WSJT-X/portaudio-v19/docs/pa_tut_open.html
Diane Bruce 5b9645bf09 - Import of portaudio v19
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<meta name="Description" content="Tutorial for PortAudio, a cross platform, open-source, audio I/O library.It provides a very simple API for recording and/or playing sound using a simple callback function.">
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<h1>
PortAudio Tutorial</h1></center>
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<h2>
Opening a Stream using Defaults</h2>
<blockquote>The next step is to open a stream which is similar to opening
a file. You can specify whether you want audio input and/or output, how
many channels, the data format, sample rate, etc. There are two calls for
opening streams, <tt>Pa_OpenStream</tt>() and <tt>Pa_OpenDefaultStream</tt>().
<p><tt>Pa_OpenStream()</tt> takes extra&nbsp; parameters which give you
more control. You can normally just use <tt>Pa_OpenDefaultStream</tt>()
which just calls <tt>Pa_OpenStream()</tt> <tt>with</tt> some reasonable
default values.&nbsp; Let's open a stream for stereo output, using floating
point data, at 44100 Hz.
<blockquote>
<pre>err = Pa_OpenDefaultStream(
&nbsp;&nbsp;&nbsp; &amp;stream,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /* passes back stream pointer */
&nbsp;&nbsp;&nbsp; 0,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /* no input channels */
&nbsp;&nbsp;&nbsp; 2,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /* stereo output */
&nbsp;&nbsp;&nbsp; paFloat32,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /* 32 bit floating point output */
&nbsp;&nbsp;&nbsp; 44100,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /* sample rate */
&nbsp;&nbsp;&nbsp; 256,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /* frames per buffer */
&nbsp;&nbsp;&nbsp; 0,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /* number of buffers, if zero then use default minimum */
&nbsp;&nbsp;&nbsp; patestCallback, /* specify our custom callback */
&nbsp;&nbsp;&nbsp; &amp;data );&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /* pass our data through to callback */</pre>
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If you want to use 16 bit integer data, pass <tt>paInt16</tt> instead of
<tt>paFloat32</tt>.</blockquote>
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