f6e781ab8b
- Merged the LPC stabilization from NLSF2A_stable.c into NLSF2A.c - The bandwidth expansion in NLSF2A() now operates on int32 LPC coefficients in Q17 domain (instead of int16 Q12 coefficients) - The function bwexpander_32() has a more precise way of updating the chirp variable (round to nearest, instead of round down) - Changed a few variables in NLSF_stabilize() from int16 to int32 to avoid signed wrap-around (no difference in results as the wrap-around would always be reversed later) - The LSF codebook for WB speech has a quantization stepsize of 0.15 (was 0.16). This doesn't break the bitstream, although it slightly limits quality of signals encoded with the old version and decoded with the new one (I can't really hear it and PESQ gives high scores as well). I does improve handling of tonal signals. - As discussed: the Q-domain of the poly function is now in Q16 (was Q20) - As discussed: limiting the LSFs in NLSF_decode() to 0...32767 - The silk_NLSF_DELTA_MIN values were lowered to deal with a possible future situation with less or no input HP filtering.
109 lines
5.8 KiB
C
109 lines
5.8 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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#include "silk_main_FLP.h"
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#include "silk_tuning_parameters.h"
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void silk_find_LPC_FLP(
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SKP_int16 NLSF_Q15[], /* O NLSFs */
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SKP_int8 *interpIndex, /* O NLSF interp. index for NLSF interp. */
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const SKP_int16 prev_NLSFq_Q15[], /* I Previous NLSFs, for NLSF interpolation */
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const SKP_int useInterpNLSFs, /* I Flag */
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const SKP_int firstFrameAfterReset, /* I Flag */
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const SKP_int LPC_order, /* I LPC order */
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const SKP_float x[], /* I Input signal */
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const SKP_int subfr_length, /* I Subframe length incl preceeding samples */
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const SKP_int nb_subfr /* I: Number of subframes */
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)
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{
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SKP_int k;
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SKP_float a[ MAX_LPC_ORDER ];
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/* Used only for NLSF interpolation */
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double res_nrg, res_nrg_2nd, res_nrg_interp;
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SKP_int16 NLSF0_Q15[ MAX_LPC_ORDER ];
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SKP_float a_tmp[ MAX_LPC_ORDER ];
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SKP_float LPC_res[ ( MAX_FRAME_LENGTH + MAX_NB_SUBFR * MAX_LPC_ORDER ) / 2 ];
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/* Default: No interpolation */
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*interpIndex = 4;
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/* Burg AR analysis for the full frame */
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res_nrg = silk_burg_modified_FLP( a, x, subfr_length, nb_subfr, FIND_LPC_COND_FAC, LPC_order );
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if( firstFrameAfterReset ) {
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silk_bwexpander_FLP( a, LPC_order, FIND_LPC_CHIRP_FIRST_FRAME );
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} else {
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silk_bwexpander_FLP( a_tmp, LPC_order, FIND_LPC_CHIRP );
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}
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if( useInterpNLSFs && !firstFrameAfterReset && nb_subfr == MAX_NB_SUBFR ) {
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/* Optimal solution for last 10 ms; subtract residual energy here, as that's easier than */
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/* adding it to the residual energy of the first 10 ms in each iteration of the search below */
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res_nrg -= silk_burg_modified_FLP( a_tmp, x + ( MAX_NB_SUBFR / 2 ) * subfr_length,
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subfr_length, MAX_NB_SUBFR / 2, FIND_LPC_COND_FAC, LPC_order );
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silk_bwexpander_FLP( a_tmp, LPC_order, FIND_LPC_CHIRP );
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/* Convert to NLSFs */
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silk_A2NLSF_FLP( NLSF_Q15, a_tmp, LPC_order );
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/* Search over interpolation indices to find the one with lowest residual energy */
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res_nrg_2nd = SKP_float_MAX;
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for( k = 3; k >= 0; k-- ) {
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/* Interpolate NLSFs for first half */
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silk_interpolate( NLSF0_Q15, prev_NLSFq_Q15, NLSF_Q15, k, LPC_order );
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/* Convert to LPC for residual energy evaluation */
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silk_NLSF2A_FLP( a_tmp, NLSF0_Q15, LPC_order );
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/* Calculate residual energy with LSF interpolation */
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silk_LPC_analysis_filter_FLP( LPC_res, a_tmp, x, 2 * subfr_length, LPC_order );
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res_nrg_interp =
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silk_energy_FLP( LPC_res + LPC_order, subfr_length - LPC_order ) +
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silk_energy_FLP( LPC_res + LPC_order + subfr_length, subfr_length - LPC_order );
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/* Determine whether current interpolated NLSFs are best so far */
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if( res_nrg_interp < res_nrg ) {
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/* Interpolation has lower residual energy */
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res_nrg = res_nrg_interp;
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*interpIndex = (SKP_int8)k;
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} else if( res_nrg_interp > res_nrg_2nd ) {
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/* No reason to continue iterating - residual energies will continue to climb */
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break;
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}
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res_nrg_2nd = res_nrg_interp;
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}
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}
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if( *interpIndex == 4 ) {
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/* NLSF interpolation is currently inactive, calculate NLSFs from full frame AR coefficients */
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silk_A2NLSF_FLP( NLSF_Q15, a, LPC_order );
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}
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SKP_assert( *interpIndex == 4 || ( useInterpNLSFs && !firstFrameAfterReset && nb_subfr == MAX_NB_SUBFR ) );
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}
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