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61 lines
2.7 KiB
C
61 lines
2.7 KiB
C
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/***********************************************************************
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Copyright (c) 2006-2010, 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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#include "SKP_Silk_SigProc_FIX.h"
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/* Chirp (bandwidth expand) LP AR filter */
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void SKP_Silk_bwexpander(
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SKP_int16 *ar, /* I/O AR filter to be expanded (without leading 1) */
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const SKP_int d, /* I Length of ar */
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SKP_int32 chirp_Q16 /* I Chirp factor (typically in the range 0 to 1) */
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)
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{
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SKP_int i;
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SKP_int32 chirp_minus_one_Q16;
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chirp_minus_one_Q16 = chirp_Q16 - 65536;
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/* NB: Dont use SKP_SMULWB, instead of SKP_RSHIFT_ROUND( SKP_MUL() , 16 ), below. */
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/* Bias in SKP_SMULWB can lead to unstable filters */
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for( i = 0; i < d - 1; i++ ) {
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ar[ i ] = (SKP_int16)SKP_RSHIFT_ROUND( SKP_MUL( chirp_Q16, ar[ i ] ), 16 );
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chirp_Q16 += SKP_RSHIFT_ROUND( SKP_MUL( chirp_Q16, chirp_minus_one_Q16 ), 16 );
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}
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ar[ d - 1 ] = (SKP_int16)SKP_RSHIFT_ROUND( SKP_MUL( chirp_Q16, ar[ d - 1 ] ), 16 );
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}
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