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73 lines
3.2 KiB
C
73 lines
3.2 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, are permitted provided that the following conditions
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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 Internet Society, IETF or IETF Trust, nor the
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names of specific contributors, may be used to endorse or promote
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products derived from this software without specific prior written
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permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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***********************************************************************/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "SigProc_FIX.h"
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#include "SigProc_FLP.h"
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#include "define.h"
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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 silk_a2k_FLP() */
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silk_float silk_LPC_inverse_pred_gain_FLP( /* O return inverse prediction gain, energy domain */
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const silk_float *A, /* I prediction coefficients [order] */
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opus_int32 order /* I prediction order */
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)
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{
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opus_int k, n;
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double invGain, rc, rc_mult1, rc_mult2, tmp1, tmp2;
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silk_float Atmp[ SILK_MAX_ORDER_LPC ];
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silk_memcpy( Atmp, A, order * sizeof(silk_float) );
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invGain = 1.0;
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for( k = order - 1; k > 0; k-- ) {
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rc = -Atmp[ k ];
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rc_mult1 = 1.0f - rc * rc;
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invGain *= rc_mult1;
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if( invGain * MAX_PREDICTION_POWER_GAIN < 1.0f ) {
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return 0.0f;
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}
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rc_mult2 = 1.0f / rc_mult1;
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for( n = 0; n < (k + 1) >> 1; n++ ) {
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tmp1 = Atmp[ n ];
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tmp2 = Atmp[ k - n - 1 ];
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Atmp[ n ] = (silk_float)( ( tmp1 - tmp2 * rc ) * rc_mult2 );
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Atmp[ k - n - 1 ] = (silk_float)( ( tmp2 - tmp1 * rc ) * rc_mult2 );
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}
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}
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rc = -Atmp[ 0 ];
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rc_mult1 = 1.0f - rc * rc;
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invGain *= rc_mult1;
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if( invGain * MAX_PREDICTION_POWER_GAIN < 1.0f ) {
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return 0.0f;
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}
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return (silk_float)invGain;
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}
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