FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/ac3_parser.c
Date: 2026-08-26 16:21:34
Exec Total Coverage
Lines: 216 243 88.9%
Functions: 8 8 100.0%
Branches: 146 184 79.3%
Line Branch Exec Source
1 /*
2 * AC-3 parser
3 * Copyright (c) 2003 Fabrice Bellard
4 * Copyright (c) 2003 Michael Niedermayer
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 #include "config_components.h"
24
25 #include "libavutil/channel_layout.h"
26 #include "libavutil/mem.h"
27 #include "parser.h"
28 #include "ac3defs.h"
29 #include "ac3tab.h"
30 #include "ac3_parser.h"
31 #include "ac3_parser_internal.h"
32 #include "aac_ac3_parser.h"
33 #include "get_bits.h"
34 #include "parser_internal.h"
35
36
37 #define AC3_HEADER_SIZE 7
38
39 #if CONFIG_AC3_PARSER
40
41 static const uint8_t eac3_blocks[4] = {
42 1, 2, 3, 6
43 };
44
45 /**
46 * Table for center mix levels
47 * reference: Section 5.4.2.4 cmixlev
48 */
49 static const uint8_t center_levels[4] = { 4, 5, 6, 5 };
50
51 /**
52 * Table for surround mix levels
53 * reference: Section 5.4.2.5 surmixlev
54 */
55 static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };
56
57 11063 int ff_ac3_find_syncword(const uint8_t *buf, int buf_size)
58 {
59 int i;
60
61
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 12471 for (i = 1; i < buf_size; i += 2) {
62
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 12460 if (buf[i] == 0x77 || buf[i] == 0x0B) {
63
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 11060 if ((buf[i] ^ buf[i-1]) == (0x77 ^ 0x0B)) {
64 11052 i--;
65 11052 break;
66
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 8 } else if ((buf[i] ^ buf[i+1]) == (0x77 ^ 0x0B)) {
67 ✗ break;
68 }
69 }
70 }
71
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 11063 if (i >= buf_size)
72 11 return AVERROR_INVALIDDATA;
73
74 11052 return i;
75 }
76
77 /**
78 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
79 * GetBitContext within AC3DecodeContext must point to
80 * the start of the synchronized AC-3 bitstream.
81 */
82 18418 static int ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
83 {
84 /* read the rest of the bsi. read twice for dual mono mode. */
85
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 43458 for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
86 25040 hdr->dialog_normalization[i] = -get_bits(gbc, 5);
87 25040 hdr->compression_exists[i] = get_bits1(gbc);
88
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 25040 if (hdr->compression_exists[i])
89 8882 hdr->heavy_dynamic_range[i] = get_bits(gbc, 8);
90
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 25040 if (get_bits1(gbc))
91 1030 skip_bits(gbc, 8); //skip language code
92
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 25040 if (get_bits1(gbc))
93 5881 skip_bits(gbc, 7); //skip audio production information
94 }
95
96 18418 skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
97
98 /* skip the timecodes or parse the Alternate Bit Stream Syntax */
99
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 18418 if (hdr->bitstream_id != 6) {
100
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 15542 if (get_bits1(gbc))
101 1960 skip_bits(gbc, 14); //skip timecode1
102
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 15542 if (get_bits1(gbc))
103 1850 skip_bits(gbc, 14); //skip timecode2
104 } else {
105
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 2876 if (get_bits1(gbc)) {
106 1719 hdr->preferred_downmix = get_bits(gbc, 2);
107 1719 hdr->center_mix_level_ltrt = get_bits(gbc, 3);
108 1719 hdr->surround_mix_level_ltrt = av_clip(get_bits(gbc, 3), 3, 7);
109 1719 hdr->center_mix_level = get_bits(gbc, 3);
110 1719 hdr->surround_mix_level = av_clip(get_bits(gbc, 3), 3, 7);
111 }
112
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 2876 if (get_bits1(gbc)) {
113 1705 hdr->dolby_surround_ex_mode = get_bits(gbc, 2);
114 1705 hdr->dolby_headphone_mode = get_bits(gbc, 2);
115 1705 skip_bits(gbc, 10); // skip adconvtyp (1), xbsi2 (8), encinfo (1)
116 }
117 }
118
119 /* skip additional bitstream info */
120
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 18418 if (get_bits1(gbc)) {
121 1940 int i = get_bits(gbc, 6);
122 do {
123 52508 skip_bits(gbc, 8);
124
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 52508 } while (i--);
125 }
126
127 18418 return 0;
128 }
129
130 119355 static int eac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
131 {
132
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 119355 if (hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
133 ✗ return AC3_PARSE_ERROR_FRAME_TYPE;
134
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 119355 if (hdr->substreamid)
135 13832 return AC3_PARSE_ERROR_FRAME_TYPE;
136
137 105523 skip_bits(gbc, 5); // skip bitstream id
138
139 /* volume control params */
140
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 212164 for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
141 106641 hdr->dialog_normalization[i] = -get_bits(gbc, 5);
142 106641 hdr->compression_exists[i] = get_bits1(gbc);
143
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 106641 if (hdr->compression_exists[i])
144 104281 hdr->heavy_dynamic_range[i] = get_bits(gbc, 8);
145 }
146
147 /* dependent stream channel map */
148
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 105523 if (hdr->frame_type == EAC3_FRAME_TYPE_DEPENDENT) {
149 2430 hdr->channel_map_present = get_bits1(gbc);
150
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 2430 if (hdr->channel_map_present) {
151 1645 int64_t channel_layout = 0;
152 1645 int channel_map = get_bits(gbc, 16);
153
154
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 27965 for (int i = 0; i < 16; i++)
155
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 26320 if (channel_map & (1 << (EAC3_MAX_CHANNELS - i - 1)))
156 4945 channel_layout |= ff_eac3_custom_channel_map_locations[i][1];
157
158
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 1645 if (av_popcount64(channel_layout) > EAC3_MAX_CHANNELS) {
159 ✗ return AC3_PARSE_ERROR_CHANNEL_MAP;
160 }
161 1645 hdr->channel_map = channel_map;
162 }
163 }
164
165 /* mixing metadata */
166
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 105523 if (get_bits1(gbc)) {
167 /* center and surround mix levels */
168
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 95080 if (hdr->channel_mode > AC3_CHMODE_STEREO) {
169 972 hdr->preferred_downmix = get_bits(gbc, 2);
170
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 972 if (hdr->channel_mode & 1) {
171 /* if three front channels exist */
172 972 hdr->center_mix_level_ltrt = get_bits(gbc, 3);
173 972 hdr->center_mix_level = get_bits(gbc, 3);
174 }
175
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 972 if (hdr->channel_mode & 4) {
176 /* if a surround channel exists */
177 972 hdr->surround_mix_level_ltrt = av_clip(get_bits(gbc, 3), 3, 7);
178 972 hdr->surround_mix_level = av_clip(get_bits(gbc, 3), 3, 7);
179 }
180 }
181
182 /* lfe mix level */
183
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 95080 if (hdr->lfe_on && (hdr->lfe_mix_level_exists = get_bits1(gbc))) {
184 968 hdr->lfe_mix_level = get_bits(gbc, 5);
185 }
186
187 /* info for mixing with other streams and substreams */
188
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 95080 if (hdr->frame_type == EAC3_FRAME_TYPE_INDEPENDENT) {
189
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 190152 for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
190 // TODO: apply program scale factor
191
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 95076 if (get_bits1(gbc)) {
192 ✗ skip_bits(gbc, 6); // skip program scale factor
193 }
194 }
195
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 95076 if (get_bits1(gbc)) {
196 ✗ skip_bits(gbc, 6); // skip external program scale factor
197 }
198 /* skip mixing parameter data */
199
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 95076 switch(get_bits(gbc, 2)) {
200 ✗ case 1: skip_bits(gbc, 5); break;
201 ✗ case 2: skip_bits(gbc, 12); break;
202 ✗ case 3: {
203 ✗ int mix_data_size = (get_bits(gbc, 5) + 2) << 3;
204 ✗ skip_bits_long(gbc, mix_data_size);
205 ✗ break;
206 }
207 }
208 /* skip pan information for mono or dual mono source */
209
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 95076 if (hdr->channel_mode < AC3_CHMODE_STEREO) {
210 ✗ for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
211 ✗ if (get_bits1(gbc)) {
212 /* note: this is not in the ATSC A/52B specification
213 reference: ETSI TS 102 366 V1.1.1
214 section: E.1.3.1.25 */
215 ✗ skip_bits(gbc, 8); // skip pan mean direction index
216 ✗ skip_bits(gbc, 6); // skip reserved paninfo bits
217 }
218 }
219 }
220 /* skip mixing configuration information */
221
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 95076 if (get_bits1(gbc)) {
222 ✗ for (int i = 0; i < hdr->num_blocks; i++) {
223 ✗ if (hdr->num_blocks == 1 || get_bits1(gbc)) {
224 ✗ skip_bits(gbc, 5);
225 }
226 }
227 }
228 }
229 }
230
231 /* informational metadata */
232
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 105523 if (get_bits1(gbc)) {
233 95810 hdr->bitstream_mode = get_bits(gbc, 3);
234 95810 skip_bits(gbc, 2); // skip copyright bit and original bitstream bit
235
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 95810 if (hdr->channel_mode == AC3_CHMODE_STEREO) {
236 94838 hdr->dolby_surround_mode = get_bits(gbc, 2);
237 94838 hdr->dolby_headphone_mode = get_bits(gbc, 2);
238 }
239
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 95810 if (hdr->channel_mode >= AC3_CHMODE_2F2R) {
240 972 hdr->dolby_surround_ex_mode = get_bits(gbc, 2);
241 }
242
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 191620 for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
243
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 95810 if (get_bits1(gbc)) {
244 95810 skip_bits(gbc, 8); // skip mix level, room type, and A/D converter type
245 }
246 }
247
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 95810 if (hdr->sr_code != EAC3_SR_CODE_REDUCED) {
248 95810 skip_bits1(gbc); // skip source sample rate code
249 }
250 }
251
252 /* converter synchronization flag
253 If frames are less than six blocks, this bit should be turned on
254 once every 6 blocks to indicate the start of a frame set.
255 reference: RFC 4598, Section 2.1.3 Frame Sets */
256
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 105523 if (hdr->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && hdr->num_blocks != 6) {
257 1994 skip_bits1(gbc); // skip converter synchronization flag
258 }
259
260 /* original frame size code if this stream was converted from AC-3 */
261
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 105523 if (hdr->frame_type == EAC3_FRAME_TYPE_AC3_CONVERT &&
262
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 4 (hdr->num_blocks == 6 || get_bits1(gbc))) {
263 ✗ skip_bits(gbc, 6); // skip frame size code
264 }
265
266 /* additional bitstream info */
267
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 105523 if (get_bits1(gbc)) {
268 1683 int addbsil = get_bits(gbc, 6);
269
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 3952 for (int i = 0; i < addbsil + 1; i++) {
270
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 2269 if (i == 0) {
271 /* In this 8 bit chunk, the LSB is equal to flag_ec3_extension_type_a
272 which can be used to detect Atmos presence */
273 1683 skip_bits(gbc, 7);
274 1683 hdr->eac3_extension_type_a = get_bits1(gbc);
275
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 1683 if (hdr->eac3_extension_type_a) {
276 1643 hdr->complexity_index_type_a = get_bits(gbc, 8);
277 1643 i++;
278 }
279 } else {
280 586 skip_bits(gbc, 8); // skip additional bit stream info
281 }
282 }
283 }
284
285 105523 return 0;
286 }
287
288 218525 int ff_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
289 {
290 int frame_size_code;
291
292 218525 memset(hdr, 0, sizeof(*hdr));
293
294 218525 hdr->sync_word = get_bits(gbc, 16);
295
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 218525 if(hdr->sync_word != 0x0B77)
296 68328 return AC3_PARSE_ERROR_SYNC;
297
298 /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
299 150197 hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F;
300
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 150197 if(hdr->bitstream_id > 16)
301 9974 return AC3_PARSE_ERROR_BSID;
302
303 140223 hdr->num_blocks = 6;
304 140223 hdr->ac3_bit_rate_code = -1;
305
306 /* set default mix levels */
307 140223 hdr->center_mix_level = 5; // -4.5dB
308 140223 hdr->surround_mix_level = 6; // -6.0dB
309
310 /* set default dolby surround mode */
311 140223 hdr->dolby_surround_mode = AC3_DSURMOD_NOTINDICATED;
312
313
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 140223 if(hdr->bitstream_id <= 10) {
314 /* Normal AC-3 */
315 20498 hdr->crc1 = get_bits(gbc, 16);
316 20498 hdr->sr_code = get_bits(gbc, 2);
317
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 20498 if(hdr->sr_code == 3)
318 558 return AC3_PARSE_ERROR_SAMPLE_RATE;
319
320 19940 frame_size_code = get_bits(gbc, 6);
321
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 19940 if(frame_size_code > 37)
322 1522 return AC3_PARSE_ERROR_FRAME_SIZE;
323
324 18418 hdr->ac3_bit_rate_code = (frame_size_code >> 1);
325
326 18418 skip_bits(gbc, 5); // skip bsid, already got it
327
328 18418 hdr->bitstream_mode = get_bits(gbc, 3);
329 18418 hdr->channel_mode = get_bits(gbc, 3);
330
331
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 18418 if(hdr->channel_mode == AC3_CHMODE_STEREO) {
332 3523 hdr->dolby_surround_mode = get_bits(gbc, 2);
333 } else {
334
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 14895 if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)
335 7421 hdr-> center_mix_level = center_levels[get_bits(gbc, 2)];
336
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 14895 if(hdr->channel_mode & 4)
337 7463 hdr->surround_mix_level = surround_levels[get_bits(gbc, 2)];
338 }
339 18418 hdr->lfe_on = get_bits1(gbc);
340
341 18418 hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
342 18418 hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
343 18418 hdr->bit_rate = (ff_ac3_bitrate_tab[hdr->ac3_bit_rate_code] * 1000) >> hdr->sr_shift;
344 18418 hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
345 18418 hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
346 18418 hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT;
347 18418 hdr->substreamid = 0;
348
349 18418 int ret = ac3_parse_header(gbc, hdr);
350
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 18418 if (ret < 0)
351 ✗ return ret;
352 } else {
353 /* Enhanced AC-3 */
354 119725 hdr->crc1 = 0;
355 119725 hdr->frame_type = get_bits(gbc, 2);
356
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 119725 if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
357 352 return AC3_PARSE_ERROR_FRAME_TYPE;
358
359 119373 hdr->substreamid = get_bits(gbc, 3);
360
361 119373 hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;
362
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 119373 if(hdr->frame_size < AC3_HEADER_SIZE)
363 ✗ return AC3_PARSE_ERROR_FRAME_SIZE;
364
365 119373 hdr->sr_code = get_bits(gbc, 2);
366
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 119373 if (hdr->sr_code == 3) {
367 110 int sr_code2 = get_bits(gbc, 2);
368
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 110 if(sr_code2 == 3)
369 18 return AC3_PARSE_ERROR_SAMPLE_RATE;
370 92 hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
371 92 hdr->sr_shift = 1;
372 } else {
373 119263 hdr->num_blocks = eac3_blocks[get_bits(gbc, 2)];
374 119263 hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
375 119263 hdr->sr_shift = 0;
376 }
377
378 119355 hdr->channel_mode = get_bits(gbc, 3);
379 119355 hdr->lfe_on = get_bits1(gbc);
380
381 119355 hdr->bit_rate = 8LL * hdr->frame_size * hdr->sample_rate /
382 119355 (hdr->num_blocks * 256);
383 119355 hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
384
385 119355 int ret = eac3_parse_header(gbc, hdr);
386
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 119355 if (ret < 0)
387 13832 return ret;
388 }
389 123941 hdr->channel_layout = ff_ac3_channel_layout_tab[hdr->channel_mode];
390
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 123941 if (hdr->lfe_on)
391 10499 hdr->channel_layout |= AV_CH_LOW_FREQUENCY;
392
393 123941 return 0;
394 }
395
396 // TODO: Better way to pass AC3HeaderInfo fields to mov muxer.
397 10032 int avpriv_ac3_parse_header(AC3HeaderInfo **phdr, const uint8_t *buf,
398 size_t size)
399 {
400 GetBitContext gb;
401 AC3HeaderInfo *hdr;
402 int err;
403
404
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 10032 if (!*phdr)
405 1641 *phdr = av_mallocz(sizeof(AC3HeaderInfo));
406
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 10032 if (!*phdr)
407 ✗ return AVERROR(ENOMEM);
408 10032 hdr = *phdr;
409
410 10032 err = init_get_bits8(&gb, buf, size);
411
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 10032 if (err < 0)
412 ✗ return AVERROR_INVALIDDATA;
413 10032 err = ff_ac3_parse_header(&gb, hdr);
414
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 10032 if (err < 0)
415 2 return AVERROR_INVALIDDATA;
416
417 10030 return get_bits_count(&gb);
418 }
419
420 143386 int av_ac3_parse_header(const uint8_t *buf, size_t size,
421 uint8_t *bitstream_id, uint16_t *frame_size)
422 {
423 GetBitContext gb;
424 AC3HeaderInfo hdr;
425 uint8_t tmp[32 + AV_INPUT_BUFFER_PADDING_SIZE];
426 int err;
427
428 143386 size = FFMIN(32, size);
429 143386 memcpy(tmp, buf, size);
430 143386 memset(tmp + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
431 143386 err = init_get_bits8(&gb, tmp, size);
432
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 143386 if (err < 0)
433 ✗ return AVERROR_INVALIDDATA;
434 143386 err = ff_ac3_parse_header(&gb, &hdr);
435
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 143386 if (err < 0)
436 42118 return AVERROR_INVALIDDATA;
437
438 101268 *bitstream_id = hdr.bitstream_id;
439 101268 *frame_size = hdr.frame_size;
440
441 101268 return 0;
442 }
443
444 60869 static int ac3_sync(uint64_t state, int *need_next_header, int *new_frame_start)
445 {
446 int err;
447 union {
448 uint64_t u64;
449 uint8_t u8[8 + AV_INPUT_BUFFER_PADDING_SIZE];
450 60869 } tmp = { av_be2ne64(state) };
451 AC3HeaderInfo hdr;
452 GetBitContext gbc;
453
454
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 60869 if (tmp.u8[1] == 0x77 && tmp.u8[2] == 0x0b) {
455 ✗ FFSWAP(uint8_t, tmp.u8[1], tmp.u8[2]);
456 ✗ FFSWAP(uint8_t, tmp.u8[3], tmp.u8[4]);
457 ✗ FFSWAP(uint8_t, tmp.u8[5], tmp.u8[6]);
458 }
459
460 60869 init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);
461 60869 err = ff_ac3_parse_header(&gbc, &hdr);
462
463
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 60869 if(err < 0)
464 52464 return 0;
465
466 8405 *new_frame_start = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
467
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 8405 *need_next_header = *new_frame_start || (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
468 8405 return hdr.frame_size;
469 }
470
471 84 static av_cold int ac3_parse_init(AVCodecParserContext *s1)
472 {
473 84 AACAC3ParseContext *s = s1->priv_data;
474 84 s->header_size = AC3_HEADER_SIZE;
475 84 s->crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
476 84 s->sync = ac3_sync;
477 84 return 0;
478 }
479
480
481 const FFCodecParser ff_ac3_parser = {
482 PARSER_CODEC_LIST(AV_CODEC_ID_AC3, AV_CODEC_ID_EAC3),
483 .priv_data_size = sizeof(AACAC3ParseContext),
484 .init = ac3_parse_init,
485 .parse = ff_aac_ac3_parse,
486 .close = ff_parse_close,
487 };
488
489 #else
490
491 int avpriv_ac3_parse_header(AC3HeaderInfo **phdr, const uint8_t *buf,
492 size_t size)
493 {
494 return AVERROR(ENOSYS);
495 }
496
497 int av_ac3_parse_header(const uint8_t *buf, size_t size,
498 uint8_t *bitstream_id, uint16_t *frame_size)
499 {
500 return AVERROR(ENOSYS);
501 }
502 #endif
503