73 lines
3.7 KiB
C
73 lines
3.7 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_biquad.c *
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* *
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* Second order ARMA filter *
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* Can handle slowly varying filter coefficients *
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* *
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* Copyright 2006 (c), Skype Limited *
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* Date: 060221 *
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* */
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#include "SKP_Silk_SigProc_FIX.h"
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/* Second order ARMA filter */
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/* Can handle slowly varying filter coefficients */
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void SKP_Silk_biquad(
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const SKP_int16 *in, /* I: input signal */
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const SKP_int16 *B, /* I: MA coefficients, Q13 [3] */
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const SKP_int16 *A, /* I: AR coefficients, Q13 [2] */
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SKP_int32 *S, /* I/O: state vector [2] */
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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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)
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{
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SKP_int k, in16;
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SKP_int32 A0_neg, A1_neg, S0, S1, out32, tmp32;
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S0 = S[ 0 ];
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S1 = S[ 1 ];
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A0_neg = -A[ 0 ];
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A1_neg = -A[ 1 ];
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for( k = 0; k < len; k++ ) {
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/* S[ 0 ], S[ 1 ]: Q13 */
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in16 = in[ k ];
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out32 = SKP_SMLABB( S0, in16, B[ 0 ] );
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S0 = SKP_SMLABB( S1, in16, B[ 1 ] );
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S0 += SKP_LSHIFT( SKP_SMULWB( out32, A0_neg ), 3 );
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S1 = SKP_LSHIFT( SKP_SMULWB( out32, A1_neg ), 3 );
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S1 = SKP_SMLABB( S1, in16, B[ 2 ] );
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tmp32 = SKP_RSHIFT_ROUND( out32, 13 ) + 1;
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out[ k ] = (SKP_int16)SKP_SAT16( tmp32 );
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}
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S[ 0 ] = S0;
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S[ 1 ] = S1;
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}
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