85 lines
4.1 KiB
C
Executable File
85 lines
4.1 KiB
C
Executable File
/***********************************************************************
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Copyright (c) 2006-2012, 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_LPC_synthesis_filter.c *
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* Coefficients are in Q12 *
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* *
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* even order AR filter *
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* */
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#include "SKP_Silk_SigProc_FIX.h"
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/* even order AR filter */
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void SKP_Silk_LPC_synthesis_filter(
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const SKP_int16 *in, /* I: excitation signal */
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const SKP_int16 *A_Q12, /* I: AR coefficients [Order], between -8_Q0 and 8_Q0 */
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const SKP_int32 Gain_Q26, /* I: gain */
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SKP_int32 *S, /* I/O: state vector [Order] */
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SKP_int16 *out, /* O: output signal */
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const SKP_int32 len, /* I: signal length */
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const SKP_int Order /* I: filter order, must be even */
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)
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{
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SKP_int k, j, idx, Order_half = SKP_RSHIFT( Order, 1 );
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SKP_int32 SA, SB, out32_Q10, out32;
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/* Order must be even */
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SKP_assert( 2 * Order_half == Order );
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/* S[] values are in Q14 */
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for( k = 0; k < len; k++ ) {
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SA = S[ Order - 1 ];
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out32_Q10 = 0;
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for( j = 0; j < ( Order_half - 1 ); j++ ) {
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idx = SKP_SMULBB( 2, j ) + 1;
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SB = S[ Order - 1 - idx ];
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S[ Order - 1 - idx ] = SA;
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out32_Q10 = SKP_SMLAWB( out32_Q10, SA, A_Q12[ ( j << 1 ) ] );
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out32_Q10 = SKP_SMLAWB( out32_Q10, SB, A_Q12[ ( j << 1 ) + 1 ] );
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SA = S[ Order - 2 - idx ];
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S[ Order - 2 - idx ] = SB;
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}
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/* unrolled loop: epilog */
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SB = S[ 0 ];
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S[ 0 ] = SA;
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out32_Q10 = SKP_SMLAWB( out32_Q10, SA, A_Q12[ Order - 2 ] );
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out32_Q10 = SKP_SMLAWB( out32_Q10, SB, A_Q12[ Order - 1 ] );
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/* apply gain to excitation signal and add to prediction */
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out32_Q10 = SKP_ADD_SAT32( out32_Q10, SKP_SMULWB( Gain_Q26, in[ k ] ) );
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/* scale to Q0 */
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out32 = SKP_RSHIFT_ROUND( out32_Q10, 10 );
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/* saturate output */
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out[ k ] = ( SKP_int16 )SKP_SAT16( out32 );
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/* move result into delay line */
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S[ Order - 1 ] = SKP_LSHIFT_SAT32( out32_Q10, 4 );
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}
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}
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