FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/eac3dec.c
Date: 2025-06-01 09:29:47
Exec Total Coverage
Lines: 259 309 83.8%
Functions: 4 4 100.0%
Branches: 196 262 74.8%
Line Branch Exec Source
1 /*
2 * E-AC-3 decoder
3 * Copyright (c) 2007 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
4 * Copyright (c) 2008 Justin Ruggles
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 /*
24 * There are several features of E-AC-3 that this decoder does not yet support.
25 *
26 * Enhanced Coupling
27 * No known samples exist. If any ever surface, this feature should not be
28 * too difficult to implement.
29 *
30 * Reduced Sample Rates
31 * No known samples exist. The spec also does not give clear information
32 * on how this is to be implemented.
33 *
34 * Transient Pre-noise Processing
35 * This is side information which a decoder should use to reduce artifacts
36 * caused by transients. There are samples which are known to have this
37 * information, but this decoder currently ignores it.
38 */
39
40
41 #include "avcodec.h"
42 #include "ac3.h"
43 #include "ac3_parser_internal.h"
44 #include "ac3dec.h"
45 #include "ac3dec_data.h"
46 #include "eac3_data.h"
47
48 /** gain adaptive quantization mode */
49 typedef enum {
50 EAC3_GAQ_NO =0,
51 EAC3_GAQ_12,
52 EAC3_GAQ_14,
53 EAC3_GAQ_124
54 } EAC3GaqMode;
55
56 #define EAC3_SR_CODE_REDUCED 3
57
58 3252 static void ff_eac3_apply_spectral_extension(AC3DecodeContext *s)
59 {
60 int bin, bnd, ch, i;
61 3252 uint8_t wrapflag[SPX_MAX_BANDS]={1,0,}, num_copy_sections, copy_sizes[SPX_MAX_BANDS];
62 float rms_energy[SPX_MAX_BANDS];
63
64 /* Set copy index mapping table. Set wrap flags to apply a notch filter at
65 wrap points later on. */
66 3252 bin = s->spx_dst_start_freq;
67 3252 num_copy_sections = 0;
68
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 10620 for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
69 int copysize;
70 7368 int bandsize = s->spx_band_sizes[bnd];
71
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 7368 if (bin + bandsize > s->spx_src_start_freq) {
72 ✗ copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq;
73 ✗ bin = s->spx_dst_start_freq;
74 ✗ wrapflag[bnd] = 1;
75 }
76
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 14736 for (i = 0; i < bandsize; i += copysize) {
77
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 7368 if (bin == s->spx_src_start_freq) {
78 ✗ copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq;
79 ✗ bin = s->spx_dst_start_freq;
80 }
81 7368 copysize = FFMIN(bandsize - i, s->spx_src_start_freq - bin);
82 7368 bin += copysize;
83 }
84 }
85 3252 copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq;
86
87
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 10620 for (ch = 1; ch <= s->fbw_channels; ch++) {
88
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 7368 if (!s->channel_uses_spx[ch])
89 ✗ continue;
90
91 /* Copy coeffs from normal bands to extension bands */
92 7368 bin = s->spx_src_start_freq;
93
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 14736 for (i = 0; i < num_copy_sections; i++) {
94 7368 memcpy(&s->transform_coeffs[ch][bin],
95 7368 &s->transform_coeffs[ch][s->spx_dst_start_freq],
96 7368 copy_sizes[i]*sizeof(INTFLOAT));
97 7368 bin += copy_sizes[i];
98 }
99
100 /* Calculate RMS energy for each SPX band. */
101 7368 bin = s->spx_src_start_freq;
102
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 26424 for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
103 19056 int bandsize = s->spx_band_sizes[bnd];
104 19056 float accum = 0.0f;
105
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 265008 for (i = 0; i < bandsize; i++) {
106 245952 float coeff = s->transform_coeffs[ch][bin++];
107 245952 accum += coeff * coeff;
108 }
109 19056 rms_energy[bnd] = sqrtf(accum / bandsize);
110 }
111
112 /* Apply a notch filter at transitions between normal and extension
113 bands and at all wrap points. */
114
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 7368 if (s->spx_atten_code[ch] >= 0) {
115 6330 const float *atten_tab = ff_eac3_spx_atten_tab[s->spx_atten_code[ch]];
116 6330 bin = s->spx_src_start_freq - 2;
117
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 20196 for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
118
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 13866 if (wrapflag[bnd]) {
119 6330 INTFLOAT *coeffs = &s->transform_coeffs[ch][bin];
120 6330 coeffs[0] *= atten_tab[0];
121 6330 coeffs[1] *= atten_tab[1];
122 6330 coeffs[2] *= atten_tab[2];
123 6330 coeffs[3] *= atten_tab[1];
124 6330 coeffs[4] *= atten_tab[0];
125 }
126 13866 bin += s->spx_band_sizes[bnd];
127 }
128 }
129
130 /* Apply noise-blended coefficient scaling based on previously
131 calculated RMS energy, blending factors, and SPX coordinates for
132 each band. */
133 7368 bin = s->spx_src_start_freq;
134
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 26424 for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
135 19056 float nscale = s->spx_noise_blend[ch][bnd] * rms_energy[bnd] * (1.0f / INT32_MIN);
136 19056 float sscale = s->spx_signal_blend[ch][bnd];
137 #if USE_FIXED
138 // spx_noise_blend and spx_signal_blend are both FP.23
139 ✗ nscale *= 1.0 / (1<<23);
140 ✗ sscale *= 1.0 / (1<<23);
141 ✗ if (nscale < -1.0)
142 ✗ nscale = -1.0;
143 #endif
144
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 265008 for (i = 0; i < s->spx_band_sizes[bnd]; i++) {
145 245952 UINTFLOAT noise = (INTFLOAT)(nscale * (int32_t)av_lfg_get(&s->dith_state));
146 245952 s->transform_coeffs[ch][bin] *= sscale;
147 245952 s->transform_coeffs[ch][bin++] += noise;
148 }
149 }
150 }
151 3252 }
152
153
154 /** lrint(M_SQRT2*cos(2*M_PI/12)*(1<<23)) */
155 #define COEFF_0 10273905LL
156
157 /** lrint(M_SQRT2*cos(0*M_PI/12)*(1<<23)) = lrint(M_SQRT2*(1<<23)) */
158 #define COEFF_1 11863283LL
159
160 /** lrint(M_SQRT2*cos(5*M_PI/12)*(1<<23)) */
161 #define COEFF_2 3070444LL
162
163 /**
164 * Calculate 6-point IDCT of the pre-mantissas.
165 * All calculations are 24-bit fixed-point.
166 */
167 99870 static void idct6(int pre_mant[6])
168 {
169 int tmp;
170 int even0, even1, even2, odd0, odd1, odd2;
171
172 99870 odd1 = pre_mant[1] - pre_mant[3] - pre_mant[5];
173
174 99870 even2 = ( pre_mant[2] * COEFF_0) >> 23;
175 99870 tmp = ( pre_mant[4] * COEFF_1) >> 23;
176 99870 odd0 = ((pre_mant[1] + pre_mant[5]) * COEFF_2) >> 23;
177
178 99870 even0 = pre_mant[0] + (tmp >> 1);
179 99870 even1 = pre_mant[0] - tmp;
180
181 99870 tmp = even0;
182 99870 even0 = tmp + even2;
183 99870 even2 = tmp - even2;
184
185 99870 tmp = odd0;
186 99870 odd0 = tmp + pre_mant[1] + pre_mant[3];
187 99870 odd2 = tmp + pre_mant[5] - pre_mant[3];
188
189 99870 pre_mant[0] = even0 + odd0;
190 99870 pre_mant[1] = even1 + odd1;
191 99870 pre_mant[2] = even2 + odd2;
192 99870 pre_mant[3] = even2 - odd2;
193 99870 pre_mant[4] = even1 - odd1;
194 99870 pre_mant[5] = even0 - odd0;
195 99870 }
196
197 816 static void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch)
198 {
199 int bin, blk, gs;
200 int end_bap, gaq_mode;
201 816 GetBitContext *gbc = &s->gbc;
202 int gaq_gain[AC3_MAX_COEFS];
203
204 816 gaq_mode = get_bits(gbc, 2);
205
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 816 end_bap = (gaq_mode < 2) ? 12 : 17;
206
207 /* if GAQ gain is used, decode gain codes for bins with hebap between
208 8 and end_bap */
209 816 gs = 0;
210
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 816 if (gaq_mode == EAC3_GAQ_12 || gaq_mode == EAC3_GAQ_14) {
211 /* read 1-bit GAQ gain codes */
212
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 88262 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
213
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 87559 if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < end_bap)
214 31648 gaq_gain[gs++] = get_bits1(gbc) << (gaq_mode-1);
215 }
216
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 113 } else if (gaq_mode == EAC3_GAQ_124) {
217 /* read 1.67-bit GAQ gain codes (3 codes in 5 bits) */
218 52 int gc = 2;
219
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 6560 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
220
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 6508 if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < 17) {
221
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 1905 if (gc++ == 2) {
222 655 int group_code = get_bits(gbc, 5);
223
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 655 if (group_code > 26) {
224 ✗ av_log(s->avctx, AV_LOG_WARNING, "GAQ gain group code out-of-range\n");
225 ✗ group_code = 26;
226 }
227 655 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][0];
228 655 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][1];
229 655 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][2];
230 655 gc = 0;
231 }
232 }
233 }
234 }
235
236 816 gs=0;
237
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 100686 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
238 99870 int hebap = s->bap[ch][bin];
239 99870 int bits = ff_eac3_bits_vs_hebap[hebap];
240
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 99870 if (!hebap) {
241 /* zero-mantissa dithering */
242
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 224756 for (blk = 0; blk < 6; blk++) {
243 192648 s->pre_mantissa[ch][bin][blk] = (av_lfg_get(&s->dith_state) & 0x7FFFFF) - 0x400000;
244 }
245
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 67762 } else if (hebap < 8) {
246 /* Vector Quantization */
247 31275 int v = get_bits(gbc, bits);
248
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 218925 for (blk = 0; blk < 6; blk++) {
249 187650 s->pre_mantissa[ch][bin][blk] = ff_eac3_mantissa_vq[hebap][v][blk] * (1 << 8);
250 }
251 } else {
252 /* Gain Adaptive Quantization */
253 int gbits, log_gain;
254
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 36487 if (gaq_mode != EAC3_GAQ_NO && hebap < end_bap) {
255 33553 log_gain = gaq_gain[gs++];
256 } else {
257 2934 log_gain = 0;
258 }
259 36487 gbits = bits - log_gain;
260
261
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 255409 for (blk = 0; blk < 6; blk++) {
262 218922 int mant = get_sbits(gbc, gbits);
263
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 218922 if (log_gain && mant == -(1 << (gbits-1))) {
264 /* large mantissa */
265 int b;
266 24721 int mbits = bits - (2 - log_gain);
267 24721 mant = get_sbits(gbc, mbits);
268 24721 mant = ((unsigned)mant) << (23 - (mbits - 1));
269 /* remap mantissa value to correct for asymmetric quantization */
270
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 24721 if (mant >= 0)
271 12278 b = 1 << (23 - log_gain);
272 else
273 12443 b = ff_eac3_gaq_remap_2_4_b[hebap-8][log_gain-1] * (1 << 8);
274 24721 mant += ((ff_eac3_gaq_remap_2_4_a[hebap-8][log_gain-1] * (int64_t)mant) >> 15) + b;
275 } else {
276 /* small mantissa, no GAQ, or Gk=1 */
277 194201 mant *= (1 << 24 - bits);
278
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 194201 if (!log_gain) {
279 /* remap mantissa value for no GAQ or Gk=1 */
280 115788 mant += (ff_eac3_gaq_remap_1[hebap-8] * (int64_t)mant) >> 15;
281 }
282 }
283 218922 s->pre_mantissa[ch][bin][blk] = mant;
284 }
285 }
286 99870 idct6(s->pre_mantissa[ch][bin]);
287 }
288 816 }
289
290 1204 static int ff_eac3_parse_header(AC3DecodeContext *s)
291 {
292 int i, blk, ch;
293 int ac3_exponent_strategy, parse_aht_info, parse_spx_atten_data;
294 int parse_transient_proc_info;
295 int num_cpl_blocks;
296 1204 GetBitContext *gbc = &s->gbc;
297
298 /* An E-AC-3 stream can have multiple independent streams which the
299 application can select from. each independent stream can also contain
300 dependent streams which are used to add or replace channels. */
301
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 1204 if (s->frame_type == EAC3_FRAME_TYPE_RESERVED) {
302 ✗ av_log(s->avctx, AV_LOG_ERROR, "Reserved frame type\n");
303 ✗ return AC3_PARSE_ERROR_FRAME_TYPE;
304 }
305
306 /* The substream id indicates which substream this frame belongs to. each
307 independent stream has its own substream id, and the dependent streams
308 associated to an independent stream have matching substream id's. */
309
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 1204 if (s->substreamid) {
310 /* only decode substream with id=0. skip any additional substreams. */
311 ✗ if (!s->eac3_subsbtreamid_found) {
312 ✗ s->eac3_subsbtreamid_found = 1;
313 ✗ avpriv_request_sample(s->avctx, "Additional substreams");
314 }
315 ✗ return AC3_PARSE_ERROR_FRAME_TYPE;
316 }
317
318
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 1204 if (s->bit_alloc_params.sr_code == EAC3_SR_CODE_REDUCED) {
319 /* The E-AC-3 specification does not tell how to handle reduced sample
320 rates in bit allocation. The best assumption would be that it is
321 handled like AC-3 DolbyNet, but we cannot be sure until we have a
322 sample which utilizes this feature. */
323 ✗ avpriv_request_sample(s->avctx, "Reduced sampling rate");
324 ✗ return AVERROR_PATCHWELCOME;
325 }
326 1204 skip_bits(gbc, 5); // skip bitstream id
327
328 /* volume control params */
329
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 2408 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
330 1204 s->dialog_normalization[i] = -get_bits(gbc, 5);
331
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 1204 if (s->dialog_normalization[i] == 0) {
332 ✗ s->dialog_normalization[i] = -31;
333 }
334
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 1204 if (s->target_level != 0) {
335 ✗ s->level_gain[i] = powf(2.0f,
336 ✗ (float)(s->target_level - s->dialog_normalization[i])/6.0f);
337 }
338 1204 s->compression_exists[i] = get_bits1(gbc);
339
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 1204 if (s->compression_exists[i]) {
340 930 s->heavy_dynamic_range[i] = AC3_HEAVY_RANGE(get_bits(gbc, 8));
341 }
342 }
343
344 /* dependent stream channel map */
345
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 1204 if (s->frame_type == EAC3_FRAME_TYPE_DEPENDENT) {
346
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 159 if (get_bits1(gbc)) {
347 159 int64_t channel_layout = 0;
348 159 int channel_map = get_bits(gbc, 16);
349 159 av_log(s->avctx, AV_LOG_DEBUG, "channel_map: %0X\n", channel_map);
350
351
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 2703 for (i = 0; i < 16; i++)
352
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 2544 if (channel_map & (1 << (EAC3_MAX_CHANNELS - i - 1)))
353 477 channel_layout |= ff_eac3_custom_channel_map_locations[i][1];
354
355
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 159 if (av_popcount64(channel_layout) > EAC3_MAX_CHANNELS) {
356 ✗ return AVERROR_INVALIDDATA;
357 }
358 159 s->channel_map = channel_map;
359 }
360 }
361
362 /* mixing metadata */
363
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 1204 if (get_bits1(gbc)) {
364 /* center and surround mix levels */
365
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 640 if (s->channel_mode > AC3_CHMODE_STEREO) {
366 146 s->preferred_downmix = get_bits(gbc, 2);
367
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 146 if (s->channel_mode & 1) {
368 /* if three front channels exist */
369 146 s->center_mix_level_ltrt = get_bits(gbc, 3);
370 146 s->center_mix_level = get_bits(gbc, 3);
371 }
372
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 146 if (s->channel_mode & 4) {
373 /* if a surround channel exists */
374 146 s->surround_mix_level_ltrt = av_clip(get_bits(gbc, 3), 3, 7);
375 146 s->surround_mix_level = av_clip(get_bits(gbc, 3), 3, 7);
376 }
377 }
378
379 /* lfe mix level */
380
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 640 if (s->lfe_on && (s->lfe_mix_level_exists = get_bits1(gbc))) {
381 146 s->lfe_mix_level = get_bits(gbc, 5);
382 }
383
384 /* info for mixing with other streams and substreams */
385
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 640 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT) {
386
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 1280 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
387 // TODO: apply program scale factor
388
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 640 if (get_bits1(gbc)) {
389 ✗ skip_bits(gbc, 6); // skip program scale factor
390 }
391 }
392
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 640 if (get_bits1(gbc)) {
393 ✗ skip_bits(gbc, 6); // skip external program scale factor
394 }
395 /* skip mixing parameter data */
396
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 640 switch(get_bits(gbc, 2)) {
397 ✗ case 1: skip_bits(gbc, 5); break;
398 ✗ case 2: skip_bits(gbc, 12); break;
399 ✗ case 3: {
400 ✗ int mix_data_size = (get_bits(gbc, 5) + 2) << 3;
401 ✗ skip_bits_long(gbc, mix_data_size);
402 ✗ break;
403 }
404 }
405 /* skip pan information for mono or dual mono source */
406
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 640 if (s->channel_mode < AC3_CHMODE_STEREO) {
407 ✗ for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
408 ✗ if (get_bits1(gbc)) {
409 /* note: this is not in the ATSC A/52B specification
410 reference: ETSI TS 102 366 V1.1.1
411 section: E.1.3.1.25 */
412 ✗ skip_bits(gbc, 8); // skip pan mean direction index
413 ✗ skip_bits(gbc, 6); // skip reserved paninfo bits
414 }
415 }
416 }
417 /* skip mixing configuration information */
418
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 640 if (get_bits1(gbc)) {
419 ✗ for (blk = 0; blk < s->num_blocks; blk++) {
420 ✗ if (s->num_blocks == 1 || get_bits1(gbc)) {
421 ✗ skip_bits(gbc, 5);
422 }
423 }
424 }
425 }
426 }
427
428 /* informational metadata */
429
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 1204 if (get_bits1(gbc)) {
430 771 s->bitstream_mode = get_bits(gbc, 3);
431 771 skip_bits(gbc, 2); // skip copyright bit and original bitstream bit
432
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 771 if (s->channel_mode == AC3_CHMODE_STEREO) {
433 625 s->dolby_surround_mode = get_bits(gbc, 2);
434 625 s->dolby_headphone_mode = get_bits(gbc, 2);
435 }
436
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 771 if (s->channel_mode >= AC3_CHMODE_2F2R) {
437 146 s->dolby_surround_ex_mode = get_bits(gbc, 2);
438 }
439
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 1542 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
440
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 771 if (get_bits1(gbc)) {
441 771 skip_bits(gbc, 8); // skip mix level, room type, and A/D converter type
442 }
443 }
444
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 771 if (s->bit_alloc_params.sr_code != EAC3_SR_CODE_REDUCED) {
445 771 skip_bits1(gbc); // skip source sample rate code
446 }
447 }
448
449 /* converter synchronization flag
450 If frames are less than six blocks, this bit should be turned on
451 once every 6 blocks to indicate the start of a frame set.
452 reference: RFC 4598, Section 2.1.3 Frame Sets */
453
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 1204 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && s->num_blocks != 6) {
454 98 skip_bits1(gbc); // skip converter synchronization flag
455 }
456
457 /* original frame size code if this stream was converted from AC-3 */
458
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 1204 if (s->frame_type == EAC3_FRAME_TYPE_AC3_CONVERT &&
459 ✗ (s->num_blocks == 6 || get_bits1(gbc))) {
460 ✗ skip_bits(gbc, 6); // skip frame size code
461 }
462
463 /* additional bitstream info */
464
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 1204 if (get_bits1(gbc)) {
465 159 int addbsil = get_bits(gbc, 6);
466
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 477 for (i = 0; i < addbsil + 1; i++) {
467
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 318 if (i == 0) {
468 /* In this 8 bit chunk, the LSB is equal to flag_ec3_extension_type_a
469 which can be used to detect Atmos presence */
470 159 skip_bits(gbc, 7);
471
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 159 if (get_bits1(gbc)) {
472 159 s->eac3_extension_type_a = 1;
473 }
474 } else {
475 159 skip_bits(gbc, 8); // skip additional bit stream info
476 }
477 }
478 }
479
480 /* audio frame syntax flags, strategy data, and per-frame data */
481
482
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 1204 if (s->num_blocks == 6) {
483 1106 ac3_exponent_strategy = get_bits1(gbc);
484 1106 parse_aht_info = get_bits1(gbc);
485 } else {
486 /* less than 6 blocks, so use AC-3-style exponent strategy syntax, and
487 do not use AHT */
488 98 ac3_exponent_strategy = 1;
489 98 parse_aht_info = 0;
490 }
491
492 1204 s->snr_offset_strategy = get_bits(gbc, 2);
493 1204 parse_transient_proc_info = get_bits1(gbc);
494
495 1204 s->block_switch_syntax = get_bits1(gbc);
496
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 1204 if (!s->block_switch_syntax)
497 1204 memset(s->block_switch, 0, sizeof(s->block_switch));
498
499 1204 s->dither_flag_syntax = get_bits1(gbc);
500
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 1204 if (!s->dither_flag_syntax) {
501
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 4368 for (ch = 1; ch <= s->fbw_channels; ch++)
502 3164 s->dither_flag[ch] = 1;
503 }
504 1204 s->dither_flag[CPL_CH] = s->dither_flag[s->lfe_ch] = 0;
505
506 1204 s->bit_allocation_syntax = get_bits1(gbc);
507
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 1204 if (!s->bit_allocation_syntax) {
508 /* set default bit allocation parameters */
509 918 s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[2];
510 918 s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[1];
511 918 s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab [1];
512 918 s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[2];
513 918 s->bit_alloc_params.floor = ff_ac3_floor_tab [7];
514 }
515
516 1204 s->fast_gain_syntax = get_bits1(gbc);
517 1204 s->dba_syntax = get_bits1(gbc);
518 1204 s->skip_syntax = get_bits1(gbc);
519 1204 parse_spx_atten_data = get_bits1(gbc);
520
521 /* coupling strategy occurrence and coupling use per block */
522 1204 num_cpl_blocks = 0;
523
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 1204 if (s->channel_mode > 1) {
524
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 7938 for (blk = 0; blk < s->num_blocks; blk++) {
525
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 6734 s->cpl_strategy_exists[blk] = (!blk || get_bits1(gbc));
526
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 6734 if (s->cpl_strategy_exists[blk]) {
527 1204 s->cpl_in_use[blk] = get_bits1(gbc);
528 } else {
529 5530 s->cpl_in_use[blk] = s->cpl_in_use[blk-1];
530 }
531 6734 num_cpl_blocks += s->cpl_in_use[blk];
532 }
533 } else {
534 ✗ memset(s->cpl_in_use, 0, sizeof(s->cpl_in_use));
535 }
536
537 /* exponent strategy data */
538
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 1204 if (ac3_exponent_strategy) {
539 /* AC-3-style exponent strategy syntax */
540
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 196 for (blk = 0; blk < s->num_blocks; blk++) {
541
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 588 for (ch = !s->cpl_in_use[blk]; ch <= s->fbw_channels; ch++) {
542 490 s->exp_strategy[blk][ch] = get_bits(gbc, 2);
543 }
544 }
545 } else {
546 /* LUT-based exponent strategy syntax */
547
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 4185 for (ch = !((s->channel_mode > 1) && num_cpl_blocks); ch <= s->fbw_channels; ch++) {
548 3079 int frmchexpstr = get_bits(gbc, 5);
549
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 21553 for (blk = 0; blk < 6; blk++) {
550 18474 s->exp_strategy[blk][ch] = ff_eac3_frm_expstr[frmchexpstr][blk];
551 }
552 }
553 }
554 /* LFE exponent strategy */
555
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 1204 if (s->lfe_on) {
556
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 532 for (blk = 0; blk < s->num_blocks; blk++) {
557 386 s->exp_strategy[blk][s->lfe_ch] = get_bits1(gbc);
558 }
559 }
560 /* original exponent strategies if this stream was converted from AC-3 */
561
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 1204 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT &&
562
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 1045 (s->num_blocks == 6 || get_bits1(gbc))) {
563 963 skip_bits(gbc, 5 * s->fbw_channels); // skip converter channel exponent strategy
564 }
565
566 /* determine which channels use AHT */
567
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 1204 if (parse_aht_info) {
568 /* For AHT to be used, all non-zero blocks must reuse exponents from
569 the first block. Furthermore, for AHT to be used in the coupling
570 channel, all blocks must use coupling and use the same coupling
571 strategy. */
572 448 s->channel_uses_aht[CPL_CH]=0;
573
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 1536 for (ch = (num_cpl_blocks != 6); ch <= s->channels; ch++) {
574 1088 int use_aht = 1;
575
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 5550 for (blk = 1; blk < 6; blk++) {
576
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 4734 if ((s->exp_strategy[blk][ch] != EXP_REUSE) ||
577 ✗ (!ch && s->cpl_strategy_exists[blk])) {
578 272 use_aht = 0;
579 272 break;
580 }
581 }
582
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 1088 s->channel_uses_aht[ch] = use_aht && get_bits1(gbc);
583 }
584 } else {
585 756 memset(s->channel_uses_aht, 0, sizeof(s->channel_uses_aht));
586 }
587
588 /* per-frame SNR offset */
589
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 1204 if (!s->snr_offset_strategy) {
590 1204 int csnroffst = (get_bits(gbc, 6) - 15) << 4;
591 1204 int snroffst = (csnroffst + get_bits(gbc, 4)) << 2;
592
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 5718 for (ch = 0; ch <= s->channels; ch++)
593 4514 s->snr_offset[ch] = snroffst;
594 }
595
596 /* transient pre-noise processing data */
597
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 1204 if (parse_transient_proc_info) {
598 ✗ for (ch = 1; ch <= s->fbw_channels; ch++) {
599 ✗ if (get_bits1(gbc)) { // channel in transient processing
600 ✗ skip_bits(gbc, 10); // skip transient processing location
601 ✗ skip_bits(gbc, 8); // skip transient processing length
602 }
603 }
604 }
605
606 /* spectral extension attenuation data */
607
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 4368 for (ch = 1; ch <= s->fbw_channels; ch++) {
608
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 3164 if (parse_spx_atten_data && get_bits1(gbc)) {
609 1055 s->spx_atten_code[ch] = get_bits(gbc, 5);
610 } else {
611 2109 s->spx_atten_code[ch] = -1;
612 }
613 }
614
615 /* block start information */
616
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 1204 if (s->num_blocks > 1 && get_bits1(gbc)) {
617 /* reference: Section E2.3.2.27
618 nblkstrtbits = (numblks - 1) * (4 + ceiling(log2(words_per_frame)))
619 The spec does not say what this data is or what it's used for.
620 It is likely the offset of each block within the frame. */
621 ✗ int block_start_bits = (s->num_blocks-1) * (4 + av_log2(s->frame_size-2));
622 ✗ skip_bits_long(gbc, block_start_bits);
623 ✗ avpriv_request_sample(s->avctx, "Block start info");
624 }
625
626 /* syntax state initialization */
627
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 4368 for (ch = 1; ch <= s->fbw_channels; ch++) {
628 3164 s->first_spx_coords[ch] = 1;
629 3164 s->first_cpl_coords[ch] = 1;
630 }
631 1204 s->first_cpl_leak = 1;
632
633 1204 return 0;
634 }
635