81 lines
4.2 KiB
C
81 lines
4.2 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, (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_schur64.c *
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* *
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* Calculates the reflection coefficients from the correlation sequence *
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* using extra precision *
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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_FIX.h"
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/* Slower than schur(), but more accurate. */
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/* Uses SMULL(), available on armv4 */
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SKP_int32 SKP_Silk_schur64( /* O: Returns residual energy */
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SKP_int32 rc_Q16[], /* O: Reflection coefficients [order] Q16 */
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const SKP_int32 c[], /* I: Correlations [order+1] */
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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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SKP_int32 C[ SKP_Silk_MAX_ORDER_LPC + 1 ][ 2 ];
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SKP_int32 Ctmp1_Q30, Ctmp2_Q30, rc_tmp_Q31;
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/* Check for invalid input */
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if( c[ 0 ] <= 0 ) {
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SKP_memset( rc_Q16, 0, order * sizeof( SKP_int32 ) );
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return 0;
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}
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for( k = 0; k < order + 1; k++ ) {
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C[ k ][ 0 ] = C[ k ][ 1 ] = c[ k ];
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}
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for( k = 0; k < order; k++ ) {
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/* Get reflection coefficient: divide two Q30 values and get result in Q31 */
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rc_tmp_Q31 = SKP_DIV32_varQ( -C[ k + 1 ][ 0 ], C[ 0 ][ 1 ], 31 );
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/* Save the output */
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rc_Q16[ k ] = SKP_RSHIFT_ROUND( rc_tmp_Q31, 15 );
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/* Update correlations */
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for( n = 0; n < order - k; n++ ) {
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Ctmp1_Q30 = C[ n + k + 1 ][ 0 ];
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Ctmp2_Q30 = C[ n ][ 1 ];
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/* Multiply and add the highest int32 */
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C[ n + k + 1 ][ 0 ] = Ctmp1_Q30 + SKP_SMMUL( SKP_LSHIFT( Ctmp2_Q30, 1 ), rc_tmp_Q31 );
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C[ n ][ 1 ] = Ctmp2_Q30 + SKP_SMMUL( SKP_LSHIFT( Ctmp1_Q30, 1 ), rc_tmp_Q31 );
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}
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}
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return C[ 0 ][ 1 ];
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}
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