78 lines
3.5 KiB
C
78 lines
3.5 KiB
C
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/***********************************************************************
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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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/* Slower than schur(), but more accurate. */
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/* Uses SMULL(), available on armv4 */
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opus_int32 silk_schur64( /* O returns residual energy */
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opus_int32 rc_Q16[], /* O Reflection coefficients [order] Q16 */
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const opus_int32 c[], /* I Correlations [order+1] */
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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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opus_int32 C[ SILK_MAX_ORDER_LPC + 1 ][ 2 ];
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opus_int32 Ctmp1_Q30, Ctmp2_Q30, rc_tmp_Q31;
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silk_assert( order==6||order==8||order==10||order==12||order==14||order==16 );
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/* Check for invalid input */
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if( c[ 0 ] <= 0 ) {
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silk_memset( rc_Q16, 0, order * sizeof( opus_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 = silk_DIV32_varQ( -C[ k + 1 ][ 0 ], C[ 0 ][ 1 ], 31 );
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/* Save the output */
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rc_Q16[ k ] = silk_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 + silk_SMMUL( silk_LSHIFT( Ctmp2_Q30, 1 ), rc_tmp_Q31 );
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C[ n ][ 1 ] = Ctmp2_Q30 + silk_SMMUL( silk_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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