94 lines
4.5 KiB
C
94 lines
4.5 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, (subject to the limitations in the disclaimer below)
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are permitted provided that the following conditions 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 Skype Limited, nor the names of specific
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contributors, may be used to endorse or promote products derived from
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this software without specific prior written permission.
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NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED
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BY THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
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BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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***********************************************************************/
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/* *
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* SKP_Silk_resampler_down3.c *
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* *
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* Downsample by a factor 3, low quality *
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* *
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* Copyright 2010 (c), Skype Limited *
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* */
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#include "SKP_Silk_SigProc_FIX.h"
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#include "SKP_Silk_resampler_private.h"
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#define ORDER_FIR 6
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/* Downsample by a factor 3, low quality */
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void SKP_Silk_resampler_down3(
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SKP_int32 *S, /* I/O: State vector [ 8 ] */
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SKP_int16 *out, /* O: Output signal [ floor(inLen/3) ] */
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const SKP_int16 *in, /* I: Input signal [ inLen ] */
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SKP_int32 inLen /* I: Number of input samples */
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)
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{
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SKP_int32 nSamplesIn, counter, res_Q6;
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SKP_int32 buf[ RESAMPLER_MAX_BATCH_SIZE_IN + ORDER_FIR ];
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SKP_int32 *buf_ptr;
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/* Copy buffered samples to start of buffer */
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SKP_memcpy( buf, S, ORDER_FIR * sizeof( SKP_int32 ) );
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/* Iterate over blocks of frameSizeIn input samples */
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while( 1 ) {
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nSamplesIn = SKP_min( inLen, RESAMPLER_MAX_BATCH_SIZE_IN );
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/* Second-order AR filter (output in Q8) */
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SKP_Silk_resampler_private_AR2( &S[ ORDER_FIR ], &buf[ ORDER_FIR ], in,
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SKP_Silk_Resampler_1_3_COEFS_LQ, nSamplesIn );
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/* Interpolate filtered signal */
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buf_ptr = buf;
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counter = nSamplesIn;
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while( counter > 2 ) {
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/* Inner product */
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res_Q6 = SKP_SMULWB( SKP_ADD32( buf_ptr[ 0 ], buf_ptr[ 5 ] ), SKP_Silk_Resampler_1_3_COEFS_LQ[ 2 ] );
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res_Q6 = SKP_SMLAWB( res_Q6, SKP_ADD32( buf_ptr[ 1 ], buf_ptr[ 4 ] ), SKP_Silk_Resampler_1_3_COEFS_LQ[ 3 ] );
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res_Q6 = SKP_SMLAWB( res_Q6, SKP_ADD32( buf_ptr[ 2 ], buf_ptr[ 3 ] ), SKP_Silk_Resampler_1_3_COEFS_LQ[ 4 ] );
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/* Scale down, saturate and store in output array */
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*out++ = (SKP_int16)SKP_SAT16( SKP_RSHIFT_ROUND( res_Q6, 6 ) );
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buf_ptr += 3;
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counter -= 3;
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}
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in += nSamplesIn;
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inLen -= nSamplesIn;
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if( inLen > 0 ) {
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/* More iterations to do; copy last part of filtered signal to beginning of buffer */
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SKP_memcpy( buf, &buf[ nSamplesIn ], ORDER_FIR * sizeof( SKP_int32 ) );
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} else {
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break;
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}
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}
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/* Copy last part of filtered signal to the state for the next call */
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SKP_memcpy( S, &buf[ nSamplesIn ], ORDER_FIR * sizeof( SKP_int32 ) );
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}
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