78 lines
4.2 KiB
C
78 lines
4.2 KiB
C
/***********************************************************************
|
|
Copyright (c) 2006-2010, Skype Limited. All rights reserved.
|
|
Redistribution and use in source and binary forms, with or without
|
|
modification, (subject to the limitations in the disclaimer below)
|
|
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 Skype Limited, nor the names of specific
|
|
contributors, may be used to endorse or promote products derived from
|
|
this software without specific prior written permission.
|
|
NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED
|
|
BY THIS LICENSE. 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.
|
|
***********************************************************************/
|
|
|
|
/* *
|
|
* SKP_Silk_resample_1_2 *
|
|
* *
|
|
* Downsample by a factor 2 *
|
|
* *
|
|
* Copyright 2006 (c), Skype Limited *
|
|
* Date: 060221 *
|
|
* */
|
|
#include "SKP_Silk_SigProc_FIX.h"
|
|
|
|
/* Coefficients for 2-fold resampling */
|
|
static SKP_int16 A20_Resample_1_2[ 3 ] = { 1254, 10102, 22898 };
|
|
static SKP_int16 A21_Resample_1_2[ 3 ] = { 4810, 16371, 29374 };
|
|
|
|
|
|
/* Downsample by a factor 2 */
|
|
void SKP_Silk_resample_1_2(
|
|
const SKP_int16 *in, /* I: 16 kHz signal [2*len] */
|
|
SKP_int32 *S, /* I/O: State vector [6] */
|
|
SKP_int16 *out, /* O: 8 kHz signal [len] */
|
|
SKP_int32 *scratch, /* I: Scratch memory [4*len] */
|
|
const SKP_int32 len /* I: Number of OUTPUT samples*/
|
|
)
|
|
{
|
|
SKP_int32 k, idx;
|
|
|
|
/* De-interleave allpass inputs, and convert Q15 -> Q25 */
|
|
for( k = 0; k < len; k++ ) {
|
|
idx = SKP_LSHIFT( k, 1 );
|
|
scratch[ k ] = SKP_LSHIFT( (SKP_int32)in[ idx ], 10 );
|
|
scratch[ k + len ] = SKP_LSHIFT( (SKP_int32)in[ idx + 1 ], 10 );
|
|
}
|
|
|
|
idx = SKP_LSHIFT( len, 1 );
|
|
|
|
/* Allpass filters */
|
|
SKP_Silk_allpass_int( scratch, S, A21_Resample_1_2[ 0 ], scratch + idx, len );
|
|
SKP_Silk_allpass_int( scratch + idx, S + 1, A21_Resample_1_2[ 1 ], scratch + idx + len, len );
|
|
SKP_Silk_allpass_int( scratch + idx + len, S + 2, A21_Resample_1_2[ 2 ], scratch, len );
|
|
|
|
SKP_Silk_allpass_int( scratch + len, S + 3, A20_Resample_1_2[ 0 ], scratch + idx, len );
|
|
SKP_Silk_allpass_int( scratch + idx, S + 4, A20_Resample_1_2[ 1 ], scratch + idx + len, len );
|
|
SKP_Silk_allpass_int( scratch + idx + len, S + 5, A20_Resample_1_2[ 2 ], scratch + len, len );
|
|
|
|
/* Add two allpass outputs */
|
|
for( k = 0; k < len; k++ ) {
|
|
out[ k ] = (SKP_int16)SKP_SAT16( SKP_RSHIFT_ROUND( scratch[ k ] + scratch[ k + len ], 11 ) );
|
|
}
|
|
}
|
|
|