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74 lines
3.4 KiB
C
74 lines
3.4 KiB
C
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/***********************************************************************
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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_schur.c *
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* *
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* Calculates the reflection coefficients from the correlation sequence *
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* *
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* Copyright 2008 (c), Skype Limited *
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* Date: 080103 *
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*/
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#include "SKP_Silk_SigProc_FLP.h"
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SKP_float SKP_Silk_schur_FLP( /* O returns residual energy */
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SKP_float refl_coef[], /* O reflection coefficients (length order) */
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const SKP_float auto_corr[], /* I autotcorrelation sequence (length order+1) */
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SKP_int order /* I order */
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)
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{
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SKP_int k, n;
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SKP_float C[SKP_Silk_MAX_ORDER_LPC + 1][2];
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SKP_float Ctmp1, Ctmp2, rc_tmp;
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/* copy correlations */
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for( k = 0; k < order+1; k++ ){
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C[k][0] = C[k][1] = auto_corr[k];
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}
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for( k = 0; k < order; k++ ) {
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/* get reflection coefficient */
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rc_tmp = -C[k + 1][0] / SKP_max_float( C[0][1], 1e-9f );
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/* save the output */
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refl_coef[k] = rc_tmp;
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/* update correlations */
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for( n = 0; n < order - k; n++ ){
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Ctmp1 = C[n + k + 1][0];
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Ctmp2 = C[n][1];
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C[n + k + 1][0] = Ctmp1 + Ctmp2 * rc_tmp;
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C[n][1] = Ctmp2 + Ctmp1 * rc_tmp;
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}
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}
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/* return residual energy */
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return C[0][1];
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}
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