3 * Copyright (C) 2015 Rostislav Pehlivanov
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 * AAC encoder temporal noise shaping
25 * @author Rostislav Pehlivanov ( atomnuker gmail com )
29 #include "aacenc_tns.h"
31 #include "aacenc_utils.h"
32 #include "aacenc_quantization.h"
34 /* Define this to save a bit, be warned decoders can't deal with it
35 * so it is not lossless despite what the specifications say */
36 // #define TNS_ENABLE_COEF_COMPRESSION
38 static inline int compress_coeffs(int *coef, int order, int c_bits)
41 const int low_idx = c_bits ? 4 : 2;
42 const int shift_val = c_bits ? 8 : 4;
43 const int high_idx = c_bits ? 11 : 5;
44 #ifndef TNS_ENABLE_COEF_COMPRESSION
46 #endif /* TNS_ENABLE_COEF_COMPRESSION */
47 for (i = 0; i < order; i++)
48 if (coef[i] >= low_idx && coef[i] <= high_idx)
50 for (i = 0; i < order; i++)
51 coef[i] -= (coef[i] > high_idx) ? shift_val : 0;
57 * Coefficient compression is simply not lossless as it should be
58 * on any decoder tested and as such is not active.
60 void ff_aac_encode_tns_info(AACEncContext *s, SingleChannelElement *sce)
62 int i, w, filt, coef_compress = 0, coef_len;
63 TemporalNoiseShaping *tns = &sce->tns;
64 const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
65 const int c_bits = is8 ? TNS_Q_BITS_IS8 == 4 : TNS_Q_BITS == 4;
67 if (!sce->tns.present)
70 for (i = 0; i < sce->ics.num_windows; i++) {
71 put_bits(&s->pb, 2 - is8, sce->tns.n_filt[i]);
74 put_bits(&s->pb, 1, c_bits);
75 for (filt = 0; filt < tns->n_filt[i]; filt++) {
76 put_bits(&s->pb, 6 - 2 * is8, tns->length[i][filt]);
77 put_bits(&s->pb, 5 - 2 * is8, tns->order[i][filt]);
78 if (!tns->order[i][filt])
80 put_bits(&s->pb, 1, tns->direction[i][filt]);
81 coef_compress = compress_coeffs(tns->coef_idx[i][filt],
82 tns->order[i][filt], c_bits);
83 put_bits(&s->pb, 1, coef_compress);
84 coef_len = c_bits + 3 - coef_compress;
85 for (w = 0; w < tns->order[i][filt]; w++)
86 put_bits(&s->pb, coef_len, tns->coef_idx[i][filt][w]);
91 /* Apply TNS filter */
92 void ff_aac_apply_tns(AACEncContext *s, SingleChannelElement *sce)
94 TemporalNoiseShaping *tns = &sce->tns;
95 IndividualChannelStream *ics = &sce->ics;
96 int w, filt, m, i, top, order, bottom, start, end, size, inc;
97 const int mmm = FFMIN(ics->tns_max_bands, ics->max_sfb);
98 float lpc[TNS_MAX_ORDER], tmp[TNS_MAX_ORDER+1];
100 for (w = 0; w < ics->num_windows; w++) {
101 bottom = ics->num_swb;
102 for (filt = 0; filt < tns->n_filt[w]; filt++) {
104 bottom = FFMAX(0, top - tns->length[w][filt]);
105 order = tns->order[w][filt];
110 compute_lpc_coefs(tns->coef[w][filt], order, lpc, 0, 0, 0);
112 start = ics->swb_offset[FFMIN(bottom, mmm)];
113 end = ics->swb_offset[FFMIN( top, mmm)];
114 if ((size = end - start) <= 0)
116 if (tns->direction[w][filt]) {
124 if (!s->options.ltp) { // ar filter
125 for (m = 0; m < size; m++, start += inc) {
126 for (i = 1; i <= FFMIN(m, order); i++) {
127 sce->coeffs[start] += lpc[i-1]*sce->pcoeffs[start - i*inc];
130 } else { // ma filter
131 for (m = 0; m < size; m++, start += inc) {
132 tmp[0] = sce->pcoeffs[start];
133 for (i = 1; i <= FFMIN(m, order); i++)
134 sce->coeffs[start] += lpc[i-1]*tmp[i];
135 for (i = order; i > 0; i--)
144 * c_bits - 1 if 4 bit coefficients, 0 if 3 bit coefficients
146 static inline void quantize_coefs(double *coef, int *idx, float *lpc, int order,
150 const float *quant_arr = tns_tmp2_map[c_bits];
151 for (i = 0; i < order; i++) {
152 idx[i] = quant_array_idx((float)coef[i], quant_arr, c_bits ? 16 : 8);
153 lpc[i] = quant_arr[idx[i]];
158 * 3 bits per coefficient with 8 short windows
160 void ff_aac_search_for_tns(AACEncContext *s, SingleChannelElement *sce)
162 TemporalNoiseShaping *tns = &sce->tns;
163 int w, w2, g, count = 0;
164 const int mmm = FFMIN(sce->ics.tns_max_bands, sce->ics.max_sfb);
165 const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
166 const int c_bits = is8 ? TNS_Q_BITS_SHORT == 4 : TNS_Q_BITS == 4;
168 int sfb_start = av_clip(tns_min_sfb[is8][s->samplerate_index], 0, mmm);
169 int sfb_end = av_clip(sce->ics.num_swb, 0, mmm);
171 for (w = 0; w < sce->ics.num_windows; w++) {
173 int order = is8 ? 5 : s->profile == FF_PROFILE_AAC_LOW ? 12 : TNS_MAX_ORDER;
174 int coef_start = w*sce->ics.num_swb + sce->ics.swb_offset[sfb_start];
175 int coef_len = sce->ics.swb_offset[sfb_end] - sce->ics.swb_offset[sfb_start];
176 float e_ratio = 0.0f, threshold = 0.0f, spread = 0.0f, en[2] = {0.0, 0.0f};
177 double gain = 0.0f, coefs[MAX_LPC_ORDER] = {0};
179 for (g = 0; g < sce->ics.num_swb; g++) {
180 if (w*16+g < sfb_start || w*16+g > sfb_end)
182 for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {
183 FFPsyBand *band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];
184 if ((w+w2)*16+g > sfb_start + ((sfb_end - sfb_start)/2))
185 en[1] += band->energy;
187 en[0] += band->energy;
188 threshold += band->threshold;
189 spread += band->spread;
193 if (coef_len <= 0 || (sfb_end - sfb_start) <= 0)
197 gain = ff_lpc_calc_ref_coefs_f(&s->lpc, &sce->coeffs[coef_start],
198 coef_len, order, coefs);
200 if (!order || gain < TNS_GAIN_THRESHOLD_LOW || gain > TNS_GAIN_THRESHOLD_HIGH)
202 else if ((en[0]+en[1]) < TNS_GAIN_THRESHOLD_LOW*threshold || spread < TNS_SPREAD_THRESHOLD)
208 e_ratio = en[0]/en[1];
209 if (is8 || order < 2 || (e_ratio > TNS_E_RATIO_LOW && e_ratio < TNS_E_RATIO_HIGH)) {
211 for (g = 0; g < tns->n_filt[w]; g++) {
212 tns->length[w][g] = sfb_end - sfb_start;
213 tns->direction[w][g] = en[0] < en[1];
214 tns->order[w][g] = order;
215 quantize_coefs(coefs, tns->coef_idx[w][g], tns->coef[w][g],
218 } else { /* 2 filters due to energy disbalance */
220 for (g = 0; g < tns->n_filt[w]; g++) {
221 tns->direction[w][g] = en[g] < en[!g];
222 tns->order[w][g] = !g ? order/2 : order - tns->order[w][g-1];
223 tns->length[w][g] = !g ? (sfb_end - sfb_start)/2 : \
224 (sfb_end - sfb_start) - tns->length[w][g-1];
225 quantize_coefs(&coefs[!g ? 0 : order - tns->order[w][g-1]],
226 tns->coef_idx[w][g], tns->coef[w][g],
227 tns->order[w][g], c_bits);
233 sce->tns.present = !!count;