ref: 75ff53c70e7e2b8781dadd21a84be3056e1cde69
dir: /silk/silk_schur.c/
/*********************************************************************** Copyright (c) 2006-2011, Skype Limited. All rights reserved. Redistribution and use in source and binary forms, with or without modification, (subject to the limitations in the disclaimer below) are permitted provided that the following conditions are met: - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. - Neither the name of Skype Limited, nor the names of specific contributors, may be used to endorse or promote products derived from this software without specific prior written permission. NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED BY THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ***********************************************************************/ #ifdef HAVE_CONFIG_H #include "config.h" #endif #include "silk_SigProc_FIX.h" /* Faster than schur64(), but much less accurate. */ /* uses SMLAWB(), requiring armv5E and higher. */ opus_int32 silk_schur( /* O: Returns residual energy */ opus_int16 *rc_Q15, /* O: reflection coefficients [order] Q15 */ const opus_int32 *c, /* I: correlations [order+1] */ const opus_int32 order /* I: prediction order */ ) { opus_int k, n, lz; opus_int32 C[ SILK_MAX_ORDER_LPC + 1 ][ 2 ]; opus_int32 Ctmp1, Ctmp2, rc_tmp_Q15; /* Get number of leading zeros */ lz = silk_CLZ32( c[ 0 ] ); /* Copy correlations and adjust level to Q30 */ if( lz < 2 ) { /* lz must be 1, so shift one to the right */ for( k = 0; k < order + 1; k++ ) { C[ k ][ 0 ] = C[ k ][ 1 ] = SKP_RSHIFT( c[ k ], 1 ); } } else if( lz > 2 ) { /* Shift to the left */ lz -= 2; for( k = 0; k < order + 1; k++ ) { C[ k ][ 0 ] = C[ k ][ 1 ] = SKP_LSHIFT( c[ k ], lz ); } } else { /* No need to shift */ for( k = 0; k < order + 1; k++ ) { C[ k ][ 0 ] = C[ k ][ 1 ] = c[ k ]; } } for( k = 0; k < order; k++ ) { /* Get reflection coefficient */ rc_tmp_Q15 = -SKP_DIV32_16( C[ k + 1 ][ 0 ], SKP_max_32( SKP_RSHIFT( C[ 0 ][ 1 ], 15 ), 1 ) ); /* Clip (shouldn't happen for properly conditioned inputs) */ rc_tmp_Q15 = SKP_SAT16( rc_tmp_Q15 ); /* Store */ rc_Q15[ k ] = ( opus_int16 )rc_tmp_Q15; /* Update correlations */ for( n = 0; n < order - k; n++ ) { Ctmp1 = C[ n + k + 1 ][ 0 ]; Ctmp2 = C[ n ][ 1 ]; C[ n + k + 1 ][ 0 ] = SKP_SMLAWB( Ctmp1, SKP_LSHIFT( Ctmp2, 1 ), rc_tmp_Q15 ); C[ n ][ 1 ] = SKP_SMLAWB( Ctmp2, SKP_LSHIFT( Ctmp1, 1 ), rc_tmp_Q15 ); } } /* return residual energy */ return C[ 0 ][ 1 ]; }