ref: 839de4d0823a5affc8a4b8b797f5080d2c3bb385
dir: /silk/float/LPC_inv_pred_gain_FLP.c/
/*********************************************************************** Copyright (c) 2006-2011, 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. ***********************************************************************/ #ifdef HAVE_CONFIG_H #include "config.h" #endif #include "SigProc_FIX.h" #include "SigProc_FLP.h" #define RC_THRESHOLD 0.9999f /* compute inverse of LPC prediction gain, and */ /* test if LPC coefficients are stable (all poles within unit circle) */ /* this code is based on silk_a2k_FLP() */ opus_int silk_LPC_inverse_pred_gain_FLP( /* O: returns 1 if unstable, otherwise 0 */ silk_float *invGain, /* O: inverse prediction gain, energy domain */ const silk_float *A, /* I: prediction coefficients [order] */ opus_int32 order /* I: prediction order */ ) { opus_int k, n; double rc, rc_mult1, rc_mult2; silk_float Atmp[ 2 ][ SILK_MAX_ORDER_LPC ]; silk_float *Aold, *Anew; Anew = Atmp[ order & 1 ]; silk_memcpy( Anew, A, order * sizeof(silk_float) ); *invGain = 1.0f; for( k = order - 1; k > 0; k-- ) { rc = -Anew[ k ]; if (rc > RC_THRESHOLD || rc < -RC_THRESHOLD) { return 1; } rc_mult1 = 1.0f - rc * rc; rc_mult2 = 1.0f / rc_mult1; *invGain *= (silk_float)rc_mult1; /* swap pointers */ Aold = Anew; Anew = Atmp[ k & 1 ]; for( n = 0; n < k; n++ ) { Anew[ n ] = (silk_float)( ( Aold[ n ] - Aold[ k - n - 1 ] * rc ) * rc_mult2 ); } } rc = -Anew[ 0 ]; if ( rc > RC_THRESHOLD || rc < -RC_THRESHOLD ) { return 1; } rc_mult1 = 1.0f - rc * rc; *invGain *= (silk_float)rc_mult1; return 0; }