libavcodec/ac3_parser.c

   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 int ff_ac3_find_syncword(const uint8_t *buf, int buf_size)
  58 {
  59     int i;
  60
  61     for (i = 1; i < buf_size; i += 2) {
  62         if (buf[i] == 0x77 || buf[i] == 0x0B) {
  63             if ((buf[i] ^ buf[i-1]) == (0x77 ^ 0x0B)) {
  64                 i--;
  65                 break;
  66             } else if ((buf[i] ^ buf[i+1]) == (0x77 ^ 0x0B)) {
  67                 break;
  68             }
  69         }
  70     }
  71     if (i >= buf_size)
  72         return AVERROR_INVALIDDATA;
  73
  74     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 static int ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
  83 {
  84     /* read the rest of the bsi. read twice for dual mono mode. */
  85     for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
  86         hdr->dialog_normalization[i] = -get_bits(gbc, 5);
  87         hdr->compression_exists[i] = get_bits1(gbc);
  88         if (hdr->compression_exists[i])
  89             hdr->heavy_dynamic_range[i] = get_bits(gbc, 8);
  90         if (get_bits1(gbc))
  91             skip_bits(gbc, 8); //skip language code
  92         if (get_bits1(gbc))
  93             skip_bits(gbc, 7); //skip audio production information
  94     }
  95
  96     skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
  97
  98     /* skip the timecodes or parse the Alternate Bit Stream Syntax */
  99     if (hdr->bitstream_id != 6) {
 100         if (get_bits1(gbc))
 101             skip_bits(gbc, 14); //skip timecode1
 102         if (get_bits1(gbc))
 103             skip_bits(gbc, 14); //skip timecode2
 104     } else {
 105         if (get_bits1(gbc)) {
 106             hdr->preferred_downmix       = get_bits(gbc, 2);
 107             hdr->center_mix_level_ltrt   = get_bits(gbc, 3);
 108             hdr->surround_mix_level_ltrt = av_clip(get_bits(gbc, 3), 3, 7);
 109             hdr->center_mix_level        = get_bits(gbc, 3);
 110             hdr->surround_mix_level      = av_clip(get_bits(gbc, 3), 3, 7);
 111         }
 112         if (get_bits1(gbc)) {
 113             hdr->dolby_surround_ex_mode = get_bits(gbc, 2);
 114             hdr->dolby_headphone_mode   = get_bits(gbc, 2);
 115             skip_bits(gbc, 10); // skip adconvtyp (1), xbsi2 (8), encinfo (1)
 116         }
 117     }
 118
 119     /* skip additional bitstream info */
 120     if (get_bits1(gbc)) {
 121         int i = get_bits(gbc, 6);
 122         do {
 123             skip_bits(gbc, 8);
 124         } while (i--);
 125     }
 126
 127     return 0;
 128 }
 129
 130 static int eac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
 131 {
 132     if (hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
 133         return AC3_PARSE_ERROR_FRAME_TYPE;
 134     if (hdr->substreamid)
 135         return AC3_PARSE_ERROR_FRAME_TYPE;
 136
 137     skip_bits(gbc, 5); // skip bitstream id
 138
 139     /* volume control params */
 140     for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
 141         hdr->dialog_normalization[i] = -get_bits(gbc, 5);
 142         hdr->compression_exists[i] = get_bits1(gbc);
 143         if (hdr->compression_exists[i])
 144             hdr->heavy_dynamic_range[i] = get_bits(gbc, 8);
 145     }
 146
 147     /* dependent stream channel map */
 148     if (hdr->frame_type == EAC3_FRAME_TYPE_DEPENDENT) {
 149         hdr->channel_map_present = get_bits1(gbc);
 150         if (hdr->channel_map_present) {
 151             int64_t channel_layout = 0;
 152             int channel_map = get_bits(gbc, 16);
 153
 154             for (int i = 0; i < 16; i++)
 155                 if (channel_map & (1 << (EAC3_MAX_CHANNELS - i - 1)))
 156                     channel_layout |= ff_eac3_custom_channel_map_locations[i][1];
 157
 158             if (av_popcount64(channel_layout) > EAC3_MAX_CHANNELS) {
 159                 return AC3_PARSE_ERROR_CHANNEL_MAP;
 160             }
 161             hdr->channel_map = channel_map;
 162         }
 163     }
 164
 165     /* mixing metadata */
 166     if (get_bits1(gbc)) {
 167         /* center and surround mix levels */
 168         if (hdr->channel_mode > AC3_CHMODE_STEREO) {
 169             hdr->preferred_downmix = get_bits(gbc, 2);
 170             if (hdr->channel_mode & 1) {
 171                 /* if three front channels exist */
 172                 hdr->center_mix_level_ltrt = get_bits(gbc, 3);
 173                 hdr->center_mix_level      = get_bits(gbc, 3);
 174             }
 175             if (hdr->channel_mode & 4) {
 176                 /* if a surround channel exists */
 177                 hdr->surround_mix_level_ltrt = av_clip(get_bits(gbc, 3), 3, 7);
 178                 hdr->surround_mix_level      = av_clip(get_bits(gbc, 3), 3, 7);
 179             }
 180         }
 181
 182         /* lfe mix level */
 183         if (hdr->lfe_on && (hdr->lfe_mix_level_exists = get_bits1(gbc))) {
 184             hdr->lfe_mix_level = get_bits(gbc, 5);
 185         }
 186
 187         /* info for mixing with other streams and substreams */
 188         if (hdr->frame_type == EAC3_FRAME_TYPE_INDEPENDENT) {
 189             for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
 190                 // TODO: apply program scale factor
 191                 if (get_bits1(gbc)) {
 192                     skip_bits(gbc, 6);  // skip program scale factor
 193                 }
 194             }
 195             if (get_bits1(gbc)) {
 196                 skip_bits(gbc, 6);  // skip external program scale factor
 197             }
 198             /* skip mixing parameter data */
 199             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             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             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     if (get_bits1(gbc)) {
 233         hdr->bitstream_mode = get_bits(gbc, 3);
 234         skip_bits(gbc, 2); // skip copyright bit and original bitstream bit
 235         if (hdr->channel_mode == AC3_CHMODE_STEREO) {
 236             hdr->dolby_surround_mode  = get_bits(gbc, 2);
 237             hdr->dolby_headphone_mode = get_bits(gbc, 2);
 238         }
 239         if (hdr->channel_mode >= AC3_CHMODE_2F2R) {
 240             hdr->dolby_surround_ex_mode = get_bits(gbc, 2);
 241         }
 242         for (int i = 0; i < (hdr->channel_mode ? 1 : 2); i++) {
 243             if (get_bits1(gbc)) {
 244                 skip_bits(gbc, 8); // skip mix level, room type, and A/D converter type
 245             }
 246         }
 247         if (hdr->sr_code != EAC3_SR_CODE_REDUCED) {
 248             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     if (hdr->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && hdr->num_blocks != 6) {
 257         skip_bits1(gbc); // skip converter synchronization flag
 258     }
 259
 260     /* original frame size code if this stream was converted from AC-3 */
 261     if (hdr->frame_type == EAC3_FRAME_TYPE_AC3_CONVERT &&
 262             (hdr->num_blocks == 6 || get_bits1(gbc))) {
 263         skip_bits(gbc, 6); // skip frame size code
 264     }
 265
 266     /* additional bitstream info */
 267     if (get_bits1(gbc)) {
 268         int addbsil = get_bits(gbc, 6);
 269         for (int i = 0; i < addbsil + 1; i++) {
 270             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                 skip_bits(gbc, 7);
 274                 hdr->eac3_extension_type_a = get_bits1(gbc);
 275                 if (hdr->eac3_extension_type_a) {
 276                     hdr->complexity_index_type_a = get_bits(gbc, 8);
 277                     i++;
 278                 }
 279             } else {
 280                 skip_bits(gbc, 8); // skip additional bit stream info
 281             }
 282         }
 283     }
 284
 285     return 0;
 286 }
 287
 288 int ff_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
 289 {
 290     int frame_size_code;
 291
 292     memset(hdr, 0, sizeof(*hdr));
 293
 294     hdr->sync_word = get_bits(gbc, 16);
 295     if(hdr->sync_word != 0x0B77)
 296         return AC3_PARSE_ERROR_SYNC;
 297
 298     /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
 299     hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F;
 300     if(hdr->bitstream_id > 16)
 301         return AC3_PARSE_ERROR_BSID;
 302
 303     hdr->num_blocks = 6;
 304     hdr->ac3_bit_rate_code = -1;
 305
 306     /* set default mix levels */
 307     hdr->center_mix_level   = 5;  // -4.5dB
 308     hdr->surround_mix_level = 6;  // -6.0dB
 309
 310     /* set default dolby surround mode */
 311     hdr->dolby_surround_mode = AC3_DSURMOD_NOTINDICATED;
 312
 313     if(hdr->bitstream_id <= 10) {
 314         /* Normal AC-3 */
 315         hdr->crc1 = get_bits(gbc, 16);
 316         hdr->sr_code = get_bits(gbc, 2);
 317         if(hdr->sr_code == 3)
 318             return AC3_PARSE_ERROR_SAMPLE_RATE;
 319
 320         frame_size_code = get_bits(gbc, 6);
 321         if(frame_size_code > 37)
 322             return AC3_PARSE_ERROR_FRAME_SIZE;
 323
 324         hdr->ac3_bit_rate_code = (frame_size_code >> 1);
 325
 326         skip_bits(gbc, 5); // skip bsid, already got it
 327
 328         hdr->bitstream_mode = get_bits(gbc, 3);
 329         hdr->channel_mode = get_bits(gbc, 3);
 330
 331         if(hdr->channel_mode == AC3_CHMODE_STEREO) {
 332             hdr->dolby_surround_mode = get_bits(gbc, 2);
 333         } else {
 334             if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)
 335                 hdr->  center_mix_level =   center_levels[get_bits(gbc, 2)];
 336             if(hdr->channel_mode & 4)
 337                 hdr->surround_mix_level = surround_levels[get_bits(gbc, 2)];
 338         }
 339         hdr->lfe_on = get_bits1(gbc);
 340
 341         hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
 342         hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
 343         hdr->bit_rate = (ff_ac3_bitrate_tab[hdr->ac3_bit_rate_code] * 1000) >> hdr->sr_shift;
 344         hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
 345         hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
 346         hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT;
 347         hdr->substreamid = 0;
 348
 349         int ret = ac3_parse_header(gbc, hdr);
 350         if (ret < 0)
 351             return ret;
 352     } else {
 353         /* Enhanced AC-3 */
 354         hdr->crc1 = 0;
 355         hdr->frame_type = get_bits(gbc, 2);
 356         if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
 357             return AC3_PARSE_ERROR_FRAME_TYPE;
 358
 359         hdr->substreamid = get_bits(gbc, 3);
 360
 361         hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;
 362         if(hdr->frame_size < AC3_HEADER_SIZE)
 363             return AC3_PARSE_ERROR_FRAME_SIZE;
 364
 365         hdr->sr_code = get_bits(gbc, 2);
 366         if (hdr->sr_code == 3) {
 367             int sr_code2 = get_bits(gbc, 2);
 368             if(sr_code2 == 3)
 369                 return AC3_PARSE_ERROR_SAMPLE_RATE;
 370             hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
 371             hdr->sr_shift = 1;
 372         } else {
 373             hdr->num_blocks = eac3_blocks[get_bits(gbc, 2)];
 374             hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
 375             hdr->sr_shift = 0;
 376         }
 377
 378         hdr->channel_mode = get_bits(gbc, 3);
 379         hdr->lfe_on = get_bits1(gbc);
 380
 381         hdr->bit_rate = 8LL * hdr->frame_size * hdr->sample_rate /
 382                         (hdr->num_blocks * 256);
 383         hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
 384
 385         int ret = eac3_parse_header(gbc, hdr);
 386         if (ret < 0)
 387             return ret;
 388     }
 389     hdr->channel_layout = ff_ac3_channel_layout_tab[hdr->channel_mode];
 390     if (hdr->lfe_on)
 391         hdr->channel_layout |= AV_CH_LOW_FREQUENCY;
 392
 393     return 0;
 394 }
 395
 396 // TODO: Better way to pass AC3HeaderInfo fields to mov muxer.
 397 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     if (!*phdr)
 405         *phdr = av_mallocz(sizeof(AC3HeaderInfo));
 406     if (!*phdr)
 407         return AVERROR(ENOMEM);
 408     hdr = *phdr;
 409
 410     err = init_get_bits8(&gb, buf, size);
 411     if (err < 0)
 412         return AVERROR_INVALIDDATA;
 413     err = ff_ac3_parse_header(&gb, hdr);
 414     if (err < 0)
 415         return AVERROR_INVALIDDATA;
 416
 417     return get_bits_count(&gb);
 418 }
 419
 420 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     size = FFMIN(32, size);
 429     memcpy(tmp, buf, size);
 430     memset(tmp + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
 431     err = init_get_bits8(&gb, tmp, size);
 432     if (err < 0)
 433         return AVERROR_INVALIDDATA;
 434     err = ff_ac3_parse_header(&gb, &hdr);
 435     if (err < 0)
 436         return AVERROR_INVALIDDATA;
 437
 438     *bitstream_id = hdr.bitstream_id;
 439     *frame_size   = hdr.frame_size;
 440
 441     return 0;
 442 }
 443
 444 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     } tmp = { av_be2ne64(state) };
 451     AC3HeaderInfo hdr;
 452     GetBitContext gbc;
 453
 454     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     init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);
 461     err = ff_ac3_parse_header(&gbc, &hdr);
 462
 463     if(err < 0)
 464         return 0;
 465
 466     *new_frame_start  = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
 467     *need_next_header = *new_frame_start || (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
 468     return hdr.frame_size;
 469 }
 470
 471 static av_cold int ac3_parse_init(AVCodecParserContext *s1)
 472 {
 473     AACAC3ParseContext *s = s1->priv_data;
 474     s->header_size = AC3_HEADER_SIZE;
 475     s->crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
 476     s->sync = ac3_sync;
 477     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