82 lines
4.0 KiB
C
Executable File
82 lines
4.0 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_inverse_pred_gain.c *
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* *
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* compute inverse of LPC prediction gain, and *
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* test if LPC coefficients are stable (all poles within unit circle) *
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* *
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* Copyright 2008 (c), Skype Limited *
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* */
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#include "SKP_Silk_SigProc_FIX.h"
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#include "SKP_Silk_SigProc_FLP.h"
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#define RC_THRESHOLD 0.9999f
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/* compute inverse of LPC prediction gain, and */
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/* test if LPC coefficients are stable (all poles within unit circle) */
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/* this code is based on SKP_Silk_a2k_FLP() */
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SKP_int SKP_Silk_LPC_inverse_pred_gain_FLP( /* O: returns 1 if unstable, otherwise 0 */
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SKP_float *invGain, /* O: inverse prediction gain, energy domain */
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const SKP_float *A, /* I: prediction coefficients [order] */
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SKP_int32 order /* I: prediction order */
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)
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{
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SKP_int k, n;
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double rc, rc_mult1, rc_mult2;
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SKP_float Atmp[ 2 ][ SKP_Silk_MAX_ORDER_LPC ];
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SKP_float *Aold, *Anew;
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Anew = Atmp[ order & 1 ];
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SKP_memcpy( Anew, A, order * sizeof(SKP_float) );
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*invGain = 1.0f;
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for( k = order - 1; k > 0; k-- ) {
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rc = -Anew[ k ];
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if (rc > RC_THRESHOLD || rc < -RC_THRESHOLD) {
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return 1;
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}
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rc_mult1 = 1.0f - rc * rc;
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rc_mult2 = 1.0f / rc_mult1;
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*invGain *= (SKP_float)rc_mult1;
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/* swap pointers */
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Aold = Anew;
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Anew = Atmp[ k & 1 ];
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for( n = 0; n < k; n++ ) {
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Anew[ n ] = (SKP_float)( ( Aold[ n ] - Aold[ k - n - 1 ] * rc ) * rc_mult2 );
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}
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}
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rc = -Anew[ 0 ];
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if ( rc > RC_THRESHOLD || rc < -RC_THRESHOLD ) {
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return 1;
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}
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rc_mult1 = 1.0f - rc * rc;
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*invGain *= (SKP_float)rc_mult1;
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return 0;
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}
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