220 lines
8.0 KiB
C
220 lines
8.0 KiB
C
/*
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* AAC encoder TNS
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* Copyright (C) 2015 Rostislav Pehlivanov
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* AAC encoder temporal noise shaping
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* @author Rostislav Pehlivanov ( atomnuker gmail com )
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*/
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#include "aacenc.h"
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#include "aacenc_tns.h"
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#include "aactab.h"
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#include "aacenc_utils.h"
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#include "aacenc_quantization.h"
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/*
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* Shifts the values as well if compression is possible.
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*/
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static inline int compress_coeffs(int *coef, int order, int c_bits)
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{
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int i, res = 0;
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const int low_idx = c_bits ? 4 : 2;
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const int shift_val = c_bits ? 8 : 4;
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const int high_idx = c_bits ? 11 : 5;
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for (i = 0; i < order; i++)
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if (coef[i] < low_idx || coef[i] > high_idx)
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res++;
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if (res == order)
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for (i = 0; i < order; i++)
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coef[i] -= (coef[i] > high_idx) ? shift_val : 0;
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return res == order;
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}
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/**
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* Encode TNS data.
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* Coefficient compression saves a single bit per coefficient.
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*/
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void ff_aac_encode_tns_info(AACEncContext *s, SingleChannelElement *sce)
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{
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int i, w, filt, coef_len, coef_compress = 0;
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const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
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TemporalNoiseShaping *tns = &sce->tns;
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const int c_bits = is8 ? TNS_Q_BITS_SHORT == 4 : TNS_Q_BITS == 4;
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if (!sce->tns.present)
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return;
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for (i = 0; i < sce->ics.num_windows; i++) {
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put_bits(&s->pb, 2 - is8, sce->tns.n_filt[i]);
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if (tns->n_filt[i]) {
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put_bits(&s->pb, 1, c_bits);
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for (filt = 0; filt < tns->n_filt[i]; filt++) {
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put_bits(&s->pb, 6 - 2 * is8, tns->length[i][filt]);
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put_bits(&s->pb, 5 - 2 * is8, tns->order[i][filt]);
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if (tns->order[i][filt]) {
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coef_compress = compress_coeffs(tns->coef_idx[i][filt],
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tns->order[i][filt], c_bits);
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put_bits(&s->pb, 1, !!tns->direction[i][filt]);
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put_bits(&s->pb, 1, !!coef_compress);
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coef_len = c_bits + 3 - coef_compress;
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for (w = 0; w < tns->order[i][filt]; w++)
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put_bits(&s->pb, coef_len, tns->coef_idx[i][filt][w]);
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}
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}
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}
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}
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}
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/* Apply TNS filter */
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void ff_aac_apply_tns(AACEncContext *s, SingleChannelElement *sce)
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{
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TemporalNoiseShaping *tns = &sce->tns;
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IndividualChannelStream *ics = &sce->ics;
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int w, filt, m, i, top, order, bottom, start, end, size, inc;
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const int mmm = FFMIN(ics->tns_max_bands, ics->max_sfb);
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float lpc[TNS_MAX_ORDER];
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for (w = 0; w < ics->num_windows; w++) {
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bottom = ics->num_swb;
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for (filt = 0; filt < tns->n_filt[w]; filt++) {
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top = bottom;
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bottom = FFMAX(0, top - tns->length[w][filt]);
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order = tns->order[w][filt];
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if (order == 0)
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continue;
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// tns_decode_coef
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compute_lpc_coefs(tns->coef[w][filt], order, lpc, 0, 0, 0);
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start = ics->swb_offset[FFMIN(bottom, mmm)];
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end = ics->swb_offset[FFMIN( top, mmm)];
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if ((size = end - start) <= 0)
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continue;
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if (tns->direction[w][filt]) {
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inc = -1;
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start = end - 1;
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} else {
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inc = 1;
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}
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start += w * 128;
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// ar filter
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for (m = 0; m < size; m++, start += inc)
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for (i = 1; i <= FFMIN(m, order); i++)
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sce->coeffs[start] += lpc[i-1]*sce->pcoeffs[start - i*inc];
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}
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}
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}
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/*
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* c_bits - 1 if 4 bit coefficients, 0 if 3 bit coefficients
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*/
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static inline void quantize_coefs(double *coef, int *idx, float *lpc, int order,
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int c_bits)
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{
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int i;
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const float *quant_arr = tns_tmp2_map[c_bits];
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for (i = 0; i < order; i++) {
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idx[i] = quant_array_idx((float)coef[i], quant_arr, c_bits ? 16 : 8);
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lpc[i] = quant_arr[idx[i]];
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}
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}
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/*
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* 3 bits per coefficient with 8 short windows
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*/
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void ff_aac_search_for_tns(AACEncContext *s, SingleChannelElement *sce)
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{
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TemporalNoiseShaping *tns = &sce->tns;
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int w, w2, g, count = 0;
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const int mmm = FFMIN(sce->ics.tns_max_bands, sce->ics.max_sfb);
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const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
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const int c_bits = is8 ? TNS_Q_BITS_SHORT == 4 : TNS_Q_BITS == 4;
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int sfb_start = av_clip(tns_min_sfb[is8][s->samplerate_index], 0, mmm);
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int sfb_end = av_clip(sce->ics.num_swb, 0, mmm);
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for (w = 0; w < sce->ics.num_windows; w++) {
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int use_tns;
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int order = is8 ? 5 : s->profile == FF_PROFILE_AAC_LOW ? 12 : TNS_MAX_ORDER;
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int coef_start = w*sce->ics.num_swb + sce->ics.swb_offset[sfb_start];
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int coef_len = sce->ics.swb_offset[sfb_end] - sce->ics.swb_offset[sfb_start];
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float e_ratio = 0.0f, threshold = 0.0f, spread = 0.0f, en[2] = {0.0, 0.0f};
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double gain = 0.0f, coefs[MAX_LPC_ORDER] = {0};
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for (g = 0; g < sce->ics.num_swb; g++) {
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if (w*16+g < sfb_start || w*16+g > sfb_end)
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continue;
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for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {
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FFPsyBand *band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];
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if ((w+w2)*16+g > sfb_start + ((sfb_end - sfb_start)/2))
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en[1] += band->energy;
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else
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en[0] += band->energy;
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threshold += band->threshold;
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spread += band->spread;
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}
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}
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if (coef_len <= 0 || (sfb_end - sfb_start) <= 0)
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continue;
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/* LPC */
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gain = ff_lpc_calc_ref_coefs_f(&s->lpc, &sce->coeffs[coef_start],
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coef_len, order, coefs);
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if (!order || gain < TNS_GAIN_THRESHOLD_LOW || gain > TNS_GAIN_THRESHOLD_HIGH)
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use_tns = 0;
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else if ((en[0]+en[1]) < TNS_GAIN_THRESHOLD_LOW*threshold || spread < TNS_SPREAD_THRESHOLD)
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use_tns = 0;
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else
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use_tns = 1;
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if (use_tns) {
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e_ratio = en[0]/en[1];
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if (is8 || order < 2 || (e_ratio > TNS_E_RATIO_LOW && e_ratio < TNS_E_RATIO_HIGH)) {
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tns->n_filt[w] = 1;
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for (g = 0; g < tns->n_filt[w]; g++) {
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tns->length[w][g] = sfb_end - sfb_start;
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tns->direction[w][g] = en[0] < en[1];
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tns->order[w][g] = order;
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quantize_coefs(coefs, tns->coef_idx[w][g], tns->coef[w][g],
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order, c_bits);
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}
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} else { /* 2 filters due to energy disbalance */
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tns->n_filt[w] = 2;
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for (g = 0; g < tns->n_filt[w]; g++) {
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tns->direction[w][g] = en[g] < en[!g];
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tns->order[w][g] = !g ? order/2 : order - tns->order[w][g-1];
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tns->length[w][g] = !g ? (sfb_end - sfb_start)/2 : \
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(sfb_end - sfb_start) - tns->length[w][g-1];
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quantize_coefs(&coefs[!g ? 0 : order - tns->order[w][g-1]],
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tns->coef_idx[w][g], tns->coef[w][g],
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tns->order[w][g], c_bits);
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}
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}
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count++;
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}
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}
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sce->tns.present = !!count;
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}
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