ref: bfc67b95e207cb2143ba5d67f396645c98929d9b
dir: /silk/LPC_analysis_filter.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 "SigProc_FIX.h" /*******************************************/ /* LPC analysis filter */ /* NB! State is kept internally and the */ /* filter always starts with zero state */ /* first d output samples are set to zero */ /*******************************************/ void silk_LPC_analysis_filter( opus_int16 *out, /* O: Output signal */ const opus_int16 *in, /* I: Input signal */ const opus_int16 *B, /* I: MA prediction coefficients, Q12 [order] */ const opus_int32 len, /* I: Signal length */ const opus_int32 d /* I: Filter order */ ) { opus_int ix, j; opus_int32 out32_Q12, out32; const opus_int16 *in_ptr; silk_assert( d >= 6 ); silk_assert( (d & 1) == 0 ); silk_assert( d <= len ); for ( ix = d; ix < len; ix++) { in_ptr = &in[ ix - 1 ]; out32_Q12 = silk_SMULBB( in_ptr[ 0 ], B[ 0 ] ); out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -1 ], B[ 1 ] ); out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -2 ], B[ 2 ] ); out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -3 ], B[ 3 ] ); out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -4 ], B[ 4 ] ); out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -5 ], B[ 5 ] ); for( j = 6; j < d; j += 2 ) { out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -j ], B[ j ] ); out32_Q12 = silk_SMLABB( out32_Q12, in_ptr[ -j - 1 ], B[ j + 1 ] ); } /* Subtract prediction */ out32_Q12 = silk_SUB32( silk_LSHIFT( (opus_int32)in_ptr[ 1 ], 12 ), out32_Q12 ); /* Scale to Q0 */ out32 = silk_RSHIFT_ROUND( out32_Q12, 12 ); /* Saturate output */ out[ ix ] = ( opus_int16 )silk_SAT16( out32 ); } /* Set first d output samples to zero */ silk_memset( out, 0, d * sizeof( opus_int16 ) ); }