FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/ac3_parser.c
Date: 2025-07-28 20:30:09
Exec Total Coverage
Lines: 216 243 88.9%
Functions: 8 8 100.0%
Branches: 145 184 78.8%
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
35
36 #define AC3_HEADER_SIZE 7
37
38 #if CONFIG_AC3_PARSER
39
40 static const uint8_t eac3_blocks[4] = {
41 1, 2, 3, 6
42 };
43
44 /**
45 * Table for center mix levels
46 * reference: Section 5.4.2.4 cmixlev
47 */
48 static const uint8_t center_levels[4] = { 4, 5, 6, 5 };
49
50 /**
51 * Table for surround mix levels
52 * reference: Section 5.4.2.5 surmixlev
53 */
54 static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };
55
56 8527 int ff_ac3_find_syncword(const uint8_t *buf, int buf_size)
57 {
58 int i;
59
60
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 9935 for (i = 1; i < buf_size; i += 2) {
61
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 9924 if (buf[i] == 0x77 || buf[i] == 0x0B) {
62
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 8524 if ((buf[i] ^ buf[i-1]) == (0x77 ^ 0x0B)) {
63 8516 i--;
64 8516 break;
65
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 8 } else if ((buf[i] ^ buf[i+1]) == (0x77 ^ 0x0B)) {
66 ✗ break;
67 }
68 }
69 }
70
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 8527 if (i >= buf_size)
71 11 return AVERROR_INVALIDDATA;
72
73 8516 return i;
74 }
75
76 /**
77 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
78 * GetBitContext within AC3DecodeContext must point to
79 * the start of the synchronized AC-3 bitstream.
80 */
81 14922 static int ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
82 {
83 /* read the rest of the bsi. read twice for dual mono mode. */
84
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 35432 for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
85 20510 hdr->dialog_normalization[i] = -get_bits(gbc, 5);
86 20510 hdr->compression_exists[i] = get_bits1(gbc);
87
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 20510 if (hdr->compression_exists[i])
88 7693 hdr->heavy_dynamic_range[i] = get_bits(gbc, 8);
89
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 20510 if (get_bits1(gbc))
90 922 skip_bits(gbc, 8); //skip language code
91
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 20510 if (get_bits1(gbc))
92 5431 skip_bits(gbc, 7); //skip audio production information
93 }
94
95 14922 skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
96
97 /* skip the timecodes or parse the Alternate Bit Stream Syntax */
98
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 14922 if (hdr->bitstream_id != 6) {
99
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 13392 if (get_bits1(gbc))
100 1720 skip_bits(gbc, 14); //skip timecode1
101
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 13392 if (get_bits1(gbc))
102 1518 skip_bits(gbc, 14); //skip timecode2
103 } else {
104
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 1530 if (get_bits1(gbc)) {
105 844 hdr->preferred_downmix = get_bits(gbc, 2);
106 844 hdr->center_mix_level_ltrt = get_bits(gbc, 3);
107 844 hdr->surround_mix_level_ltrt = av_clip(get_bits(gbc, 3), 3, 7);
108 844 hdr->center_mix_level = get_bits(gbc, 3);
109 844 hdr->surround_mix_level = av_clip(get_bits(gbc, 3), 3, 7);
110 }
111
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 1530 if (get_bits1(gbc)) {
112 830 hdr->dolby_surround_ex_mode = get_bits(gbc, 2);
113 830 hdr->dolby_headphone_mode = get_bits(gbc, 2);
114 830 skip_bits(gbc, 10); // skip adconvtyp (1), xbsi2 (8), encinfo (1)
115 }
116 }
117
118 /* skip additional bitstream info */
119
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 14922 if (get_bits1(gbc)) {
120 1680 int i = get_bits(gbc, 6);
121 do {
122 45514 skip_bits(gbc, 8);
123
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 45514 } while (i--);
124 }
125
126 14922 return 0;
127 }
128
129 109966 static int eac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
130 {
131
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 109966 if (hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
132 ✗ return AC3_PARSE_ERROR_FRAME_TYPE;
133
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 109966 if (hdr->substreamid)
134 8880 return AC3_PARSE_ERROR_FRAME_TYPE;
135
136 101086 skip_bits(gbc, 5); // skip bitstream id
137
138 /* volume control params */
139
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 203238 for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
140 102152 hdr->dialog_normalization[i] = -get_bits(gbc, 5);
141 102152 hdr->compression_exists[i] = get_bits1(gbc);
142
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 102152 if (hdr->compression_exists[i])
143 100097 hdr->heavy_dynamic_range[i] = get_bits(gbc, 8);
144 }
145
146 /* dependent stream channel map */
147
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 101086 if (hdr->frame_type == EAC3_FRAME_TYPE_DEPENDENT) {
148 1058 hdr->channel_map_present = get_bits1(gbc);
149
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 1058 if (hdr->channel_map_present) {
150 744 int64_t channel_layout = 0;
151 744 int channel_map = get_bits(gbc, 16);
152
153
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 12648 for (int i = 0; i < 16; i++)
154
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 11904 if (channel_map & (1 << (EAC3_MAX_CHANNELS - i - 1)))
155 2242 channel_layout |= ff_eac3_custom_channel_map_locations[i][1];
156
157
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 744 if (av_popcount64(channel_layout) > EAC3_MAX_CHANNELS) {
158 ✗ return AC3_PARSE_ERROR_CHANNEL_MAP;
159 }
160 744 hdr->channel_map = channel_map;
161 }
162 }
163
164 /* mixing metadata */
165
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 101086 if (get_bits1(gbc)) {
166 /* center and surround mix levels */
167
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 93528 if (hdr->channel_mode > AC3_CHMODE_STEREO) {
168 488 hdr->preferred_downmix = get_bits(gbc, 2);
169
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 488 if (hdr->channel_mode & 1) {
170 /* if three front channels exist */
171 488 hdr->center_mix_level_ltrt = get_bits(gbc, 3);
172 488 hdr->center_mix_level = get_bits(gbc, 3);
173 }
174
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 488 if (hdr->channel_mode & 4) {
175 /* if a surround channel exists */
176 488 hdr->surround_mix_level_ltrt = av_clip(get_bits(gbc, 3), 3, 7);
177 488 hdr->surround_mix_level = av_clip(get_bits(gbc, 3), 3, 7);
178 }
179 }
180
181 /* lfe mix level */
182
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 93528 if (hdr->lfe_on && (hdr->lfe_mix_level_exists = get_bits1(gbc))) {
183 484 hdr->lfe_mix_level = get_bits(gbc, 5);
184 }
185
186 /* info for mixing with other streams and substreams */
187
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 93528 if (hdr->frame_type == EAC3_FRAME_TYPE_INDEPENDENT) {
188
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 187048 for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
189 // TODO: apply program scale factor
190
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 93524 if (get_bits1(gbc)) {
191 ✗ skip_bits(gbc, 6); // skip program scale factor
192 }
193 }
194
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 93524 if (get_bits1(gbc)) {
195 ✗ skip_bits(gbc, 6); // skip external program scale factor
196 }
197 /* skip mixing parameter data */
198
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 93524 switch(get_bits(gbc, 2)) {
199 ✗ case 1: skip_bits(gbc, 5); break;
200 ✗ case 2: skip_bits(gbc, 12); break;
201 ✗ case 3: {
202 ✗ int mix_data_size = (get_bits(gbc, 5) + 2) << 3;
203 ✗ skip_bits_long(gbc, mix_data_size);
204 ✗ break;
205 }
206 }
207 /* skip pan information for mono or dual mono source */
208
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 93524 if (hdr->channel_mode < AC3_CHMODE_STEREO) {
209 ✗ for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
210 ✗ if (get_bits1(gbc)) {
211 /* note: this is not in the ATSC A/52B specification
212 reference: ETSI TS 102 366 V1.1.1
213 section: E.1.3.1.25 */
214 ✗ skip_bits(gbc, 8); // skip pan mean direction index
215 ✗ skip_bits(gbc, 6); // skip reserved paninfo bits
216 }
217 }
218 }
219 /* skip mixing configuration information */
220
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 93524 if (get_bits1(gbc)) {
221 ✗ for (int i = 0; i < hdr->num_blocks; i++) {
222 ✗ if (hdr->num_blocks == 1 || get_bits1(gbc)) {
223 ✗ skip_bits(gbc, 5);
224 }
225 }
226 }
227 }
228 }
229
230 /* informational metadata */
231
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 101086 if (get_bits1(gbc)) {
232 93812 hdr->bitstream_mode = get_bits(gbc, 3);
233 93812 skip_bits(gbc, 2); // skip copyright bit and original bitstream bit
234
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 93812 if (hdr->channel_mode == AC3_CHMODE_STEREO) {
235 93324 hdr->dolby_surround_mode = get_bits(gbc, 2);
236 93324 hdr->dolby_headphone_mode = get_bits(gbc, 2);
237 }
238
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 93812 if (hdr->channel_mode >= AC3_CHMODE_2F2R) {
239 488 hdr->dolby_surround_ex_mode = get_bits(gbc, 2);
240 }
241
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 187624 for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
242
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 93812 if (get_bits1(gbc)) {
243 93812 skip_bits(gbc, 8); // skip mix level, room type, and A/D converter type
244 }
245 }
246
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 93812 if (hdr->sr_code != EAC3_SR_CODE_REDUCED) {
247 93812 skip_bits1(gbc); // skip source sample rate code
248 }
249 }
250
251 /* converter synchronization flag
252 If frames are less than six blocks, this bit should be turned on
253 once every 6 blocks to indicate the start of a frame set.
254 reference: RFC 4598, Section 2.1.3 Frame Sets */
255
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 101086 if (hdr->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && hdr->num_blocks != 6) {
256 1501 skip_bits1(gbc); // skip converter synchronization flag
257 }
258
259 /* original frame size code if this stream was converted from AC-3 */
260
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 101086 if (hdr->frame_type == EAC3_FRAME_TYPE_AC3_CONVERT &&
261
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 4 (hdr->num_blocks == 6 || get_bits1(gbc))) {
262 ✗ skip_bits(gbc, 6); // skip frame size code
263 }
264
265 /* additional bitstream info */
266
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 101086 if (get_bits1(gbc)) {
267 742 int addbsil = get_bits(gbc, 6);
268
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 1484 for (int i = 0; i < addbsil + 1; i++) {
269
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 742 if (i == 0) {
270 /* In this 8 bit chunk, the LSB is equal to flag_ec3_extension_type_a
271 which can be used to detect Atmos presence */
272 742 skip_bits(gbc, 7);
273 742 hdr->eac3_extension_type_a = get_bits1(gbc);
274
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 742 if (hdr->eac3_extension_type_a) {
275 742 hdr->complexity_index_type_a = get_bits(gbc, 8);
276 742 i++;
277 }
278 } else {
279 ✗ skip_bits(gbc, 8); // skip additional bit stream info
280 }
281 }
282 }
283
284 101086 return 0;
285 }
286
287 190842 int ff_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
288 {
289 int frame_size_code;
290
291 190842 memset(hdr, 0, sizeof(*hdr));
292
293 190842 hdr->sync_word = get_bits(gbc, 16);
294
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 190842 if(hdr->sync_word != 0x0B77)
295 55666 return AC3_PARSE_ERROR_SYNC;
296
297 /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
298 135176 hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F;
299
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 135176 if(hdr->bitstream_id > 16)
300 8188 return AC3_PARSE_ERROR_BSID;
301
302 126988 hdr->num_blocks = 6;
303 126988 hdr->ac3_bit_rate_code = -1;
304
305 /* set default mix levels */
306 126988 hdr->center_mix_level = 5; // -4.5dB
307 126988 hdr->surround_mix_level = 6; // -6.0dB
308
309 /* set default dolby surround mode */
310 126988 hdr->dolby_surround_mode = AC3_DSURMOD_NOTINDICATED;
311
312
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 126988 if(hdr->bitstream_id <= 10) {
313 /* Normal AC-3 */
314 16714 hdr->crc1 = get_bits(gbc, 16);
315 16714 hdr->sr_code = get_bits(gbc, 2);
316
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 16714 if(hdr->sr_code == 3)
317 540 return AC3_PARSE_ERROR_SAMPLE_RATE;
318
319 16174 frame_size_code = get_bits(gbc, 6);
320
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 16174 if(frame_size_code > 37)
321 1252 return AC3_PARSE_ERROR_FRAME_SIZE;
322
323 14922 hdr->ac3_bit_rate_code = (frame_size_code >> 1);
324
325 14922 skip_bits(gbc, 5); // skip bsid, already got it
326
327 14922 hdr->bitstream_mode = get_bits(gbc, 3);
328 14922 hdr->channel_mode = get_bits(gbc, 3);
329
330
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 14922 if(hdr->channel_mode == AC3_CHMODE_STEREO) {
331 2410 hdr->dolby_surround_mode = get_bits(gbc, 2);
332 } else {
333
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 12512 if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)
334 6065 hdr-> center_mix_level = center_levels[get_bits(gbc, 2)];
335
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 12512 if(hdr->channel_mode & 4)
336 6109 hdr->surround_mix_level = surround_levels[get_bits(gbc, 2)];
337 }
338 14922 hdr->lfe_on = get_bits1(gbc);
339
340 14922 hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
341 14922 hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
342 14922 hdr->bit_rate = (ff_ac3_bitrate_tab[hdr->ac3_bit_rate_code] * 1000) >> hdr->sr_shift;
343 14922 hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
344 14922 hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
345 14922 hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT;
346 14922 hdr->substreamid = 0;
347
348 14922 int ret = ac3_parse_header(gbc, hdr);
349
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 14922 if (ret < 0)
350 ✗ return ret;
351 } else {
352 /* Enhanced AC-3 */
353 110274 hdr->crc1 = 0;
354 110274 hdr->frame_type = get_bits(gbc, 2);
355
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 110274 if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
356 288 return AC3_PARSE_ERROR_FRAME_TYPE;
357
358 109986 hdr->substreamid = get_bits(gbc, 3);
359
360 109986 hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;
361
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 109986 if(hdr->frame_size < AC3_HEADER_SIZE)
362 2 return AC3_PARSE_ERROR_FRAME_SIZE;
363
364 109984 hdr->sr_code = get_bits(gbc, 2);
365
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 109984 if (hdr->sr_code == 3) {
366 84 int sr_code2 = get_bits(gbc, 2);
367
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 84 if(sr_code2 == 3)
368 18 return AC3_PARSE_ERROR_SAMPLE_RATE;
369 66 hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
370 66 hdr->sr_shift = 1;
371 } else {
372 109900 hdr->num_blocks = eac3_blocks[get_bits(gbc, 2)];
373 109900 hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
374 109900 hdr->sr_shift = 0;
375 }
376
377 109966 hdr->channel_mode = get_bits(gbc, 3);
378 109966 hdr->lfe_on = get_bits1(gbc);
379
380 109966 hdr->bit_rate = 8LL * hdr->frame_size * hdr->sample_rate /
381 109966 (hdr->num_blocks * 256);
382 109966 hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
383
384 109966 int ret = eac3_parse_header(gbc, hdr);
385
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 109966 if (ret < 0)
386 8880 return ret;
387 }
388 116008 hdr->channel_layout = ff_ac3_channel_layout_tab[hdr->channel_mode];
389
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 116008 if (hdr->lfe_on)
390 8139 hdr->channel_layout |= AV_CH_LOW_FREQUENCY;
391
392 116008 return 0;
393 }
394
395 // TODO: Better way to pass AC3HeaderInfo fields to mov muxer.
396 7553 int avpriv_ac3_parse_header(AC3HeaderInfo **phdr, const uint8_t *buf,
397 size_t size)
398 {
399 GetBitContext gb;
400 AC3HeaderInfo *hdr;
401 int err;
402
403
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 7553 if (!*phdr)
404 1039 *phdr = av_mallocz(sizeof(AC3HeaderInfo));
405
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 7553 if (!*phdr)
406 ✗ return AVERROR(ENOMEM);
407 7553 hdr = *phdr;
408
409 7553 err = init_get_bits8(&gb, buf, size);
410
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 7553 if (err < 0)
411 ✗ return AVERROR_INVALIDDATA;
412 7553 err = ff_ac3_parse_header(&gb, hdr);
413
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 7553 if (err < 0)
414 2 return AVERROR_INVALIDDATA;
415
416 7551 return get_bits_count(&gb);
417 }
418
419 132832 int av_ac3_parse_header(const uint8_t *buf, size_t size,
420 uint8_t *bitstream_id, uint16_t *frame_size)
421 {
422 GetBitContext gb;
423 AC3HeaderInfo hdr;
424 uint8_t tmp[32 + AV_INPUT_BUFFER_PADDING_SIZE];
425 int err;
426
427 132832 size = FFMIN(32, size);
428 132832 memcpy(tmp, buf, size);
429 132832 memset(tmp + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
430 132832 err = init_get_bits8(&gb, tmp, size);
431
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 132832 if (err < 0)
432 ✗ return AVERROR_INVALIDDATA;
433 132832 err = ff_ac3_parse_header(&gb, &hdr);
434
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 132832 if (err < 0)
435 33684 return AVERROR_INVALIDDATA;
436
437 99148 *bitstream_id = hdr.bitstream_id;
438 99148 *frame_size = hdr.frame_size;
439
440 99148 return 0;
441 }
442
443 47667 static int ac3_sync(uint64_t state, int *need_next_header, int *new_frame_start)
444 {
445 int err;
446 union {
447 uint64_t u64;
448 uint8_t u8[8 + AV_INPUT_BUFFER_PADDING_SIZE];
449 47667 } tmp = { av_be2ne64(state) };
450 AC3HeaderInfo hdr;
451 GetBitContext gbc;
452
453
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 47667 if (tmp.u8[1] == 0x77 && tmp.u8[2] == 0x0b) {
454 ✗ FFSWAP(uint8_t, tmp.u8[1], tmp.u8[2]);
455 ✗ FFSWAP(uint8_t, tmp.u8[3], tmp.u8[4]);
456 ✗ FFSWAP(uint8_t, tmp.u8[5], tmp.u8[6]);
457 }
458
459 47667 init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);
460 47667 err = ff_ac3_parse_header(&gbc, &hdr);
461
462
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 47667 if(err < 0)
463 41148 return 0;
464
465 6519 *new_frame_start = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
466
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 6519 *need_next_header = *new_frame_start || (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
467 6519 return hdr.frame_size;
468 }
469
470 77 static av_cold int ac3_parse_init(AVCodecParserContext *s1)
471 {
472 77 AACAC3ParseContext *s = s1->priv_data;
473 77 s->header_size = AC3_HEADER_SIZE;
474 77 s->crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
475 77 s->sync = ac3_sync;
476 77 return 0;
477 }
478
479
480 const AVCodecParser ff_ac3_parser = {
481 .codec_ids = { AV_CODEC_ID_AC3, AV_CODEC_ID_EAC3 },
482 .priv_data_size = sizeof(AACAC3ParseContext),
483 .parser_init = ac3_parse_init,
484 .parser_parse = ff_aac_ac3_parse,
485 .parser_close = ff_parse_close,
486 };
487
488 #else
489
490 int avpriv_ac3_parse_header(AC3HeaderInfo **phdr, const uint8_t *buf,
491 size_t size)
492 {
493 return AVERROR(ENOSYS);
494 }
495
496 int av_ac3_parse_header(const uint8_t *buf, size_t size,
497 uint8_t *bitstream_id, uint16_t *frame_size)
498 {
499 return AVERROR(ENOSYS);
500 }
501 #endif
502