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 /* Could be set to 3 to save an additional bit at the cost of little quality */
37 /* Coefficient resolution in short windows */
38 #define TNS_Q_BITS_IS8 4
40 /* Define this to save a bit, be warned decoders can't deal with it
41 * so it is not lossless despite what the specifications say */
42 // #define TNS_ENABLE_COEF_COMPRESSION
44 /* TNS will only be used if the LPC gain is within these margins */
45 #define TNS_GAIN_THRESHOLD_LOW 1.477f
46 #define TNS_GAIN_THRESHOLD_HIGH 7.0f
47 #define TNS_GAIN_THRESHOLD_LOW_IS8 0.16f*TNS_GAIN_THRESHOLD_LOW
48 #define TNS_GAIN_THRESHOLD_HIGH_IS8 0.26f*TNS_GAIN_THRESHOLD_HIGH
50 static inline int compress_coeffs(int *coef, int order, int c_bits)
53 const int low_idx = c_bits ? 4 : 2;
54 const int shift_val = c_bits ? 8 : 4;
55 const int high_idx = c_bits ? 11 : 5;
56 #ifndef TNS_ENABLE_COEF_COMPRESSION
58 #endif /* TNS_ENABLE_COEF_COMPRESSION */
59 for (i = 0; i < order; i++)
60 if (coef[i] >= low_idx && coef[i] <= high_idx)
62 for (i = 0; i < order; i++)
63 coef[i] -= (coef[i] > high_idx) ? shift_val : 0;
69 * Coefficient compression is simply not lossless as it should be
70 * on any decoder tested and as such is not active.
72 void ff_aac_encode_tns_info(AACEncContext *s, SingleChannelElement *sce)
74 int i, w, filt, coef_compress = 0, coef_len;
75 TemporalNoiseShaping *tns = &sce->tns;
76 const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
77 const int c_bits = is8 ? TNS_Q_BITS_IS8 == 4 : TNS_Q_BITS == 4;
79 if (!sce->tns.present)
82 for (i = 0; i < sce->ics.num_windows; i++) {
83 put_bits(&s->pb, 2 - is8, sce->tns.n_filt[i]);
86 put_bits(&s->pb, 1, c_bits);
87 for (filt = 0; filt < tns->n_filt[i]; filt++) {
88 put_bits(&s->pb, 6 - 2 * is8, tns->length[i][filt]);
89 put_bits(&s->pb, 5 - 2 * is8, tns->order[i][filt]);
90 if (!tns->order[i][filt])
92 put_bits(&s->pb, 1, tns->direction[i][filt]);
93 coef_compress = compress_coeffs(tns->coef_idx[i][filt],
94 tns->order[i][filt], c_bits);
95 put_bits(&s->pb, 1, coef_compress);
96 coef_len = c_bits + 3 - coef_compress;
97 for (w = 0; w < tns->order[i][filt]; w++)
98 put_bits(&s->pb, coef_len, tns->coef_idx[i][filt][w]);
103 /* Apply TNS filter */
104 void ff_aac_apply_tns(AACEncContext *s, SingleChannelElement *sce)
106 TemporalNoiseShaping *tns = &sce->tns;
107 IndividualChannelStream *ics = &sce->ics;
108 int w, filt, m, i, top, order, bottom, start, end, size, inc;
109 const int mmm = FFMIN(ics->tns_max_bands, ics->max_sfb);
110 float lpc[TNS_MAX_ORDER], tmp[TNS_MAX_ORDER+1];
112 for (w = 0; w < ics->num_windows; w++) {
113 bottom = ics->num_swb;
114 for (filt = 0; filt < tns->n_filt[w]; filt++) {
116 bottom = FFMAX(0, top - tns->length[w][filt]);
117 order = tns->order[w][filt];
122 compute_lpc_coefs(tns->coef[w][filt], order, lpc, 0, 0, 0);
124 start = ics->swb_offset[FFMIN(bottom, mmm)];
125 end = ics->swb_offset[FFMIN( top, mmm)];
126 if ((size = end - start) <= 0)
128 if (tns->direction[w][filt]) {
136 if (!s->options.ltp) { // ar filter
137 for (m = 0; m < size; m++, start += inc) {
138 for (i = 1; i <= FFMIN(m, order); i++) {
139 sce->coeffs[start] += lpc[i-1]*sce->pcoeffs[start - i*inc];
142 } else { // ma filter
143 for (m = 0; m < size; m++, start += inc) {
144 tmp[0] = sce->pcoeffs[start];
145 for (i = 1; i <= FFMIN(m, order); i++)
146 sce->coeffs[start] += lpc[i-1]*tmp[i];
147 for (i = order; i > 0; i--)
156 * c_bits - 1 if 4 bit coefficients, 0 if 3 bit coefficients
158 static inline void quantize_coefs(double *coef, int *idx, float *lpc, int order,
162 const float *quant_arr = tns_tmp2_map[c_bits];
163 for (i = 0; i < order; i++) {
164 idx[i] = quant_array_idx((float)coef[i], quant_arr, c_bits ? 16 : 8);
165 lpc[i] = quant_arr[idx[i]];
170 * 3 bits per coefficient with 8 short windows
172 void ff_aac_search_for_tns(AACEncContext *s, SingleChannelElement *sce)
174 TemporalNoiseShaping *tns = &sce->tns;
175 double gain, coefs[MAX_LPC_ORDER];
176 int w, w2, g, count = 0;
177 const int mmm = FFMIN(sce->ics.tns_max_bands, sce->ics.max_sfb);
178 const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE;
179 const int c_bits = is8 ? TNS_Q_BITS_IS8 == 4 : TNS_Q_BITS == 4;
180 const int slant = sce->ics.window_sequence[0] == LONG_STOP_SEQUENCE ? 1 :
181 sce->ics.window_sequence[0] == LONG_START_SEQUENCE ? 0 : 2;
183 int sfb_start = av_clip(tns_min_sfb[is8][s->samplerate_index], 0, mmm);
184 int sfb_end = av_clip(sce->ics.num_swb, 0, mmm);
185 int order = is8 ? 5 : s->profile == FF_PROFILE_AAC_LOW ? 12 : TNS_MAX_ORDER;
187 for (w = 0; w < sce->ics.num_windows; w++) {
188 float en[2] = {0.0f, 0.0f};
189 int coef_start = w*sce->ics.num_swb + sce->ics.swb_offset[sfb_start];
190 int coef_len = sce->ics.swb_offset[sfb_end] - sce->ics.swb_offset[sfb_start];
192 for (g = 0; g < sce->ics.num_swb; g++) {
193 if (w*16+g < sfb_start || w*16+g > sfb_end)
195 for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {
196 FFPsyBand *band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];
197 if ((w+w2)*16+g > sfb_start + ((sfb_end - sfb_start)/2))
198 en[1] += band->energy;
200 en[0] += band->energy;
204 if (coef_len <= 0 || (sfb_end - sfb_start) <= 0)
208 gain = ff_lpc_calc_ref_coefs_f(&s->lpc, &sce->coeffs[coef_start],
209 coef_len, order, coefs);
211 if (!order || gain < TNS_GAIN_THRESHOLD_LOW || gain > TNS_GAIN_THRESHOLD_HIGH)
213 if (is8 && (gain < TNS_GAIN_THRESHOLD_LOW_IS8 || gain > TNS_GAIN_THRESHOLD_HIGH_IS8))
215 if (is8 || order < 2) {
217 for (g = 0; g < tns->n_filt[w]; g++) {
218 tns->length[w][g] = sfb_end - sfb_start;
219 tns->direction[w][g] = slant != 2 ? slant : en[0] < en[1];
220 tns->order[w][g] = order;
221 quantize_coefs(coefs, tns->coef_idx[w][g], tns->coef[w][g],
224 } else { /* 2 filters due to energy disbalance */
226 for (g = 0; g < tns->n_filt[w]; g++) {
227 tns->direction[w][g] = slant != 2 ? slant : en[g] < en[!g];
228 tns->order[w][g] = !g ? order/2 : order - tns->order[w][g-1];
229 tns->length[w][g] = !g ? (sfb_end - sfb_start)/2 : \
230 (sfb_end - sfb_start) - tns->length[w][g-1];
231 quantize_coefs(&coefs[!g ? 0 : order - tns->order[w][g-1]],
232 tns->coef_idx[w][g], tns->coef[w][g],
233 tns->order[w][g], c_bits);
236 count += tns->n_filt[w];
238 sce->tns.present = !!count;