93 lines
3.9 KiB
C
93 lines
3.9 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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/* Faster than schur64(), but much less accurate. */
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/* uses SMLAWB(), requiring armv5E and higher. */
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opus_int32 silk_schur( /* O Returns residual energy */
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opus_int16 *rc_Q15, /* O reflection coefficients [order] Q15 */
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const opus_int32 *c, /* I correlations [order+1] */
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const opus_int32 order /* I prediction order */
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)
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{
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opus_int k, n, lz;
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opus_int32 C[ SILK_MAX_ORDER_LPC + 1 ][ 2 ];
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opus_int32 Ctmp1, Ctmp2, rc_tmp_Q15;
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silk_assert( order==6||order==8||order==10||order==12||order==14||order==16 );
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/* Get number of leading zeros */
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lz = silk_CLZ32( c[ 0 ] );
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/* Copy correlations and adjust level to Q30 */
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if( lz < 2 ) {
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/* lz must be 1, so shift one to the right */
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for( k = 0; k < order + 1; k++ ) {
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C[ k ][ 0 ] = C[ k ][ 1 ] = silk_RSHIFT( c[ k ], 1 );
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}
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} else if( lz > 2 ) {
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/* Shift to the left */
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lz -= 2;
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for( k = 0; k < order + 1; k++ ) {
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C[ k ][ 0 ] = C[ k ][ 1 ] = silk_LSHIFT( c[ k ], lz );
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}
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} else {
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/* No need to shift */
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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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}
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for( k = 0; k < order; k++ ) {
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/* Get reflection coefficient */
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rc_tmp_Q15 = -silk_DIV32_16( C[ k + 1 ][ 0 ], silk_max_32( silk_RSHIFT( C[ 0 ][ 1 ], 15 ), 1 ) );
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/* Clip (shouldn't happen for properly conditioned inputs) */
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rc_tmp_Q15 = silk_SAT16( rc_tmp_Q15 );
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/* Store */
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rc_Q15[ k ] = (opus_int16)rc_tmp_Q15;
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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 ] = silk_SMLAWB( Ctmp1, silk_LSHIFT( Ctmp2, 1 ), rc_tmp_Q15 );
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C[ n ][ 1 ] = silk_SMLAWB( Ctmp2, silk_LSHIFT( Ctmp1, 1 ), rc_tmp_Q15 );
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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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