75 lines
3.7 KiB
C
75 lines
3.7 KiB
C
/***********************************************************************
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Copyright (c) 2006-2011, Skype Limited. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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- Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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- Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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- Neither the name of Internet Society, IETF or IETF Trust, nor the
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names of specific contributors, may be used to endorse or promote
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products derived from this software without specific prior written
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permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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***********************************************************************/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "SigProc_FIX.h"
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/* Coefficients for 2-band filter bank based on first-order allpass filters */
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static opus_int16 A_fb1_20 = 5394 << 1;
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static opus_int16 A_fb1_21 = -24290; /* (opus_int16)(20623 << 1) */
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/* Split signal into two decimated bands using first-order allpass filters */
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void silk_ana_filt_bank_1(
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const opus_int16 *in, /* I Input signal [N] */
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opus_int32 *S, /* I/O State vector [2] */
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opus_int16 *outL, /* O Low band [N/2] */
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opus_int16 *outH, /* O High band [N/2] */
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const opus_int32 N /* I Number of input samples */
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)
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{
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opus_int k, N2 = silk_RSHIFT( N, 1 );
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opus_int32 in32, X, Y, out_1, out_2;
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/* Internal variables and state are in Q10 format */
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for( k = 0; k < N2; k++ ) {
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/* Convert to Q10 */
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in32 = silk_LSHIFT( (opus_int32)in[ 2 * k ], 10 );
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/* All-pass section for even input sample */
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Y = silk_SUB32( in32, S[ 0 ] );
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X = silk_SMLAWB( Y, Y, A_fb1_21 );
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out_1 = silk_ADD32( S[ 0 ], X );
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S[ 0 ] = silk_ADD32( in32, X );
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/* Convert to Q10 */
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in32 = silk_LSHIFT( (opus_int32)in[ 2 * k + 1 ], 10 );
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/* All-pass section for odd input sample, and add to output of previous section */
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Y = silk_SUB32( in32, S[ 1 ] );
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X = silk_SMULWB( Y, A_fb1_20 );
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out_2 = silk_ADD32( S[ 1 ], X );
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S[ 1 ] = silk_ADD32( in32, X );
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/* Add/subtract, convert back to int16 and store to output */
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outL[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( silk_ADD32( out_2, out_1 ), 11 ) );
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outH[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( silk_SUB32( out_2, out_1 ), 11 ) );
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}
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}
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