
\emph on
|
|
byte_ptr
|
|
\emph default
|
|
without causing an overflow and
|
|
\emph on
|
|
nbBytes
|
|
\emph default
|
|
is the number of bytes actually written to
|
|
\emph on
|
|
byte_ptr
|
|
\emph default
|
|
(the encoded size in bytes).
|
|
Before calling speex_bits_write, it is possible to find the number of bytes
|
|
that need to be written by calling
|
|
\family typewriter
|
|
speex_bits_nbytes(&bits)
|
|
\family default
|
|
, which returns a number of bytes.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
It is still possible to use the
|
|
\emph on
|
|
speex_encode()
|
|
\emph default
|
|
function, which takes a
|
|
\emph on
|
|
(float *)
|
|
\emph default
|
|
for the audio.
|
|
However, this would make an eventual port to an FPU-less platform (like
|
|
ARM) more complicated.
|
|
Internally,
|
|
\emph on
|
|
speex_encode()
|
|
\emph default
|
|
and
|
|
\emph on
|
|
speex_encode_int()
|
|
\emph default
|
|
are processed in the same way.
|
|
Whether the encoder uses the fixed-point version is only decided by the
|
|
compile-time flags, not at the API level.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
After you're done with the encoding, free all resources with:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_bits_destroy(&bits);
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_encoder_destroy(enc_state);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
That's about it for the encoder.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Decoding
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sub:Decoding"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In order to decode speech using Speex, you first need to:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
#include <speex/speex.h>
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
You also need to declare a Speex bit-packing struct
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
SpeexBits bits;
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
and a Speex decoder state
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
void *dec_state;
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
The two are initialized by:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_bits_init(&bits);
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
dec_state = speex_decoder_init(&speex_nb_mode);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For wideband decoding,
|
|
\emph on
|
|
speex_nb_mode
|
|
\emph default
|
|
will be replaced by
|
|
\emph on
|
|
speex_wb_mode
|
|
\emph default
|
|
.
|
|
If you need to obtain the size of the frames that will be used by the decoder,
|
|
you can get that value in the
|
|
\emph on
|
|
frame_size
|
|
\emph default
|
|
variable (expressed in
|
|
\series bold
|
|
samples
|
|
\series default
|
|
, not bytes) with:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_decoder_ctl(dec_state, SPEEX_GET_FRAME_SIZE, &frame_size);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
There is also a parameter that can be set for the decoder: whether or not
|
|
to use a perceptual enhancer.
|
|
This can be set by:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_decoder_ctl(dec_state, SPEEX_SET_ENH, &enh);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
where
|
|
\emph on
|
|
enh
|
|
\emph default
|
|
is an int with value 0 to have the enhancer disabled and 1 to have it enabled.
|
|
As of 1.2-beta1, the default is now to enable the enhancer.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Again, once the decoder initialization is done, for every input frame:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_bits_read_from(&bits, input_bytes, nbBytes);
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_decode_int(dec_state, &bits, output_frame);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
where input_bytes is a
|
|
\emph on
|
|
(char *)
|
|
\emph default
|
|
containing the bit-stream data received for a frame,
|
|
\emph on
|
|
nbBytes
|
|
\emph default
|
|
is the size (in bytes) of that bit-stream, and
|
|
\emph on
|
|
output_frame
|
|
\emph default
|
|
is a
|
|
\emph on
|
|
(short *)
|
|
\emph default
|
|
and points to the area where the decoded speech frame will be written.
|
|
A NULL value as the second argument indicates that we don't have the bits
|
|
for the current frame.
|
|
When a frame is lost, the Speex decoder will do its best to "guess" the
|
|
correct signal.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As for the encoder, the
|
|
\emph on
|
|
speex_decode()
|
|
\emph default
|
|
function can still be used, with a
|
|
\emph on
|
|
(float *)
|
|
\emph default
|
|
as the output for the audio.
|
|
After you're done with the decoding, free all resources with:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_bits_destroy(&bits);
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_decoder_destroy(dec_state);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Codec Options (speex_*_ctl)
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sub:Codec-Options"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Quote
|
|
\align center
|
|
|
|
\emph on
|
|
Entities should not be multiplied beyond necessity -- William of Ockham.
|
|
\end_layout
|
|
|
|
\begin_layout Quote
|
|
\align center
|
|
|
|
\emph on
|
|
Just because there's an option for it doesn't mean you have to turn it on
|
|
-- me.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The Speex encoder and decoder support many options and requests that can
|
|
be accessed through the
|
|
\emph on
|
|
speex_encoder_ctl
|
|
\emph default
|
|
and
|
|
\emph on
|
|
speex_decoder_ctl
|
|
\emph default
|
|
functions.
|
|
These functions are similar to the
|
|
\emph on
|
|
ioctl
|
|
\emph default
|
|
system call and their prototypes are:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
void speex_encoder_ctl(void *encoder, int request, void *ptr);
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
void speex_decoder_ctl(void *encoder, int request, void *ptr);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Despite those functions, the defaults are usually good for many applications
|
|
and
|
|
\series bold
|
|
optional settings should only be used when one understands them and knows
|
|
that they are needed
|
|
\series default
|
|
.
|
|
A common error is to attempt to set many unnecessary settings.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Here is a list of the values allowed for the requests.
|
|
Some only apply to the encoder or the decoder.
|
|
Because the last argument is of type
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
void *
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, the
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
_ctl()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
functions are
|
|
\series bold
|
|
not type safe
|
|
\series default
|
|
, and should thus be used with care.
|
|
The type
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
is the same as the C99
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
type.
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_ENH
|
|
\begin_inset Formula $\ddagger$
|
|
\end_inset
|
|
|
|
Set perceptual enhancer
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
perceptual enhancement
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
to on (1) or off (0) (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, default is on)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_ENH
|
|
\begin_inset Formula $\ddagger$
|
|
\end_inset
|
|
|
|
Get perceptual enhancer status (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_FRAME_SIZE Get the number of samples per frame for the current
|
|
mode (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_QUALITY
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Set the encoder speech quality (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
from 0 to 10, default is 8)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_QUALITY
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Get the current encoder speech quality (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
from 0 to 10)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_MODE
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Set the mode number, as specified in the RTP spec (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_MODE
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Get the current mode number, as specified in the RTP spec (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_VBR
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Set variable bit-rate (VBR) to on (1) or off (0) (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, default is off)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_VBR
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Get variable bit-rate
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
variable bit-rate
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(VBR) status (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_VBR_QUALITY
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Set the encoder VBR speech quality (float 0.0 to 10.0, default is 8.0)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_VBR_QUALITY
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Get the current encoder VBR speech quality (float 0 to 10)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_COMPLEXITY
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Set the CPU resources allowed for the encoder (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
from 1 to 10, default is 2)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_COMPLEXITY
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Get the CPU resources allowed for the encoder (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
from 1 to 10, default is 2)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_BITRATE
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Set the bit-rate to use the closest value not exceeding the parameter (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in bits per second)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_BITRATE Get the current bit-rate in use (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in bits per second)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_SAMPLING_RATE Set real sampling rate (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in Hz)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_SAMPLING_RATE Get real sampling rate (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in Hz)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_RESET_STATE Reset the encoder/decoder state to its original state,
|
|
clearing all memories (no argument)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_VAD
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Set voice activity detection
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
voice activity detection
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(VAD) to on (1) or off (0) (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, default is off)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_VAD
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Get voice activity detection (VAD) status (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_DTX
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Set discontinuous transmission
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
discontinuous transmission
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(DTX) to on (1) or off (0) (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, default is off)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_DTX
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Get discontinuous transmission (DTX) status (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_ABR
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Set average bit-rate
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
average bit-rate
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(ABR) to a value n in bits per second (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in bits per second)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_ABR
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Get average bit-rate (ABR) setting (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in bits per second)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_PLC_TUNING
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Tell the encoder to optimize encoding for a certain percentage of packet
|
|
loss (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in percent)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_PLC_TUNING
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Get the current tuning of the encoder for PLC (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in percent)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_LOOKAHEAD Returns the lookahead used by Speex separately for an
|
|
encoder and a decoder.
|
|
Sum encoder and decoder lookahead values to get the total codec lookahead.
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_VBR_MAX_BITRATE
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Set the maximum bit-rate allowed in VBR operation (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in bits per second)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_VBR_MAX_BITRATE
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
Get the current maximum bit-rate allowed in VBR operation (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in bits per second)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SET_HIGHPASS Set the high-pass filter on (1) or off (0) (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, default is on)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_GET_HIGHPASS Get the current high-pass filter status (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
\begin_inset Formula $\dagger$
|
|
\end_inset
|
|
|
|
applies only to the encoder
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
\begin_inset Formula $\ddagger$
|
|
\end_inset
|
|
|
|
applies only to the decoder
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Mode queries
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sub:Mode-queries"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Speex modes have a query system similar to the speex_encoder_ctl and speex_decod
|
|
er_ctl calls.
|
|
Since modes are read-only, it is only possible to get information about
|
|
a particular mode.
|
|
The function used to do that is:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
void speex_mode_query(SpeexMode *mode, int request, void *ptr);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
The admissible values for request are (unless otherwise note, the values
|
|
are returned through
|
|
\emph on
|
|
ptr
|
|
\emph default
|
|
):
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_MODE_FRAME_SIZE Get the frame size (in samples) for the mode
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_SUBMODE_BITRATE Get the bit-rate for a submode number specified through
|
|
|
|
\emph on
|
|
ptr
|
|
\emph default
|
|
(integer in bps).
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Packing and in-band signalling
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
in-band signalling
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Sometimes it is desirable to pack more than one frame per packet (or other
|
|
basic unit of storage).
|
|
The proper way to do it is to call speex_encode
|
|
\begin_inset Formula $N$
|
|
\end_inset
|
|
|
|
times before writing the stream with speex_bits_write.
|
|
In cases where the number of frames is not determined by an out-of-band
|
|
mechanism, it is possible to include a terminator code.
|
|
That terminator consists of the code 15 (decimal) encoded with 5 bits,
|
|
as shown in Table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:quality_vs_bps"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
Note that as of version 1.0.2, calling speex_bits_write automatically inserts
|
|
the terminator so as to fill the last byte.
|
|
This doesn't involves any overhead and makes sure Speex can always detect
|
|
when there is no more frame in a packet.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
It is also possible to send in-band
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
messages
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
to the other side.
|
|
All these messages are encoded as
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
pseudo-frames
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
of mode 14 which contain a 4-bit message type code, followed by the message.
|
|
Table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:In-band-signalling-codes"
|
|
|
|
\end_inset
|
|
|
|
lists the available codes, their meaning and the size of the message that
|
|
follows.
|
|
Most of these messages are requests that are sent to the encoder or decoder
|
|
on the other end, which is free to comply or ignore them.
|
|
By default, all in-band messages are ignored.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float table
|
|
placement htbp
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="17" columns="3">
|
|
<features>
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Code
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Size (bits)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Content
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Asks decoder to set perceptual enhancement off (0) or on(1)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Asks (if 1) the encoder to be less
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
aggressive
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
due to high packet loss
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
2
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Asks encoder to switch to mode N
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Asks encoder to switch to mode N for low-band
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Asks encoder to switch to mode N for high-band
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Asks encoder to switch to quality N for VBR
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
6
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Request acknowledge (0=no, 1=all, 2=only for in-band data)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Asks encoder to set CBR (0), VAD(1), DTX(3), VBR(5), VBR+DTX(7)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
8
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
8
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Transmit (8-bit) character to the other end
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
9
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
8
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Intensity stereo information
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
10
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
16
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Announce maximum bit-rate acceptable (N in bytes/second)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
11
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
16
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
reserved
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
12
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
32
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Acknowledge receiving packet N
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
13
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
32
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
reserved
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
14
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
64
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
reserved
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
15
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
64
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
reserved
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
end{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
In-band signalling codes
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "cap:In-band-signalling-codes"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Finally, applications may define custom in-band messages using mode 13.
|
|
The size of the message in bytes is encoded with 5 bits, so that the decoder
|
|
can skip it if it doesn't know how to interpret it.
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
Speech Processing API (
|
|
\emph on
|
|
libspeexdsp
|
|
\emph default
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As of version 1.2beta3, the non-codec parts of the Speex package are now
|
|
in a separate library called
|
|
\emph on
|
|
libspeexdsp
|
|
\emph default
|
|
.
|
|
This library includes the preprocessor, the acoustic echo canceller, the
|
|
jitter buffer, and the resampler.
|
|
In a UNIX environment, it can be linked into a program by adding
|
|
\emph on
|
|
-lspeexdsp -lm
|
|
\emph default
|
|
to the compiler command line.
|
|
Just like for libspeex,
|
|
\series bold
|
|
libspeexdsp calls are reentrant, but not thread-safe
|
|
\series default
|
|
.
|
|
That means that it is fine to use calls from many threads, but
|
|
\series bold
|
|
calls using the same state from multiple threads must be protected by mutexes
|
|
\series default
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Preprocessor
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sub:Preprocessor"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\noindent
|
|
In order to use the Speex preprocessor
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
preprocessor
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, you first need to:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
#include <speex/speex_preprocess.h>
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\noindent
|
|
Then, a preprocessor state can be created as:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
SpeexPreprocessState *preprocess_state = speex_preprocess_state_init(frame_size,
|
|
sampling_rate);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\noindent
|
|
and it is recommended to use the same value for
|
|
\family typewriter
|
|
frame_size
|
|
\family default
|
|
as is used by the encoder (20
|
|
\emph on
|
|
ms
|
|
\emph default
|
|
).
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For each input frame, you need to call:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_preprocess_run(preprocess_state, audio_frame);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\noindent
|
|
where
|
|
\family typewriter
|
|
audio_frame
|
|
\family default
|
|
is used both as input and output.
|
|
In cases where the output audio is not useful for a certain frame, it is
|
|
possible to use instead:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_preprocess_estimate_update(preprocess_state, audio_frame);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\noindent
|
|
This call will update all the preprocessor internal state variables without
|
|
computing the output audio, thus saving some CPU cycles.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The behaviour of the preprocessor can be changed using:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_preprocess_ctl(preprocess_state, request, ptr);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\noindent
|
|
which is used in the same way as the encoder and decoder equivalent.
|
|
Options are listed in Section
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "sub:Preprocessor-options"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The preprocessor state can be destroyed using:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_preprocess_state_destroy(preprocess_state);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Preprocessor options
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sub:Preprocessor-options"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As with the codec, the preprocessor also has options that can be controlled
|
|
using an ioctl()-like call.
|
|
The available options are:
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_DENOISE Turns denoising on(1) or off(0) (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_DENOISE Get denoising status (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_AGC Turns automatic gain control (AGC) on(1) or off(0)
|
|
(
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_AGC Get AGC status (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_VAD Turns voice activity detector (VAD) on(1) or off(0)
|
|
(
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_VAD Get VAD status (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_AGC_LEVEL
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_AGC_LEVEL
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_DEREVERB Turns reverberation removal on(1) or off(0)
|
|
(
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_DEREVERB Get reverberation removal status (
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_DEREVERB_LEVEL Not working yet, do not use
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_DEREVERB_LEVEL Not working yet, do not use
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_DEREVERB_DECAY Not working yet, do not use
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_DEREVERB_DECAY Not working yet, do not use
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_PROB_START
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_PROB_START
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_PROB_CONTINUE
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_PROB_CONTINUE
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_NOISE_SUPPRESS Set maximum attenuation of the noise
|
|
in dB (negative
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_NOISE_SUPPRESS Get maximum attenuation of the noise
|
|
in dB (negative
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_ECHO_SUPPRESS Set maximum attenuation of the residual
|
|
echo in dB (negative
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_ECHO_SUPPRESS Get maximum attenuation of the residual
|
|
echo in dB (negative
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_ECHO_SUPPRESS_ACTIVE Set maximum attenuation of the
|
|
echo in dB when near end is active (negative
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_ECHO_SUPPRESS_ACTIVE Get maximum attenuation of the
|
|
echo in dB when near end is active (negative
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_int32_t
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_SET_ECHO_STATE Set the associated echo canceller for residual
|
|
echo suppression (pointer or NULL for no residual echo suppression)
|
|
\end_layout
|
|
|
|
\begin_layout Description
|
|
SPEEX_PREPROCESS_GET_ECHO_STATE Get the associated echo canceller (pointer)
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Echo Cancellation
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sub:Echo-Cancellation"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The Speex library now includes an echo cancellation
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
echo cancellation
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
algorithm suitable for Acoustic Echo Cancellation
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
acoustic echo cancellation
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(AEC).
|
|
In order to use the echo canceller, you first need to
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
#include <speex/speex_echo.h>
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Then, an echo canceller state can be created by:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
SpeexEchoState *echo_state = speex_echo_state_init(frame_size, filter_length);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
where
|
|
\family typewriter
|
|
frame_size
|
|
\family default
|
|
is the amount of data (in samples) you want to process at once and
|
|
\family typewriter
|
|
filter_length
|
|
\family default
|
|
is the length (in samples) of the echo cancelling filter you want to use
|
|
(also known as
|
|
\shape italic
|
|
tail length
|
|
\shape default
|
|
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
tail length
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
).
|
|
It is recommended to use a frame size in the order of 20 ms (or equal to
|
|
the codec frame size) and make sure it is easy to perform an FFT of that
|
|
size (powers of two are better than prime sizes).
|
|
The recommended tail length is approximately the third of the room reverberatio
|
|
n time.
|
|
For example, in a small room, reverberation time is in the order of 300
|
|
ms, so a tail length of 100 ms is a good choice (800 samples at 8000 Hz
|
|
sampling rate).
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Once the echo canceller state is created, audio can be processed by:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_echo_cancellation(echo_state, input_frame, echo_frame, output_frame);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
where
|
|
\family typewriter
|
|
input_frame
|
|
\family default
|
|
is the audio as captured by the microphone,
|
|
\family typewriter
|
|
echo_frame
|
|
\family default
|
|
is the signal that was played in the speaker (and needs to be removed)
|
|
and
|
|
\family typewriter
|
|
output_frame
|
|
\family default
|
|
is the signal with echo removed.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
One important thing to keep in mind is the relationship between
|
|
\family typewriter
|
|
input_frame
|
|
\family default
|
|
and
|
|
\family typewriter
|
|
echo_frame
|
|
\family default
|
|
.
|
|
It is important that, at any time, any echo that is present in the input
|
|
has already been sent to the echo canceller as
|
|
\family typewriter
|
|
echo_frame
|
|
\family default
|
|
.
|
|
In other words, the echo canceller cannot remove a signal that it hasn't
|
|
yet received.
|
|
On the other hand, the delay between the input signal and the echo signal
|
|
must be small enough because otherwise part of the echo cancellation filter
|
|
is inefficient.
|
|
In the ideal case, you code would look like:
|
|
\begin_inset listings
|
|
lstparams "breaklines=true"
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
write_to_soundcard(echo_frame, frame_size);
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
read_from_soundcard(input_frame, frame_size);
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_echo_cancellation(echo_state, input_frame, echo_frame, output_frame);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
If you wish to further reduce the echo present in the signal, you can do
|
|
so by associating the echo canceller to the preprocessor (see Section
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "sub:Preprocessor"
|
|
|
|
\end_inset
|
|
|
|
).
|
|
This is done by calling:
|
|
\begin_inset listings
|
|
lstparams "breaklines=true"
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_preprocess_ctl(preprocess_state, SPEEX_PREPROCESS_SET_ECHO_STATE,echo_stat
|
|
e);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in the initialisation.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As of version 1.2-beta2, there is an alternative, simpler API that can be
|
|
used instead of
|
|
\emph on
|
|
speex_echo_cancellation()
|
|
\emph default
|
|
.
|
|
When audio capture and playback are handled asynchronously (e.g.
|
|
in different threads or using the
|
|
\emph on
|
|
poll()
|
|
\emph default
|
|
or
|
|
\emph on
|
|
select()
|
|
\emph default
|
|
system call), it can be difficult to keep track of what input_frame comes
|
|
with what echo_frame.
|
|
Instead, the playback context/thread can simply call:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_echo_playback(echo_state, echo_frame);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
every time an audio frame is played.
|
|
Then, the capture context/thread calls:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_echo_capture(echo_state, input_frame, output_frame);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
for every frame captured.
|
|
Internally,
|
|
\emph on
|
|
speex_echo_playback()
|
|
\emph default
|
|
simply buffers the playback frame so it can be used by
|
|
\emph on
|
|
speex_echo_capture()
|
|
\emph default
|
|
to call
|
|
\emph on
|
|
speex_echo_cancel()
|
|
\emph default
|
|
.
|
|
A side effect of using this alternate API is that the playback audio is
|
|
delayed by two frames, which is the normal delay caused by the soundcard.
|
|
When capture and playback are already synchronised,
|
|
\emph on
|
|
speex_echo_cancellation()
|
|
\emph default
|
|
is preferable since it gives better control on the exact input/echo timing.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The echo cancellation state can be destroyed with:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_echo_state_destroy(echo_state);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
It is also possible to reset the state of the echo canceller so it can be
|
|
reused without the need to create another state with:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_echo_state_reset(echo_state);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Troubleshooting
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
There are several things that may prevent the echo canceller from working
|
|
properly.
|
|
One of them is a bug (or something suboptimal) in the code, but there are
|
|
many others you should consider first
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Using a different soundcard to do the capture and plaback will
|
|
\series bold
|
|
not
|
|
\series default
|
|
work, regardless of what you may think.
|
|
The only exception to that is if the two cards can be made to have their
|
|
sampling clock
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
locked
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
on the same clock source.
|
|
If not, the clocks will always have a small amount of drift, which will
|
|
prevent the echo canceller from adapting.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
The delay between the record and playback signals must be minimal.
|
|
Any signal played has to
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
appear
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
on the playback (far end) signal slightly before the echo canceller
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
sees
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
it in the near end signal, but excessive delay means that part of the filter
|
|
length is wasted.
|
|
In the worst situations, the delay is such that it is longer than the filter
|
|
length, in which case, no echo can be cancelled.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
When it comes to echo tail length (filter length), longer is
|
|
\series bold
|
|
not
|
|
\series default
|
|
better.
|
|
Actually, the longer the tail length, the longer it takes for the filter
|
|
to adapt.
|
|
Of course, a tail length that is too short will not cancel enough echo,
|
|
but the most common problem seen is that people set a very long tail length
|
|
and then wonder why no echo is being cancelled.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Non-linear distortion cannot (by definition) be modeled by the linear adaptive
|
|
filter used in the echo canceller and thus cannot be cancelled.
|
|
Use good audio gear and avoid saturation/clipping.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Also useful is reading
|
|
\emph on
|
|
Echo Cancellation Demystified
|
|
\emph default
|
|
by Alexey Frunze
|
|
\begin_inset Foot
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
http://www.embeddedstar.com/articles/2003/7/article20030720-1.html
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
, which explains the fundamental principles of echo cancellation.
|
|
The details of the algorithm described in the article are different, but
|
|
the general ideas of echo cancellation through adaptive filters are the
|
|
same.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As of version 1.2beta2, a new
|
|
\family typewriter
|
|
echo_diagnostic.m
|
|
\family default
|
|
tool is included in the source distribution.
|
|
The first step is to define DUMP_ECHO_CANCEL_DATA during the build.
|
|
This causes the echo canceller to automatically save the near-end, far-end
|
|
and output signals to files (aec_rec.sw aec_play.sw and aec_out.sw).
|
|
These are exactly what the AEC receives and outputs.
|
|
From there, it is necessary to start Octave and type:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
lstparams "language=Matlab"
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
echo_diagnostic('aec_rec.sw', 'aec_play.sw', 'aec_diagnostic.sw', 1024);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The value of 1024 is the filter length and can be changed.
|
|
There will be some (hopefully) useful messages printed and echo cancelled
|
|
audio will be saved to aec_diagnostic.sw .
|
|
If even that output is bad (almost no cancellation) then there is probably
|
|
problem with the playback or recording process.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Jitter Buffer
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The jitter buffer can be enabled by including:
|
|
\begin_inset listings
|
|
lstparams "breaklines=true"
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
#include <speex/speex_jitter.h>
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
and a new jitter buffer state can be initialised by:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
lstparams "breaklines=true"
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
JitterBuffer *state = jitter_buffer_init(step);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
where the
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
step
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
argument is the default time step (in timestamp units) used for adjusting
|
|
the delay and doing concealment.
|
|
A value of 1 is always correct, but higher values may be more convenient
|
|
sometimes.
|
|
For example, if you are only able to do concealment on 20ms frames, there
|
|
is no point in the jitter buffer asking you to do it on one sample.
|
|
Another example is that for video, it makes no sense to adjust the delay
|
|
by less than a full frame.
|
|
The value provided can always be changed at a later time.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The jitter buffer API is based on the
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
JitterBufferPacket
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
type, which is defined as:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
typedef struct {
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
char *data; /* Data bytes contained in the packet */
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_uint32_t len; /* Length of the packet in bytes */
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_uint32_t timestamp; /* Timestamp for the packet */
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
spx_uint32_t span; /* Time covered by the packet (timestamp units)
|
|
*/
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
} JitterBufferPacket;
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
As an example, for audio the timestamp field would be what is obtained from
|
|
the RTP timestamp field and the span would be the number of samples that
|
|
are encoded in the packet.
|
|
For Speex narrowband, span would be 160 if only one frame is included in
|
|
the packet.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
When a packet arrives, it need to be inserter into the jitter buffer by:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
JitterBufferPacket packet;
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
/* Fill in each field in the packet struct */
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
jitter_buffer_put(state, &packet);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
When the decoder is ready to decode a packet the packet to be decoded can
|
|
be obtained by:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
int start_offset;
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
err = jitter_buffer_get(state, &packet, desired_span, &start_offset);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
If
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
jitter_buffer_put()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
and
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
jitter_buffer_get()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
are called from different threads, then
|
|
\series bold
|
|
you need to protect the jitter buffer state with a mutex
|
|
\series default
|
|
.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Because the jitter buffer is designed not to use an explicit timer, it needs
|
|
to be told about the time explicitly.
|
|
This is done by calling:
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
jitter_buffer_tick(state);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This needs to be done periodically in the playing thread.
|
|
This will be the last jitter buffer call before going to sleep (until more
|
|
data is played back).
|
|
In some cases, it may be preferable to use
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
jitter_buffer_remaining_span(state, remaining);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The second argument is used to specify that we are still holding data that
|
|
has not been written to the playback device.
|
|
For instance, if 256 samples were needed by the soundcard (specified by
|
|
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
desired_span
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
), but
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
jitter_buffer_get()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
returned 320 samples, we would have
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
remaining=64
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Resampler
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Speex includes a resampling modules.
|
|
To make use of the resampler, it is necessary to include its header file:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
#include <speex/speex_resampler.h>
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For each stream that is to be resampled, it is necessary to create a resampler
|
|
state with:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
SpeexResamplerState *resampler;
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
resampler = speex_resampler_init(nb_channels, input_rate, output_rate, quality,
|
|
&err);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
where
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
nb_channels
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
is the number of channels that will be used (either interleaved or non-interlea
|
|
ved),
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
input_rate
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
is the sampling rate of the input stream,
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
output_rate
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
is the sampling rate of the output stream and
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
quality
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
is the requested quality setting (0 to 10).
|
|
The quality parameter is useful for controlling the quality/complexity/latency
|
|
tradeoff.
|
|
Using a higher quality setting means less noise/aliasing, a higher complexity
|
|
and a higher latency.
|
|
Usually, a quality of 3 is acceptable for most desktop uses and quality
|
|
10 is mostly recommended for pro audio work.
|
|
Quality 0 usually has a decent sound (certainly better than using linear
|
|
interpolation resampling), but artifacts may be heard.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The actual resampling is performed using
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset listings
|
|
inline false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
err = speex_resampler_process_int(resampler, channelID, in, &in_length,
|
|
out, &out_length);
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
where
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
channelID
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
is the ID of the channel to be processed.
|
|
For a mono stream, use 0.
|
|
The
|
|
\emph on
|
|
in
|
|
\emph default
|
|
pointer points to the first sample of the input buffer for the selected
|
|
channel and
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
out
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
points to the first sample of the output.
|
|
The size of the input and output buffers are specified by
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
in_length
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
and
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
out_length
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
respectively.
|
|
Upon completion, these values are replaced by the number of samples read
|
|
and written by the resampler.
|
|
Unless an error occurs, either all input samples will be read or all output
|
|
samples will be written to (or both).
|
|
For floating-point samples, the function
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_resampler_process_float()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
behaves similarly.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
It is also possible to process multiple channels at once.
|
|
To do that, you can use speex_resampler_process_interleaved_int() or
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_resampler_process_interleaved_float()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
The arguments are the same except that there is no
|
|
\begin_inset listings
|
|
inline true
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
channelID
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
argument.
|
|
Note that the
|
|
\series bold
|
|
length parameters are per-channel
|
|
\series default
|
|
.
|
|
So if you have 1024 samples for each of 4 channels, you pass 1024 and not
|
|
4096.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The resampler allows changing the quality and input/output sampling frequencies
|
|
on the fly without glitches.
|
|
This can be done with calls such as
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_resampler_set_quality()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
and
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_resampler_set_rate()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
The only side effect is that a new filter will have to be recomputed, consuming
|
|
many CPU cycles.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
When resampling a file, it is often desirable to have the output file perfectly
|
|
synchronised with the input.
|
|
To do that, you need to call
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_resampler_skip_zeros()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\series bold
|
|
before
|
|
\series default
|
|
you start processing any samples.
|
|
For real-time applications (e.g.
|
|
VoIP), it is not recommended to do that as the first process frame will
|
|
be shorter to compensate for the delay (the skipped zeros).
|
|
Instead, in real-time applications you may want to know how many delay
|
|
is introduced by the resampler.
|
|
This can be done at run-time with
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_resampler_get_input_latency()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
and
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_resampler_get_output_latency()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
functions.
|
|
First function returns delay measured in samples at input samplerate, while
|
|
second returns delay measured in samples at output samplerate.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
To destroy a resampler state, just call
|
|
\begin_inset listings
|
|
inline true
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
speex_resampler_destroy()
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Ring Buffer
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In some cases, it is necessary to interface components that use different
|
|
block sizes.
|
|
For example, it is possible that the soundcard does not support reading/writing
|
|
in blocks of 20
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
ms or sometimes, complicated resampling ratios mean that the blocks don't
|
|
always have the same time.
|
|
In thoses cases, it is often necessary to buffer a bit of audio using a
|
|
ring buffer.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
Formats and standards
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
standards
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:Formats-and-standards"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Speex can encode speech in both narrowband and wideband and provides different
|
|
bit-rates.
|
|
However, not all features need to be supported by a certain implementation
|
|
or device.
|
|
In order to be called
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
Speex compatible
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
(whatever that means), an implementation must implement at least a basic
|
|
set of features.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
At the minimum, all narrowband modes of operation MUST be supported at the
|
|
decoder.
|
|
This includes the decoding of a wideband bit-stream by the narrowband decoder
|
|
\begin_inset Foot
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
The wideband bit-stream contains an embedded narrowband bit-stream which
|
|
can be decoded alone
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
If present, a wideband decoder MUST be able to decode a narrowband stream,
|
|
and MAY either be able to decode all wideband modes or be able to decode
|
|
the embedded narrowband part of all modes (which includes ignoring the
|
|
high-band bits).
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For encoders, at least one narrowband or wideband mode MUST be supported.
|
|
The main reason why all encoding modes do not have to be supported is that
|
|
some platforms may not be able to handle the complexity of encoding in
|
|
some modes.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
RTP
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
RTP
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
Payload Format
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The RTP payload draft is included in appendix
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "sec:IETF-draft"
|
|
|
|
\end_inset
|
|
|
|
and the latest version is available at
|
|
\begin_inset Flex URL
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
http://www.speex.org/drafts/latest
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
This draft has been sent (2003/02/26) to the Internet Engineering Task
|
|
Force (IETF) and will be discussed at the March 18th meeting in San Francisco.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
MIME Type
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For now, you should use the MIME type audio/x-speex for Speex-in-Ogg.
|
|
We will apply for type
|
|
\family typewriter
|
|
audio/speex
|
|
\family default
|
|
in the near future.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Ogg
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
Ogg
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
file format
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Speex bit-streams can be stored in Ogg files.
|
|
In this case, the first packet of the Ogg file contains the Speex header
|
|
described in table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:ogg_speex_header"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
All integer fields in the headers are stored as little-endian.
|
|
The
|
|
\family typewriter
|
|
speex_string
|
|
\family default
|
|
field must contain the
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
|
|
\family typewriter
|
|
Speex
|
|
\family default
|
|
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
|
|
\begin_inset space ~
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
(with 3 trailing spaces), which identifies the bit-stream.
|
|
The next field,
|
|
\family typewriter
|
|
speex_version
|
|
\family default
|
|
contains the version of Speex that encoded the file.
|
|
For now, refer to speex_header.[ch] for more info.
|
|
The
|
|
\emph on
|
|
beginning of stream
|
|
\emph default
|
|
(
|
|
\family typewriter
|
|
b_o_s
|
|
\family default
|
|
) flag is set to 1 for the header.
|
|
The header packet has
|
|
\family typewriter
|
|
packetno=0
|
|
\family default
|
|
and
|
|
\family typewriter
|
|
granulepos=0
|
|
\family default
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The second packet contains the Speex comment header.
|
|
The format used is the Vorbis comment format described here: http://www.xiph.org/
|
|
ogg/vorbis/doc/v-comment.html .
|
|
This packet has
|
|
\family typewriter
|
|
packetno=1
|
|
\family default
|
|
and
|
|
\family typewriter
|
|
granulepos=0
|
|
\family default
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The third and subsequent packets each contain one or more (number found
|
|
in header) Speex frames.
|
|
These are identified with
|
|
\family typewriter
|
|
packetno
|
|
\family default
|
|
starting from 2 and the
|
|
\family typewriter
|
|
granulepos
|
|
\family default
|
|
is the number of the last sample encoded in that packet.
|
|
The last of these packets has the
|
|
\emph on
|
|
end of stream
|
|
\emph default
|
|
(
|
|
\family typewriter
|
|
e_o_s
|
|
\family default
|
|
) flag is set to 1.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float table
|
|
placement htbp
|
|
wide true
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="16" columns="3">
|
|
<features>
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Field
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Type
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Size
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
speex_string
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
char[]
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
8
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
speex_version
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
char[]
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
20
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
speex_version_id
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
int
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
header_size
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
int
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
rate
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
int
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
mode
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
int
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
mode_bitstream_version
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
int
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
nb_channels
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
int
|
|
\end_layout
|
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\end_inset
|
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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4
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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bitrate
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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int
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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4
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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int
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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4
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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vbr
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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int
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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4
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\end_layout
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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frames_per_packet
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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int
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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4
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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extra_headers
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\end_layout
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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int
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\end_layout
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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4
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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reserved1
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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int
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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4
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\end_inset
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</cell>
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</row>
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<row>
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<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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int
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\end_inset
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</cell>
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<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
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\begin_inset Text
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\begin_layout Plain Layout
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4
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\end_layout
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\end_inset
|
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</cell>
|
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</row>
|
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</lyxtabular>
|
|
|
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\end_inset
|
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\begin_inset ERT
|
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status collapsed
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\begin_layout Plain Layout
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\backslash
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end{center}
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\end_layout
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\end_inset
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\end_layout
|
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|
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\begin_layout Plain Layout
|
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\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
Ogg/Speex header packet
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "cap:ogg_speex_header"
|
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|
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\end_inset
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\end_layout
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\end_inset
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\end_layout
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\begin_layout Standard
|
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\begin_inset ERT
|
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status collapsed
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\begin_layout Plain Layout
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\backslash
|
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clearpage
|
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\end_layout
|
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\end_inset
|
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|
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\end_layout
|
|
|
|
\begin_layout Chapter
|
|
Introduction to CELP Coding
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
CELP
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:Introduction-to-CELP"
|
|
|
|
\end_inset
|
|
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|
|
|
\end_layout
|
|
|
|
\begin_layout Quote
|
|
\align center
|
|
|
|
\emph on
|
|
Do not meddle in the affairs of poles, for they are subtle and quick to
|
|
leave the unit circle.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Speex is based on CELP, which stands for Code Excited Linear Prediction.
|
|
This section attempts to introduce the principles behind CELP, so if you
|
|
are already familiar with CELP, you can safely skip to section
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "sec:Speex-narrowband-mode"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
The CELP technique is based on three ideas:
|
|
\end_layout
|
|
|
|
\begin_layout Enumerate
|
|
The use of a linear prediction (LP) model to model the vocal tract
|
|
\end_layout
|
|
|
|
\begin_layout Enumerate
|
|
The use of (adaptive and fixed) codebook entries as input (excitation) of
|
|
the LP model
|
|
\end_layout
|
|
|
|
\begin_layout Enumerate
|
|
The search performed in closed-loop in a
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
perceptually weighted domain
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This section describes the basic ideas behind CELP.
|
|
This is still a work in progress.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Source-Filter Model of Speech Prediction
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The source-filter model of speech production assumes that the vocal cords
|
|
are the source of spectrally flat sound (the excitation signal), and that
|
|
the vocal tract acts as a filter to spectrally shape the various sounds
|
|
of speech.
|
|
While still an approximation, the model is widely used in speech coding
|
|
because of its simplicity.Its use is also the reason why most speech codecs
|
|
(Speex included) perform badly on music signals.
|
|
The different phonemes can be distinguished by their excitation (source)
|
|
and spectral shape (filter).
|
|
Voiced sounds (e.g.
|
|
vowels) have an excitation signal that is periodic and that can be approximated
|
|
by an impulse train in the time domain or by regularly-spaced harmonics
|
|
in the frequency domain.
|
|
On the other hand, fricatives (such as the "s", "sh" and "f" sounds) have
|
|
an excitation signal that is similar to white Gaussian noise.
|
|
So called voice fricatives (such as "z" and "v") have excitation signal
|
|
composed of an harmonic part and a noisy part.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The source-filter model is usually tied with the use of Linear prediction.
|
|
The CELP model is based on source-filter model, as can be seen from the
|
|
CELP decoder illustrated in Figure
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "fig:The-CELP-model"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Graphics
|
|
filename celp_decoder.eps
|
|
width 45page%
|
|
keepAspectRatio
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
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\begin_layout Plain Layout
|
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\backslash
|
|
end{center}
|
|
\end_layout
|
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|
|
\end_inset
|
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|
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\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
The CELP model of speech synthesis (decoder)
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "fig:The-CELP-model"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
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|
|
\end_layout
|
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|
|
\end_inset
|
|
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|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Linear Prediction Coefficients (LPC)
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
linear prediction
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Linear prediction is at the base of many speech coding techniques, including
|
|
CELP.
|
|
The idea behind it is to predict the signal
|
|
\begin_inset Formula $x[n]$
|
|
\end_inset
|
|
|
|
using a linear combination of its past samples:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Formula \[
|
|
y[n]=\sum_{i=1}^{N}a_{i}x[n-i]\]
|
|
|
|
\end_inset
|
|
|
|
where
|
|
\begin_inset Formula $y[n]$
|
|
\end_inset
|
|
|
|
is the linear prediction of
|
|
\begin_inset Formula $x[n]$
|
|
\end_inset
|
|
|
|
.
|
|
The prediction error is thus given by:
|
|
\begin_inset Formula \[
|
|
e[n]=x[n]-y[n]=x[n]-\sum_{i=1}^{N}a_{i}x[n-i]\]
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The goal of the LPC analysis is to find the best prediction coefficients
|
|
|
|
\begin_inset Formula $a_{i}$
|
|
\end_inset
|
|
|
|
which minimize the quadratic error function:
|
|
\begin_inset Formula \[
|
|
E=\sum_{n=0}^{L-1}\left[e[n]\right]^{2}=\sum_{n=0}^{L-1}\left[x[n]-\sum_{i=1}^{N}a_{i}x[n-i]\right]^{2}\]
|
|
|
|
\end_inset
|
|
|
|
That can be done by making all derivatives
|
|
\begin_inset Formula $\frac{\partial E}{\partial a_{i}}$
|
|
\end_inset
|
|
|
|
equal to zero:
|
|
\begin_inset Formula \[
|
|
\frac{\partial E}{\partial a_{i}}=\frac{\partial}{\partial a_{i}}\sum_{n=0}^{L-1}\left[x[n]-\sum_{i=1}^{N}a_{i}x[n-i]\right]^{2}=0\]
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For an order
|
|
\begin_inset Formula $N$
|
|
\end_inset
|
|
|
|
filter, the filter coefficients
|
|
\begin_inset Formula $a_{i}$
|
|
\end_inset
|
|
|
|
are found by solving the system
|
|
\begin_inset Formula $N\times N$
|
|
\end_inset
|
|
|
|
linear system
|
|
\begin_inset Formula $\mathbf{Ra}=\mathbf{r}$
|
|
\end_inset
|
|
|
|
, where
|
|
\begin_inset Formula \[
|
|
\mathbf{R}=\left[\begin{array}{cccc}
|
|
R(0) & R(1) & \cdots & R(N-1)\\
|
|
R(1) & R(0) & \cdots & R(N-2)\\
|
|
\vdots & \vdots & \ddots & \vdots\\
|
|
R(N-1) & R(N-2) & \cdots & R(0)\end{array}\right]\]
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Formula \[
|
|
\mathbf{r}=\left[\begin{array}{c}
|
|
R(1)\\
|
|
R(2)\\
|
|
\vdots\\
|
|
R(N)\end{array}\right]\]
|
|
|
|
\end_inset
|
|
|
|
with
|
|
\begin_inset Formula $R(m)$
|
|
\end_inset
|
|
|
|
, the auto-correlation
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
auto-correlation
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
of the signal
|
|
\begin_inset Formula $x[n]$
|
|
\end_inset
|
|
|
|
, computed as:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Formula \[
|
|
R(m)=\sum_{i=0}^{N-1}x[i]x[i-m]\]
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Because
|
|
\begin_inset Formula $\mathbf{R}$
|
|
\end_inset
|
|
|
|
is Hermitian Toeplitz, the Levinson-Durbin
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
Levinson-Durbin
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
algorithm can be used, making the solution to the problem
|
|
\begin_inset Formula $\mathcal{O}\left(N^{2}\right)$
|
|
\end_inset
|
|
|
|
instead of
|
|
\begin_inset Formula $\mathcal{O}\left(N^{3}\right)$
|
|
\end_inset
|
|
|
|
.
|
|
Also, it can be proven that all the roots of
|
|
\begin_inset Formula $A(z)$
|
|
\end_inset
|
|
|
|
are within the unit circle, which means that
|
|
\begin_inset Formula $1/A(z)$
|
|
\end_inset
|
|
|
|
is always stable.
|
|
This is in theory; in practice because of finite precision, there are two
|
|
commonly used techniques to make sure we have a stable filter.
|
|
First, we multiply
|
|
\begin_inset Formula $R(0)$
|
|
\end_inset
|
|
|
|
by a number slightly above one (such as 1.0001), which is equivalent to
|
|
adding noise to the signal.
|
|
Also, we can apply a window to the auto-correlation, which is equivalent
|
|
to filtering in the frequency domain, reducing sharp resonances.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Pitch Prediction
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
pitch
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
During voiced segments, the speech signal is periodic, so it is possible
|
|
to take advantage of that property by approximating the excitation signal
|
|
|
|
\begin_inset Formula $e[n]$
|
|
\end_inset
|
|
|
|
by a gain times the past of the excitation:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Formula \[
|
|
e[n]\simeq p[n]=\beta e[n-T]\ ,\]
|
|
|
|
\end_inset
|
|
|
|
where
|
|
\begin_inset Formula $T$
|
|
\end_inset
|
|
|
|
is the pitch period,
|
|
\begin_inset Formula $\beta$
|
|
\end_inset
|
|
|
|
is the pitch gain.
|
|
We call that long-term prediction since the excitation is predicted from
|
|
|
|
\begin_inset Formula $e[n-T]$
|
|
\end_inset
|
|
|
|
with
|
|
\begin_inset Formula $T\gg N$
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Innovation Codebook
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The final excitation
|
|
\begin_inset Formula $e[n]$
|
|
\end_inset
|
|
|
|
will be the sum of the pitch prediction and an
|
|
\emph on
|
|
innovation
|
|
\emph default
|
|
signal
|
|
\begin_inset Formula $c[n]$
|
|
\end_inset
|
|
|
|
taken from a fixed codebook, hence the name
|
|
\emph on
|
|
Code
|
|
\emph default
|
|
Excited Linear Prediction.
|
|
The final excitation is given by
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Formula \[
|
|
e[n]=p[n]+c[n]=\beta e[n-T]+c[n]\ .\]
|
|
|
|
\end_inset
|
|
|
|
The quantization of
|
|
\begin_inset Formula $c[n]$
|
|
\end_inset
|
|
|
|
is where most of the bits in a CELP codec are allocated.
|
|
It represents the information that couldn't be obtained either from linear
|
|
prediction or pitch prediction.
|
|
In the
|
|
\emph on
|
|
z
|
|
\emph default
|
|
-domain we can represent the final signal
|
|
\begin_inset Formula $X(z)$
|
|
\end_inset
|
|
|
|
as
|
|
\begin_inset Formula \[
|
|
X(z)=\frac{C(z)}{A(z)\left(1-\beta z^{-T}\right)}\]
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Noise Weighting
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
error weighting
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
analysis-by-synthesis
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Most (if not all) modern audio codecs attempt to
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
shape
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
the noise so that it appears mostly in the frequency regions where the
|
|
ear cannot detect it.
|
|
For example, the ear is more tolerant to noise in parts of the spectrum
|
|
that are louder and
|
|
\emph on
|
|
vice versa
|
|
\emph default
|
|
.
|
|
In order to maximize speech quality, CELP codecs minimize the mean square
|
|
of the error (noise) in the perceptually weighted domain.
|
|
This means that a perceptual noise weighting filter
|
|
\begin_inset Formula $W(z)$
|
|
\end_inset
|
|
|
|
is applied to the error signal in the encoder.
|
|
In most CELP codecs,
|
|
\begin_inset Formula $W(z)$
|
|
\end_inset
|
|
|
|
is a pole-zero weighting filter derived from the linear prediction coefficients
|
|
(LPC), generally using bandwidth expansion.
|
|
Let the spectral envelope be represented by the synthesis filter
|
|
\begin_inset Formula $1/A(z)$
|
|
\end_inset
|
|
|
|
, CELP codecs typically derive the noise weighting filter as
|
|
\begin_inset Formula \begin{equation}
|
|
W(z)=\frac{A(z/\gamma_{1})}{A(z/\gamma_{2})}\ ,\label{eq:gamma-weighting}\end{equation}
|
|
|
|
\end_inset
|
|
|
|
where
|
|
\begin_inset Formula $\gamma_{1}=0.9$
|
|
\end_inset
|
|
|
|
and
|
|
\begin_inset Formula $\gamma_{2}=0.6$
|
|
\end_inset
|
|
|
|
in the Speex reference implementation.
|
|
If a filter
|
|
\begin_inset Formula $A(z)$
|
|
\end_inset
|
|
|
|
has (complex) poles at
|
|
\begin_inset Formula $p_{i}$
|
|
\end_inset
|
|
|
|
in the
|
|
\begin_inset Formula $z$
|
|
\end_inset
|
|
|
|
-plane, the filter
|
|
\begin_inset Formula $A(z/\gamma)$
|
|
\end_inset
|
|
|
|
will have its poles at
|
|
\begin_inset Formula $p'_{i}=\gamma p_{i}$
|
|
\end_inset
|
|
|
|
, making it a flatter version of
|
|
\begin_inset Formula $A(z)$
|
|
\end_inset
|
|
|
|
.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The weighting filter is applied to the error signal used to optimize the
|
|
codebook search through analysis-by-synthesis (AbS).
|
|
This results in a spectral shape of the noise that tends towards
|
|
\begin_inset Formula $1/W(z)$
|
|
\end_inset
|
|
|
|
.
|
|
While the simplicity of the model has been an important reason for the
|
|
success of CELP, it remains that
|
|
\begin_inset Formula $W(z)$
|
|
\end_inset
|
|
|
|
is a very rough approximation for the perceptually optimal noise weighting
|
|
function.
|
|
Fig.
|
|
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:Standard-noise-shaping"
|
|
|
|
\end_inset
|
|
|
|
illustrates the noise shaping that results from Eq.
|
|
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "eq:gamma-weighting"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
Throughout this paper, we refer to
|
|
\begin_inset Formula $W(z)$
|
|
\end_inset
|
|
|
|
as the noise weighting filter and to
|
|
\begin_inset Formula $1/W(z)$
|
|
\end_inset
|
|
|
|
as the noise shaping filter (or curve).
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Graphics
|
|
filename ref_shaping.eps
|
|
width 45page%
|
|
keepAspectRatio
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
end{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
Standard noise shaping in CELP.
|
|
Arbitrary y-axis offset.
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "cap:Standard-noise-shaping"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Analysis-by-Synthesis
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
One of the main principles behind CELP is called Analysis-by-Synthesis (AbS),
|
|
meaning that the encoding (analysis) is performed by perceptually optimising
|
|
the decoded (synthesis) signal in a closed loop.
|
|
In theory, the best CELP stream would be produced by trying all possible
|
|
bit combinations and selecting the one that produces the best-sounding
|
|
decoded signal.
|
|
This is obviously not possible in practice for two reasons: the required
|
|
complexity is beyond any currently available hardware and the
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
best sounding
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
selection criterion implies a human listener.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In order to achieve real-time encoding using limited computing resources,
|
|
the CELP optimisation is broken down into smaller, more manageable, sequential
|
|
searches using the perceptual weighting function described earlier.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
The Speex Decoder Specification
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Narrowband decoder
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
<Insert decoder figure here>
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Narrowband modes
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
There are 7 different narrowband bit-rates defined for Speex, ranging from
|
|
250 bps to 24.6 kbps, although the modes below 5.9 kbps should not be used
|
|
for speech.
|
|
The bit-allocation for each mode is detailed in table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:bits-narrowband"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
Each frame starts with the mode ID encoded with 4 bits which allows a range
|
|
from 0 to 15, though only the first 7 values are used (the others are reserved).
|
|
The parameters are listed in the table in the order they are packed in
|
|
the bit-stream.
|
|
All frame-based parameters are packed before sub-frame parameters.
|
|
The parameters for a certain sub-frame are all packed before the following
|
|
sub-frame is packed.
|
|
The
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
OL
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
in the parameter description means that the parameter is an open loop estimatio
|
|
n based on the whole frame.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float table
|
|
placement h
|
|
wide true
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="12" columns="11">
|
|
<features>
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Parameter
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Update rate
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
2
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
6
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
8
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Wideband bit
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Mode ID
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
LSP
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
18
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
18
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
18
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
18
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
30
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
30
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
30
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
18
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
OL pitch
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
OL pitch gain
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
OL Exc gain
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Fine pitch
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
sub-frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Pitch gain
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
sub-frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Innovation gain
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
sub-frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Innovation VQ
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
sub-frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
16
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
20
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
35
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
48
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
64
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
96
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
10
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Total
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
43
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
119
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
160
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
220
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
300
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
364
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
492
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
79
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
end{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
Bit allocation for narrowband modes
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "cap:bits-narrowband"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
LSP decoding
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Depending on the mode, LSP parameters are encoded using either 18 bits or
|
|
30 bits.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Interpolation
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Safe margin
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Adaptive codebook
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For rates of 8 kbit/s and above, the pitch period is encoded for each subframe.
|
|
The real period is
|
|
\begin_inset Formula $T=p_{i}+17$
|
|
\end_inset
|
|
|
|
where
|
|
\begin_inset Formula $p_{i}$
|
|
\end_inset
|
|
|
|
is a value encoded with 7 bits and 17 corresponds to the minimum pitch.
|
|
The maximum period is 144.
|
|
At 5.95 kbit/s (mode 2), the pitch period is similarly encoded, but only
|
|
once for the frame.
|
|
Each sub-frame then has a 2-bit offset that is added to the pitch value
|
|
of the frame.
|
|
In that case, the pitch for each sub-frame is equal to
|
|
\begin_inset Formula $T-1+offset$
|
|
\end_inset
|
|
|
|
.
|
|
For rates below 5.95 kbit/s, only the per-frame pitch is used and the pitch
|
|
is constant for all sub-frames.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Speex uses a 3-tap predictor for rates of 5.95 kbit/s and above.
|
|
The three gain values are obtained from a 5-bit or a 7-bit codebook, depending
|
|
on the mode.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Innovation codebook
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Split codebook, size and entries depend on bit-rate
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
a 5-bit gain is encoder on a per-frame basis
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Depending on the mode, higher resolution per sub-frame
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
innovation sub-vectors concatenated, gain applied
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Perceptual enhancement
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Optional, implementation-defined.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Bit-stream definition
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This section defines the bit-stream that is transmitted on the wire.
|
|
One speex packet consist of 1 frame header and 4 sub-frames:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="1" columns="5">
|
|
<features>
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Frame Header
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Subframe 1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Subframe2
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Subframe 3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Subframe 4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The frame header is variable length, depending on decoding mode and submode.
|
|
The narrowband frame header is defined as follows:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="1" columns="6">
|
|
<features>
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
wb bit
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
modeid
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
LSP
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
OL-pitch
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
OL-pitchgain
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
OL ExcGain
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
wb-bit: Wideband bit (1 bit) 0=narrowband, 1=wideband
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
modeid: Mode identifier (4 bits)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
LSP: Line Spectral Pairs (0, 18 or 30 bits)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
OL-pitch: Open Loop Pitch (0 or 7 bits)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
OL-pitchgain: Open Loop Pitch Gain (0 or 4 bits)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
OL-ExcGain: Open Loop Excitation Gain (0 or 5 bits)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
...
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Each subframe is defined as follows:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="1" columns="4">
|
|
<features>
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<column alignment="center" valignment="top" width="0">
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
FinePitch
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
PitchGain
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
InnovationGain
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Innovation VQ
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
FinePitch: (0 or 7 bits)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
PitchGain: (0, 5, or 7 bits)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Innovation Gain: (0, 1, 3 bits)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Innovation VQ: (0-96 bits)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
...
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Sample decoder
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This section contains some sample source code, showing how a basic Speex
|
|
decoder can be implemented.
|
|
The sample decoder is narrowband submode 3 only, and with no advanced features
|
|
like enhancement, vbr etc.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
...
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "nb_celp.c"
|
|
lstparams "caption={Sample Decoder}"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Subsection
|
|
Lookup tables
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The Speex decoder includes a set of lookup tables and codebooks, which are
|
|
used to convert between values of different domains.
|
|
This includes:
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
- Excitation 10x16 (3200 bps)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
- Excitation 10x32 (4000 bps)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
- Excitation 20x32 (2000 bps)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
- Excitation 5x256 (12800 bps)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
- Excitation 5x64 (9600 bps)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
- Excitation 8x128 (7000 bps)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
- Codebook for 3-tap pitch prediction gain (Normal and Low Bitrate)
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
- Codebook for LSPs in narrowband CELP mode
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
...
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The exact lookup tables are included here for reference.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "../libspeex/exc_5_64_table.c"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "../libspeex/exc_5_256_table.c"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "../libspeex/exc_8_128_table.c"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "../libspeex/exc_10_16_table.c"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "../libspeex/exc_10_32_table.c"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "../libspeex/exc_20_32_table.c"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "../libspeex/gain_table.c"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "../libspeex/gain_table_lbr.c"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "../libspeex/lsp_tables_nb.c"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Wideband embedded decoder
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
QMF filter.
|
|
Narrowband signal decoded using narrowband decoder
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For the high band, the decoder is similar to the narrowband decoder, with
|
|
the main difference being that there is no adaptive codebook.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Gain is per-subframe
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
Speex narrowband mode
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:Speex-narrowband-mode"
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
narrowband
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This section looks at how Speex works for narrowband (
|
|
\begin_inset Formula $8\:\mathrm{kHz}$
|
|
\end_inset
|
|
|
|
sampling rate) operation.
|
|
The frame size for this mode is
|
|
\begin_inset Formula $20\:\mathrm{ms}$
|
|
\end_inset
|
|
|
|
, corresponding to 160 samples.
|
|
Each frame is also subdivided into 4 sub-frames of 40 samples each.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Also many design decisions were based on the original goals and assumptions:
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Minimizing the amount of information extracted from past frames (for robustness
|
|
to packet loss)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
Dynamically-selectable codebooks (LSP, pitch and innovation)
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
sub-vector fixed (innovation) codebooks
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Whole-Frame Analysis
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
linear prediction
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In narrowband, Speex frames are 20 ms long (160 samples) and are subdivided
|
|
in 4 sub-frames of 5 ms each (40 samples).
|
|
For most narrowband bit-rates (8 kbps and above), the only parameters encoded
|
|
at the frame level are the Line Spectral Pairs (LSP) and a global excitation
|
|
gain
|
|
\begin_inset Formula $g_{frame}$
|
|
\end_inset
|
|
|
|
, as shown in Fig.
|
|
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:Frame-open-loop-analysis"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
All other parameters are encoded at the sub-frame level.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Linear prediction analysis is performed once per frame using an asymmetric
|
|
Hamming window centered on the fourth sub-frame.
|
|
Because linear prediction coefficients (LPC) are not robust to quantization,
|
|
they are first converted to line spectral pairs (LSP)
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
line spectral pair
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
.
|
|
The LSP's are considered to be associated to the
|
|
\begin_inset Formula $4^{th}$
|
|
\end_inset
|
|
|
|
sub-frames and the LSP's associated to the first 3 sub-frames are linearly
|
|
interpolated using the current and previous LSP coefficients.
|
|
The LSP coefficients and converted back to the LPC filter
|
|
\begin_inset Formula $\hat{A}(z)$
|
|
\end_inset
|
|
|
|
.
|
|
The non-quantized interpolated filter is denoted
|
|
\begin_inset Formula $A(z)$
|
|
\end_inset
|
|
|
|
and can be used for the weighting filter
|
|
\begin_inset Formula $W(z)$
|
|
\end_inset
|
|
|
|
because it does not need to be available to the decoder.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
To make Speex more robust to packet loss, no prediction is applied on the
|
|
LSP coefficients prior to quantization.
|
|
The LSPs are encoded using vector quantization (VQ) with 30 bits for higher
|
|
quality modes and 18 bits for lower quality.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Graphics
|
|
filename speex_analysis.eps
|
|
width 35page%
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
end{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
Frame open-loop analysis
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "cap:Frame-open-loop-analysis"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Sub-Frame Analysis-by-Synthesis
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float figure
|
|
wide false
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Graphics
|
|
filename speex_abs.eps
|
|
lyxscale 75
|
|
width 40page%
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
end{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
Analysis-by-synthesis closed-loop optimization on a sub-frame.
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "cap:Sub-frame-AbS"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The analysis-by-synthesis (AbS) encoder loop is described in Fig.
|
|
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:Sub-frame-AbS"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
There are three main aspects where Speex significantly differs from most
|
|
other CELP codecs.
|
|
First, while most recent CELP codecs make use of fractional pitch estimation
|
|
with a single gain, Speex uses an integer to encode the pitch period, but
|
|
uses a 3-tap predictor (3 gains).
|
|
The adaptive codebook contribution
|
|
\begin_inset Formula $e_{a}[n]$
|
|
\end_inset
|
|
|
|
can thus be expressed as:
|
|
\begin_inset Formula \begin{equation}
|
|
e_{a}[n]=g_{0}e[n-T-1]+g_{1}e[n-T]+g_{2}e[n-T+1]\label{eq:adaptive-3tap}\end{equation}
|
|
|
|
\end_inset
|
|
|
|
where
|
|
\begin_inset Formula $g_{0}$
|
|
\end_inset
|
|
|
|
,
|
|
\begin_inset Formula $g_{1}$
|
|
\end_inset
|
|
|
|
and
|
|
\begin_inset Formula $g_{2}$
|
|
\end_inset
|
|
|
|
are the jointly quantized pitch gains and
|
|
\begin_inset Formula $e[n]$
|
|
\end_inset
|
|
|
|
is the codec excitation memory.
|
|
It is worth noting that when the pitch is smaller than the sub-frame size,
|
|
we repeat the excitation at a period
|
|
\begin_inset Formula $T$
|
|
\end_inset
|
|
|
|
.
|
|
For example, when
|
|
\begin_inset Formula $n-T+1\geq0$
|
|
\end_inset
|
|
|
|
, we use
|
|
\begin_inset Formula $n-2T+1$
|
|
\end_inset
|
|
|
|
instead.
|
|
In most modes, the pitch period is encoded with 7 bits in the
|
|
\begin_inset Formula $\left[17,144\right]$
|
|
\end_inset
|
|
|
|
range and the
|
|
\begin_inset Formula $\beta_{i}$
|
|
\end_inset
|
|
|
|
coefficients are vector-quantized using 7 bits at higher bit-rates (15
|
|
kbps narrowband and above) and 5 bits at lower bit-rates (11 kbps narrowband
|
|
and below).
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Many current CELP codecs use moving average (MA) prediction to encode the
|
|
fixed codebook gain.
|
|
This provides slightly better coding at the expense of introducing a dependency
|
|
on previously encoded frames.
|
|
A second difference is that Speex encodes the fixed codebook gain as the
|
|
product of the global excitation gain
|
|
\begin_inset Formula $g_{frame}$
|
|
\end_inset
|
|
|
|
with a sub-frame gain corrections
|
|
\begin_inset Formula $g_{subf}$
|
|
\end_inset
|
|
|
|
.
|
|
This increases robustness to packet loss by eliminating the inter-frame
|
|
dependency.
|
|
The sub-frame gain correction is encoded before the fixed codebook is searched
|
|
(not closed-loop optimized) and uses between 0 and 3 bits per sub-frame,
|
|
depending on the bit-rate.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The third difference is that Speex uses sub-vector quantization of the innovatio
|
|
n (fixed codebook) signal instead of an algebraic codebook.
|
|
Each sub-frame is divided into sub-vectors of lengths ranging between 5
|
|
and 20 samples.
|
|
Each sub-vector is chosen from a bitrate-dependent codebook and all sub-vectors
|
|
are concatenated to form a sub-frame.
|
|
As an example, the 3.95 kbps mode uses a sub-vector size of 20 samples with
|
|
32 entries in the codebook (5 bits).
|
|
This means that the innovation is encoded with 10 bits per sub-frame, or
|
|
2000 bps.
|
|
On the other hand, the 18.2 kbps mode uses a sub-vector size of 5 samples
|
|
with 256 entries in the codebook (8 bits), so the innovation uses 64 bits
|
|
per sub-frame, or 12800 bps.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Bit-rates
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
So far, no MOS (Mean Opinion Score
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
mean opinion score
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
) subjective evaluation has been performed for Speex.
|
|
In order to give an idea of the quality achievable with it, table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:quality_vs_bps"
|
|
|
|
\end_inset
|
|
|
|
presents my own subjective opinion on it.
|
|
It should be noted that different people will perceive the quality differently
|
|
and that the person that designed the codec often has a bias (one way or
|
|
another) when it comes to subjective evaluation.
|
|
Last thing, it should be noted that for most codecs (including Speex) encoding
|
|
quality sometimes varies depending on the input.
|
|
Note that the complexity is only approximate (within 0.5 mflops and using
|
|
the lowest complexity setting).
|
|
Decoding requires approximately 0.5 mflops
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
complexity
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
in most modes (1 mflops with perceptual enhancement).
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float table
|
|
placement h
|
|
wide true
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="17" columns="5">
|
|
<features>
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Mode
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Quality
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Bit-rate
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
bit-rate
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(bps)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
mflops
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
complexity
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Quality/description
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
250
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
No transmission (DTX)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
2,150
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
6
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Vocoder (mostly for comfort noise)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
2
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
2
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5,950
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
9
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Very noticeable artifacts/noise, good intelligibility
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3-4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
8,000
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
10
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Artifacts/noise sometimes noticeable
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5-6
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
11,000
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
14
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Artifacts usually noticeable only with headphones
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7-8
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
15,000
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
11
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Need good headphones to tell the difference
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
6
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
9
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
18,200
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
17.5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Hard to tell the difference even with good headphones
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
10
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
24,600
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
14.5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Completely transparent for voice, good quality music
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
8
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3,950
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
10.5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Very noticeable artifacts/noise, good intelligibility
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
9
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
reserved
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
10
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
reserved
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
11
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
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\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
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\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
reserved
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
12
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
reserved
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
13
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Application-defined, interpreted by callback or skipped
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
14
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Speex in-band signaling
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
15
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
-
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Terminator code
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
end{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
Quality versus bit-rate
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "cap:quality_vs_bps"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Perceptual enhancement
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
perceptual enhancement
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
|
|
\series bold
|
|
This section was only valid for version 1.1.12 and earlier.
|
|
It does not apply to version 1.2-beta1 (and later), for which the new perceptual
|
|
enhancement is not yet documented.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This part of the codec only applies to the decoder and can even be changed
|
|
without affecting inter-operability.
|
|
For that reason, the implementation provided and described here should
|
|
only be considered as a reference implementation.
|
|
The enhancement system is divided into two parts.
|
|
First, the synthesis filter
|
|
\begin_inset Formula $S(z)=1/A(z)$
|
|
\end_inset
|
|
|
|
is replaced by an enhanced filter:
|
|
\begin_inset Formula \[
|
|
S'(z)=\frac{A\left(z/a_{2}\right)A\left(z/a_{3}\right)}{A\left(z\right)A\left(z/a_{1}\right)}\]
|
|
|
|
\end_inset
|
|
|
|
where
|
|
\begin_inset Formula $a_{1}$
|
|
\end_inset
|
|
|
|
and
|
|
\begin_inset Formula $a_{2}$
|
|
\end_inset
|
|
|
|
depend on the mode in use and
|
|
\begin_inset Formula $a_{3}=\frac{1}{r}\left(1-\frac{1-ra_{1}}{1-ra_{2}}\right)$
|
|
\end_inset
|
|
|
|
with
|
|
\begin_inset Formula $r=.9$
|
|
\end_inset
|
|
|
|
.
|
|
The second part of the enhancement consists of using a comb filter to enhance
|
|
the pitch in the excitation domain.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
Speex wideband mode (sub-band CELP)
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
wideband
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:Speex-wideband-mode"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For wideband, the Speex approach uses a
|
|
\emph on
|
|
q
|
|
\emph default
|
|
uadrature
|
|
\emph on
|
|
m
|
|
\emph default
|
|
irror
|
|
\emph on
|
|
f
|
|
\emph default
|
|
ilter
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
quadrature mirror filter
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(QMF) to split the band in two.
|
|
The 16 kHz signal is thus divided into two 8 kHz signals, one representing
|
|
the low band (0-4 kHz), the other the high band (4-8 kHz).
|
|
The low band is encoded with the narrowband mode described in section
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "sec:Speex-narrowband-mode"
|
|
|
|
\end_inset
|
|
|
|
in such a way that the resulting
|
|
\begin_inset Quotes eld
|
|
\end_inset
|
|
|
|
embedded narrowband bit-stream
|
|
\begin_inset Quotes erd
|
|
\end_inset
|
|
|
|
can also be decoded with the narrowband decoder.
|
|
Since the low band encoding has already been described, only the high band
|
|
encoding is described in this section.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Linear Prediction
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The linear prediction part used for the high-band is very similar to what
|
|
is done for narrowband.
|
|
The only difference is that we use only 12 bits to encode the high-band
|
|
LSP's using a multi-stage vector quantizer (MSVQ).
|
|
The first level quantizes the 10 coefficients with 6 bits and the error
|
|
is then quantized using 6 bits, too.
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Pitch Prediction
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
That part is easy: there's no pitch prediction for the high-band.
|
|
There are two reasons for that.
|
|
First, there is usually little harmonic structure in this band (above 4
|
|
kHz).
|
|
Second, it would be very hard to implement since the QMF folds the 4-8
|
|
kHz band into 4-0 kHz (reversing the frequency axis), which means that
|
|
the location of the harmonics is no longer at multiples of the fundamental
|
|
(pitch).
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Excitation Quantization
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The high-band excitation is coded in the same way as for narrowband.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
Bit allocation
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
For the wideband mode, the entire narrowband frame is packed before the
|
|
high-band is encoded.
|
|
The narrowband part of the bit-stream is as defined in table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:bits-narrowband"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
The high-band follows, as described in table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "cap:bits-wideband"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
For wideband, the mode ID is the same as the Speex quality setting and
|
|
is defined in table
|
|
\begin_inset CommandInset ref
|
|
LatexCommand ref
|
|
reference "tab:wideband-quality"
|
|
|
|
\end_inset
|
|
|
|
.
|
|
This also means that a wideband frame may be correctly decoded by a narrowband
|
|
decoder with the only caveat that if more than one frame is packed in the
|
|
same packet, the decoder will need to skip the high-band parts in order
|
|
to sync with the bit-stream.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float table
|
|
placement h
|
|
wide true
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="7" columns="7">
|
|
<features>
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Parameter
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Update rate
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
2
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Wideband bit
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Mode ID
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
LSP
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
12
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
12
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
12
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
12
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Excitation gain
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
sub-frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Excitation VQ
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
sub-frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
20
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
40
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
80
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Total
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
frame
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
36
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
112
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
192
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
352
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
end{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
Bit allocation for high-band in wideband mode
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "cap:bits-wideband"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Float table
|
|
placement h
|
|
wide true
|
|
sideways false
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
begin{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset Tabular
|
|
<lyxtabular version="3" rows="12" columns="3">
|
|
<features>
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<column alignment="center" valignment="top" width="0pt">
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Mode/Quality
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Bit-rate
|
|
\begin_inset Index
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
bit-rate
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
(bps)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Quality/description
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
0
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3,950
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Barely intelligible (mostly for comfort noise)
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
1
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5,750
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Very noticeable artifacts/noise, poor intelligibility
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
2
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7,750
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Very noticeable artifacts/noise, good intelligibility
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
3
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
9,800
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Artifacts/noise sometimes annoying
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
4
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
12,800
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Artifacts/noise usually noticeable
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
5
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
16,800
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Artifacts/noise sometimes noticeable
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
6
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
20,600
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Need good headphones to tell the difference
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
7
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
23,800
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Need good headphones to tell the difference
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
8
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
27,800
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Hard to tell the difference even with good headphones
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
9
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
34,200
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Hard to tell the difference even with good headphones
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
<row>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
10
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
42,200
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
<cell alignment="center" valignment="top" topline="true" bottomline="true" leftline="true" rightline="true" usebox="none">
|
|
\begin_inset Text
|
|
|
|
\begin_layout Plain Layout
|
|
Completely transparent for voice, good quality music
|
|
\end_layout
|
|
|
|
\end_inset
|
|
</cell>
|
|
</row>
|
|
</lyxtabular>
|
|
|
|
\end_inset
|
|
|
|
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
end{center}
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Plain Layout
|
|
\begin_inset Caption
|
|
|
|
\begin_layout Plain Layout
|
|
Quality versus bit-rate for the wideband encoder
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "tab:wideband-quality"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset ERT
|
|
status open
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
clearpage
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset ERT
|
|
status collapsed
|
|
|
|
\begin_layout Plain Layout
|
|
|
|
|
|
\backslash
|
|
clearpage
|
|
\end_layout
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
\start_of_appendix
|
|
Sample code
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:Sample-code"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This section shows sample code for encoding and decoding speech using the
|
|
Speex API.
|
|
The commands can be used to encode and decode a file by calling:
|
|
\family typewriter
|
|
|
|
\begin_inset Newline newline
|
|
\end_inset
|
|
|
|
% sampleenc in_file.sw | sampledec out_file.sw
|
|
\family default
|
|
|
|
\begin_inset Newline newline
|
|
\end_inset
|
|
|
|
where both files are raw (no header) files encoded at 16 bits per sample
|
|
(in the machine natural endianness).
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
sampleenc.c
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
sampleenc takes a raw 16 bits/sample file, encodes it and outputs a Speex
|
|
stream to stdout.
|
|
Note that the packing used is
|
|
\series bold
|
|
not
|
|
\series default
|
|
compatible with that of speexenc/speexdec.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "sampleenc.c"
|
|
lstparams "caption={Source code for sampleenc},label={sampleenc-source-code},numbers=left,numberstyle={\\footnotesize}"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section
|
|
sampledec.c
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
sampledec reads a Speex stream from stdin, decodes it and outputs it to
|
|
a raw 16 bits/sample file.
|
|
Note that the packing used is
|
|
\series bold
|
|
not
|
|
\series default
|
|
compatible with that of speexenc/speexdec.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "sampledec.c"
|
|
lstparams "caption={Source code for sampledec},label={sampledec-source-code},numbers=left,numberstyle={\\footnotesize}"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
Jitter Buffer for Speex
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand lstinputlisting
|
|
filename "../speexclient/speex_jitter_buffer.c"
|
|
lstparams "caption={Example of using the jitter buffer for Speex packets},label={example-speex-jitter},numbers=left,numberstyle={\\footnotesize}"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
IETF RTP Profile
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:IETF-draft"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand verbatiminput
|
|
filename "draft-ietf-avt-rtp-speex-05-tmp.txt"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
Speex License
|
|
\begin_inset CommandInset label
|
|
LatexCommand label
|
|
name "sec:Speex-License"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset include
|
|
LatexCommand verbatiminput
|
|
filename "../COPYING"
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset Newpage newpage
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Chapter
|
|
GNU Free Documentation License
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Version 1.1, March 2000
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Copyright (C) 2000 Free Software Foundation, Inc.
|
|
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Everyone is permitted
|
|
to copy and distribute verbatim copies of this license document, but changing
|
|
it is not allowed.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
0.
|
|
PREAMBLE
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The purpose of this License is to make a manual, textbook, or other written
|
|
document "free" in the sense of freedom: to assure everyone the effective
|
|
freedom to copy and redistribute it, with or without modifying it, either
|
|
commercially or noncommercially.
|
|
Secondarily, this License preserves for the author and publisher a way
|
|
to get credit for their work, while not being considered responsible for
|
|
modifications made by others.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This License is a kind of "copyleft", which means that derivative works
|
|
of the document must themselves be free in the same sense.
|
|
It complements the GNU General Public License, which is a copyleft license
|
|
designed for free software.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
We have designed this License in order to use it for manuals for free software,
|
|
because free software needs free documentation: a free program should come
|
|
with manuals providing the same freedoms that the software does.
|
|
But this License is not limited to software manuals; it can be used for
|
|
any textual work, regardless of subject matter or whether it is published
|
|
as a printed book.
|
|
We recommend this License principally for works whose purpose is instruction
|
|
or reference.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
1.
|
|
APPLICABILITY AND DEFINITIONS
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
This License applies to any manual or other work that contains a notice
|
|
placed by the copyright holder saying it can be distributed under the terms
|
|
of this License.
|
|
The "Document", below, refers to any such manual or work.
|
|
Any member of the public is a licensee, and is addressed as "you".
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
A "Modified Version" of the Document means any work containing the Document
|
|
or a portion of it, either copied verbatim, or with modifications and/or
|
|
translated into another language.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
A "Secondary Section" is a named appendix or a front-matter section of the
|
|
Document that deals exclusively with the relationship of the publishers
|
|
or authors of the Document to the Document's overall subject (or to related
|
|
matters) and contains nothing that could fall directly within that overall
|
|
subject.
|
|
(For example, if the Document is in part a textbook of mathematics, a Secondary
|
|
Section may not explain any mathematics.) The relationship could be a matter
|
|
of historical connection with the subject or with related matters, or of
|
|
legal, commercial, philosophical, ethical or political position regarding
|
|
them.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The "Invariant Sections" are certain Secondary Sections whose titles are
|
|
designated, as being those of Invariant Sections, in the notice that says
|
|
that the Document is released under this License.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The "Cover Texts" are certain short passages of text that are listed, as
|
|
Front-Cover Texts or Back-Cover Texts, in the notice that says that the
|
|
Document is released under this License.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
A "Transparent" copy of the Document means a machine-readable copy, represented
|
|
in a format whose specification is available to the general public, whose
|
|
contents can be viewed and edited directly and straightforwardly with generic
|
|
text editors or (for images composed of pixels) generic paint programs
|
|
or (for drawings) some widely available drawing editor, and that is suitable
|
|
for input to text formatters or for automatic translation to a variety
|
|
of formats suitable for input to text formatters.
|
|
A copy made in an otherwise Transparent file format whose markup has been
|
|
designed to thwart or discourage subsequent modification by readers is
|
|
not Transparent.
|
|
A copy that is not "Transparent" is called "Opaque".
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Examples of suitable formats for Transparent copies include plain ASCII
|
|
without markup, Texinfo input format, LaTeX input format, SGML or XML using
|
|
a publicly available DTD, and standard-conforming simple HTML designed
|
|
for human modification.
|
|
Opaque formats include PostScript, PDF, proprietary formats that can be
|
|
read and edited only by proprietary word processors, SGML or XML for which
|
|
the DTD and/or processing tools are not generally available, and the machine-ge
|
|
nerated HTML produced by some word processors for output purposes only.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The "Title Page" means, for a printed book, the title page itself, plus
|
|
such following pages as are needed to hold, legibly, the material this
|
|
License requires to appear in the title page.
|
|
For works in formats which do not have any title page as such, "Title Page"
|
|
means the text near the most prominent appearance of the work's title,
|
|
preceding the beginning of the body of the text.
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
2.
|
|
VERBATIM COPYING
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
You may copy and distribute the Document in any medium, either commercially
|
|
or noncommercially, provided that this License, the copyright notices,
|
|
and the license notice saying this License applies to the Document are
|
|
reproduced in all copies, and that you add no other conditions whatsoever
|
|
to those of this License.
|
|
You may not use technical measures to obstruct or control the reading or
|
|
further copying of the copies you make or distribute.
|
|
However, you may accept compensation in exchange for copies.
|
|
If you distribute a large enough number of copies you must also follow
|
|
the conditions in section 3.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
You may also lend copies, under the same conditions stated above, and you
|
|
may publicly display copies.
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
3.
|
|
COPYING IN QUANTITY
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
If you publish printed copies of the Document numbering more than 100, and
|
|
the Document's license notice requires Cover Texts, you must enclose the
|
|
copies in covers that carry, clearly and legibly, all these Cover Texts:
|
|
Front-Cover Texts on the front cover, and Back-Cover Texts on the back
|
|
cover.
|
|
Both covers must also clearly and legibly identify you as the publisher
|
|
of these copies.
|
|
The front cover must present the full title with all words of the title
|
|
equally prominent and visible.
|
|
You may add other material on the covers in addition.
|
|
Copying with changes limited to the covers, as long as they preserve the
|
|
title of the Document and satisfy these conditions, can be treated as verbatim
|
|
copying in other respects.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
If the required texts for either cover are too voluminous to fit legibly,
|
|
you should put the first ones listed (as many as fit reasonably) on the
|
|
actual cover, and continue the rest onto adjacent pages.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
If you publish or distribute Opaque copies of the Document numbering more
|
|
than 100, you must either include a machine-readable Transparent copy along
|
|
with each Opaque copy, or state in or with each Opaque copy a publicly-accessib
|
|
le computer-network location containing a complete Transparent copy of the
|
|
Document, free of added material, which the general network-using public
|
|
has access to download anonymously at no charge using public-standard network
|
|
protocols.
|
|
If you use the latter option, you must take reasonably prudent steps, when
|
|
you begin distribution of Opaque copies in quantity, to ensure that this
|
|
Transparent copy will remain thus accessible at the stated location until
|
|
at least one year after the last time you distribute an Opaque copy (directly
|
|
or through your agents or retailers) of that edition to the public.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
It is requested, but not required, that you contact the authors of the Document
|
|
well before redistributing any large number of copies, to give them a chance
|
|
to provide you with an updated version of the Document.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
4.
|
|
MODIFICATIONS
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
You may copy and distribute a Modified Version of the Document under the
|
|
conditions of sections 2 and 3 above, provided that you release the Modified
|
|
Version under precisely this License, with the Modified Version filling
|
|
the role of the Document, thus licensing distribution and modification
|
|
of the Modified Version to whoever possesses a copy of it.
|
|
In addition, you must do these things in the Modified Version:
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
A.
|
|
Use in the Title Page (and on the covers, if any) a title distinct from
|
|
that of the Document, and from those of previous versions (which should,
|
|
if there were any, be listed in the History section of the Document).
|
|
You may use the same title as a previous version if the original publisher
|
|
of that version gives permission.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
B.
|
|
List on the Title Page, as authors, one or more persons or entities responsible
|
|
for authorship of the modifications in the Modified Version, together with
|
|
at least five of the principal authors of the Document (all of its principal
|
|
authors, if it has less than five).
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
C.
|
|
State on the Title page the name of the publisher of the Modified Version,
|
|
as the publisher.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
D.
|
|
Preserve all the copyright notices of the Document.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
E.
|
|
Add an appropriate copyright notice for your modifications adjacent to
|
|
the other copyright notices.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
F.
|
|
Include, immediately after the copyright notices, a license notice giving
|
|
the public permission to use the Modified Version under the terms of this
|
|
License, in the form shown in the Addendum below.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
G.
|
|
Preserve in that license notice the full lists of Invariant Sections and
|
|
required Cover Texts given in the Document's license notice.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
H.
|
|
Include an unaltered copy of this License.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
I.
|
|
Preserve the section entitled "History", and its title, and add to it an
|
|
item stating at least the title, year, new authors, and publisher of the
|
|
Modified Version as given on the Title Page.
|
|
If there is no section entitled "History" in the Document, create one stating
|
|
the title, year, authors, and publisher of the Document as given on its
|
|
Title Page, then add an item describing the Modified Version as stated
|
|
in the previous sentence.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
J.
|
|
Preserve the network location, if any, given in the Document for public
|
|
access to a Transparent copy of the Document, and likewise the network
|
|
locations given in the Document for previous versions it was based on.
|
|
These may be placed in the "History" section.
|
|
You may omit a network location for a work that was published at least
|
|
four years before the Document itself, or if the original publisher of
|
|
the version it refers to gives permission.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
K.
|
|
In any section entitled "Acknowledgements" or "Dedications", preserve the
|
|
section's title, and preserve in the section all the substance and tone
|
|
of each of the contributor acknowledgements and/or dedications given therein.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
L.
|
|
Preserve all the Invariant Sections of the Document, unaltered in their
|
|
text and in their titles.
|
|
Section numbers or the equivalent are not considered part of the section
|
|
titles.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
M.
|
|
Delete any section entitled "Endorsements".
|
|
Such a section may not be included in the Modified Version.
|
|
\end_layout
|
|
|
|
\begin_layout Itemize
|
|
N.
|
|
Do not retitle any existing section as "Endorsements" or to conflict in
|
|
title with any Invariant Section.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
If the Modified Version includes new front-matter sections or appendices
|
|
that qualify as Secondary Sections and contain no material copied from
|
|
the Document, you may at your option designate some or all of these sections
|
|
as invariant.
|
|
To do this, add their titles to the list of Invariant Sections in the Modified
|
|
Version's license notice.
|
|
These titles must be distinct from any other section titles.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
You may add a section entitled "Endorsements", provided it contains nothing
|
|
but endorsements of your Modified Version by various parties--for example,
|
|
statements of peer review or that the text has been approved by an organization
|
|
as the authoritative definition of a standard.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
You may add a passage of up to five words as a Front-Cover Text, and a passage
|
|
of up to 25 words as a Back-Cover Text, to the end of the list of Cover
|
|
Texts in the Modified Version.
|
|
Only one passage of Front-Cover Text and one of Back-Cover Text may be
|
|
added by (or through arrangements made by) any one entity.
|
|
If the Document already includes a cover text for the same cover, previously
|
|
added by you or by arrangement made by the same entity you are acting on
|
|
behalf of, you may not add another; but you may replace the old one, on
|
|
explicit permission from the previous publisher that added the old one.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The author(s) and publisher(s) of the Document do not by this License give
|
|
permission to use their names for publicity for or to assert or imply endorseme
|
|
nt of any Modified Version.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
5.
|
|
COMBINING DOCUMENTS
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
You may combine the Document with other documents released under this License,
|
|
under the terms defined in section 4 above for modified versions, provided
|
|
that you include in the combination all of the Invariant Sections of all
|
|
of the original documents, unmodified, and list them all as Invariant Sections
|
|
of your combined work in its license notice.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The combined work need only contain one copy of this License, and multiple
|
|
identical Invariant Sections may be replaced with a single copy.
|
|
If there are multiple Invariant Sections with the same name but different
|
|
contents, make the title of each such section unique by adding at the end
|
|
of it, in parentheses, the name of the original author or publisher of
|
|
that section if known, or else a unique number.
|
|
Make the same adjustment to the section titles in the list of Invariant
|
|
Sections in the license notice of the combined work.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
In the combination, you must combine any sections entitled "History" in
|
|
the various original documents, forming one section entitled "History";
|
|
likewise combine any sections entitled "Acknowledgements", and any sections
|
|
entitled "Dedications".
|
|
You must delete all sections entitled "Endorsements."
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
6.
|
|
COLLECTIONS OF DOCUMENTS
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
You may make a collection consisting of the Document and other documents
|
|
released under this License, and replace the individual copies of this
|
|
License in the various documents with a single copy that is included in
|
|
the collection, provided that you follow the rules of this License for
|
|
verbatim copying of each of the documents in all other respects.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
You may extract a single document from such a collection, and distribute
|
|
it individually under this License, provided you insert a copy of this
|
|
License into the extracted document, and follow this License in all other
|
|
respects regarding verbatim copying of that document.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
7.
|
|
AGGREGATION WITH INDEPENDENT WORKS
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
A compilation of the Document or its derivatives with other separate and
|
|
independent documents or works, in or on a volume of a storage or distribution
|
|
medium, does not as a whole count as a Modified Version of the Document,
|
|
provided no compilation copyright is claimed for the compilation.
|
|
Such a compilation is called an "aggregate", and this License does not
|
|
apply to the other self-contained works thus compiled with the Document,
|
|
on account of their being thus compiled, if they are not themselves derivative
|
|
works of the Document.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
If the Cover Text requirement of section 3 is applicable to these copies
|
|
of the Document, then if the Document is less than one quarter of the entire
|
|
aggregate, the Document's Cover Texts may be placed on covers that surround
|
|
only the Document within the aggregate.
|
|
Otherwise they must appear on covers around the whole aggregate.
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
8.
|
|
TRANSLATION
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Translation is considered a kind of modification, so you may distribute
|
|
translations of the Document under the terms of section 4.
|
|
Replacing Invariant Sections with translations requires special permission
|
|
from their copyright holders, but you may include translations of some
|
|
or all Invariant Sections in addition to the original versions of these
|
|
Invariant Sections.
|
|
You may include a translation of this License provided that you also include
|
|
the original English version of this License.
|
|
In case of a disagreement between the translation and the original English
|
|
version of this License, the original English version will prevail.
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
9.
|
|
TERMINATION
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
You may not copy, modify, sublicense, or distribute the Document except
|
|
as expressly provided for under this License.
|
|
Any other attempt to copy, modify, sublicense or distribute the Document
|
|
is void, and will automatically terminate your rights under this License.
|
|
However, parties who have received copies, or rights, from you under this
|
|
License will not have their licenses terminated so long as such parties
|
|
remain in full compliance.
|
|
|
|
\end_layout
|
|
|
|
\begin_layout Section*
|
|
10.
|
|
FUTURE REVISIONS OF THIS LICENSE
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
The Free Software Foundation may publish new, revised versions of the GNU
|
|
Free Documentation License from time to time.
|
|
Such new versions will be similar in spirit to the present version, but
|
|
may differ in detail to address new problems or concerns.
|
|
See http://www.gnu.org/copyleft/.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
Each version of the License is given a distinguishing version number.
|
|
If the Document specifies that a particular numbered version of this License
|
|
"or any later version" applies to it, you have the option of following
|
|
the terms and conditions either of that specified version or of any later
|
|
version that has been published (not as a draft) by the Free Software Foundatio
|
|
n.
|
|
If the Document does not specify a version number of this License, you
|
|
may choose any version ever published (not as a draft) by the Free Software
|
|
Foundation.
|
|
\end_layout
|
|
|
|
\begin_layout Standard
|
|
\begin_inset CommandInset index_print
|
|
LatexCommand printindex
|
|
|
|
\end_inset
|
|
|
|
|
|
\end_layout
|
|
|
|
\end_body
|
|
\end_document
|