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- /***********************************************************************
- Copyright (c) 2006-2011, Skype Limited. All rights reserved.
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions
- are met:
- - Redistributions of source code must retain the above copyright notice,
- this list of conditions and the following disclaimer.
- - Redistributions in binary form must reproduce the above copyright
- notice, this list of conditions and the following disclaimer in the
- documentation and/or other materials provided with the distribution.
- - Neither the name of Internet Society, IETF or IETF Trust, nor the
- names of specific contributors, may be used to endorse or promote
- products derived from this software without specific prior written
- permission.
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- POSSIBILITY OF SUCH DAMAGE.
- ***********************************************************************/
- #ifdef HAVE_CONFIG_H
- #include "config.h"
- #endif
- #include "SigProc_FIX.h"
- #include "resampler_rom.h"
- /* Downsample by a factor 2 */
- void silk_resampler_down2(
- opus_int32 *S, /* I/O State vector [ 2 ] */
- opus_int16 *out, /* O Output signal [ floor(len/2) ] */
- const opus_int16 *in, /* I Input signal [ len ] */
- opus_int32 inLen /* I Number of input samples */
- )
- {
- opus_int32 k, len2 = silk_RSHIFT32( inLen, 1 );
- opus_int32 in32, out32, Y, X;
- celt_assert( silk_resampler_down2_0 > 0 );
- celt_assert( silk_resampler_down2_1 < 0 );
- /* Internal variables and state are in Q10 format */
- for( k = 0; k < len2; k++ ) {
- /* Convert to Q10 */
- in32 = silk_LSHIFT( (opus_int32)in[ 2 * k ], 10 );
- /* All-pass section for even input sample */
- Y = silk_SUB32( in32, S[ 0 ] );
- X = silk_SMLAWB( Y, Y, silk_resampler_down2_1 );
- out32 = silk_ADD32( S[ 0 ], X );
- S[ 0 ] = silk_ADD32( in32, X );
- /* Convert to Q10 */
- in32 = silk_LSHIFT( (opus_int32)in[ 2 * k + 1 ], 10 );
- /* All-pass section for odd input sample, and add to output of previous section */
- Y = silk_SUB32( in32, S[ 1 ] );
- X = silk_SMULWB( Y, silk_resampler_down2_0 );
- out32 = silk_ADD32( out32, S[ 1 ] );
- out32 = silk_ADD32( out32, X );
- S[ 1 ] = silk_ADD32( in32, X );
- /* Add, convert back to int16 and store to output */
- out[ k ] = (opus_int16)silk_SAT16( silk_RSHIFT_ROUND( out32, 11 ) );
- }
- }
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