74 lines
3.4 KiB
C
74 lines
3.4 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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#include "resampler_rom.h"
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/* Downsample by a factor 2 */
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void silk_resampler_down2(
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opus_int32 *S, /* I/O State vector [ 2 ] */
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opus_int16 *out, /* O Output signal [ floor(len/2) ] */
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const opus_int16 *in, /* I Input signal [ len ] */
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opus_int32 inLen /* I Number of input samples */
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)
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{
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opus_int32 k, len2 = silk_RSHIFT32( inLen, 1 );
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opus_int32 in32, out32, Y, X;
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celt_assert( silk_resampler_down2_0 > 0 );
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celt_assert( silk_resampler_down2_1 < 0 );
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/* Internal variables and state are in Q10 format */
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for( k = 0; k < len2; 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, silk_resampler_down2_1 );
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out32 = 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, silk_resampler_down2_0 );
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out32 = silk_ADD32( out32, S[ 1 ] );
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out32 = silk_ADD32( out32, X );
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S[ 1 ] = silk_ADD32( in32, X );
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/* Add, convert back to int16 and store to output */
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out[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( out32, 11 ) );
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}
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}
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