libavformat/mp3dec.c

   1 /*
   2  * MP3 demuxer
   3  * Copyright (c) 2003 Fabrice Bellard
   4  *
   5  * This file is part of Libav.
   6  *
   7  * Libav 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.
  11  *
  12  * Libav 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.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with Libav; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include "libavutil/avstring.h"
  23 #include "libavutil/intreadwrite.h"
  24 #include "libavutil/crc.h"
  25 #include "libavutil/dict.h"
  26 #include "libavutil/mathematics.h"
  27 #include "avformat.h"
  28 #include "internal.h"
  29 #include "avio_internal.h"
  30 #include "id3v2.h"
  31 #include "id3v1.h"
  32 #include "replaygain.h"
  33
  34 #include "libavcodec/avcodec.h"
  35 #include "libavcodec/mpegaudiodecheader.h"
  36
  37 #define XING_FLAG_FRAMES 0x01
  38 #define XING_FLAG_SIZE   0x02
  39 #define XING_FLAG_TOC    0x04
  40 #define XING_FLAC_QSCALE 0x08
  41
  42 #define XING_TOC_COUNT 100
  43
  44 typedef struct MP3DecContext {
  45     int xing_toc;
  46     unsigned frames; /* Total number of frames in file */
  47     unsigned size;   /* Total number of bytes in the stream */
  48     int is_cbr;
  49 } MP3DecContext;
  50
  51 /* mp3 read */
  52
  53 static int mp3_read_probe(AVProbeData *p)
  54 {
  55     int max_frames, first_frames = 0;
  56     int fsize, frames, sample_rate;
  57     uint32_t header;
  58     uint8_t *buf, *buf0, *buf2, *end;
  59     AVCodecContext *avctx = avcodec_alloc_context3(NULL);
  60
  61     if (!avctx)
  62         return AVERROR(ENOMEM);
  63
  64     buf0 = p->buf;
  65     end = p->buf + p->buf_size - sizeof(uint32_t);
  66     while(buf0 < end && !*buf0)
  67         buf0++;
  68
  69     max_frames = 0;
  70     buf = buf0;
  71
  72     for(; buf < end; buf= buf2+1) {
  73         buf2 = buf;
  74
  75         for(frames = 0; buf2 < end; frames++) {
  76             header = AV_RB32(buf2);
  77             fsize = avpriv_mpa_decode_header(avctx, header, &sample_rate,
  78                                              &sample_rate, &sample_rate,
  79                                              &sample_rate);
  80             if(fsize < 0)
  81                 break;
  82             buf2 += fsize;
  83         }
  84         max_frames = FFMAX(max_frames, frames);
  85         if(buf == buf0)
  86             first_frames= frames;
  87     }
  88     avcodec_free_context(&avctx);
  89     // keep this in sync with ac3 probe, both need to avoid
  90     // issues with MPEG-files!
  91     if (first_frames >= 10)
  92         return AVPROBE_SCORE_EXTENSION + 5;
  93     if (first_frames >= 4)
  94         return AVPROBE_SCORE_EXTENSION + 1;
  95
  96     if (max_frames) {
  97         int pes = 0, i;
  98         unsigned int code = -1;
  99
 100 #define VIDEO_ID 0x000001e0
 101 #define AUDIO_ID 0x000001c0
 102         /* do a search for mpegps headers to be able to properly bias
 103          * towards mpegps if we detect this stream as both. */
 104         for (i = 0; i<p->buf_size; i++) {
 105             code = (code << 8) + p->buf[i];
 106             if ((code & 0xffffff00) == 0x100) {
 107                 if     ((code & 0x1f0) == VIDEO_ID) pes++;
 108                 else if((code & 0x1e0) == AUDIO_ID) pes++;
 109             }
 110         }
 111
 112         if (pes)
 113             max_frames = (max_frames + pes - 1) / pes;
 114     }
 115     if      (max_frames >  500) return AVPROBE_SCORE_EXTENSION;
 116     else if (max_frames >= 4)   return AVPROBE_SCORE_EXTENSION / 2;
 117     else if (max_frames >= 1)   return 1;
 118     else                        return 0;
 119 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
 120 }
 121
 122 static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
 123 {
 124     int i;
 125     MP3DecContext *mp3 = s->priv_data;
 126
 127     if (!filesize &&
 128         !(filesize = avio_size(s->pb))) {
 129         av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
 130         return;
 131     }
 132
 133     for (i = 0; i < XING_TOC_COUNT; i++) {
 134         uint8_t b = avio_r8(s->pb);
 135
 136         av_add_index_entry(s->streams[0],
 137                            av_rescale(b, filesize, 256),
 138                            av_rescale(i, duration, XING_TOC_COUNT),
 139                            0, 0, AVINDEX_KEYFRAME);
 140     }
 141     mp3->xing_toc = 1;
 142 }
 143
 144 static void mp3_parse_info_tag(AVFormatContext *s, AVStream *st,
 145                                MPADecodeHeader *c, uint32_t spf)
 146 {
 147 #define LAST_BITS(k, n) ((k) & ((1 << (n)) - 1))
 148 #define MIDDLE_BITS(k, m, n) LAST_BITS((k) >> (m), ((n) - (m)))
 149
 150     uint16_t crc;
 151     uint32_t v;
 152
 153     char version[10];
 154
 155     uint32_t peak   = 0;
 156     int32_t  r_gain = INT32_MIN, a_gain = INT32_MIN;
 157
 158     MP3DecContext *mp3 = s->priv_data;
 159     const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
 160
 161     /* Check for Xing / Info tag */
 162     avio_skip(s->pb, xing_offtbl[c->lsf == 1][c->nb_channels == 1]);
 163     v = avio_rb32(s->pb);
 164     mp3->is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
 165     if (v != MKBETAG('X', 'i', 'n', 'g') && !mp3->is_cbr)
 166         return;
 167
 168     v = avio_rb32(s->pb);
 169     if (v & XING_FLAG_FRAMES)
 170         mp3->frames = avio_rb32(s->pb);
 171     if (v & XING_FLAG_SIZE)
 172         mp3->size = avio_rb32(s->pb);
 173     if (v & XING_FLAG_TOC && mp3->frames)
 174         read_xing_toc(s, mp3->size, av_rescale_q(mp3->frames,
 175                                        (AVRational){spf, c->sample_rate},
 176                                        st->time_base));
 177
 178     /* VBR quality */
 179     if (v & XING_FLAC_QSCALE)
 180         avio_rb32(s->pb);
 181
 182     /* Encoder short version string */
 183     memset(version, 0, sizeof(version));
 184     avio_read(s->pb, version, 9);
 185
 186     /* Info Tag revision + VBR method */
 187     avio_r8(s->pb);
 188
 189     /* Lowpass filter value */
 190     avio_r8(s->pb);
 191
 192     /* ReplayGain peak */
 193     v    = avio_rb32(s->pb);
 194     peak = av_rescale(v, 100000, 1 << 23);
 195
 196     /* Radio ReplayGain */
 197     v = avio_rb16(s->pb);
 198
 199     if (MIDDLE_BITS(v, 13, 15) == 1) {
 200         r_gain = MIDDLE_BITS(v, 0, 8) * 10000;
 201
 202         if (v & (1 << 9))
 203             r_gain *= -1;
 204     }
 205
 206     /* Audiophile ReplayGain */
 207     v = avio_rb16(s->pb);
 208
 209     if (MIDDLE_BITS(v, 13, 15) == 2) {
 210         a_gain = MIDDLE_BITS(v, 0, 8) * 10000;
 211
 212         if (v & (1 << 9))
 213             a_gain *= -1;
 214     }
 215
 216     /* Encoding flags + ATH Type */
 217     avio_r8(s->pb);
 218
 219     /* if ABR {specified bitrate} else {minimal bitrate} */
 220     avio_r8(s->pb);
 221
 222     /* Encoder delays */
 223     avio_rb24(s->pb);
 224
 225     /* Misc */
 226     avio_r8(s->pb);
 227
 228     /* MP3 gain */
 229     avio_r8(s->pb);
 230
 231     /* Preset and surround info */
 232     avio_rb16(s->pb);
 233
 234     /* Music length */
 235     avio_rb32(s->pb);
 236
 237     /* Music CRC */
 238     avio_rb16(s->pb);
 239
 240     /* Info Tag CRC */
 241     crc = ffio_get_checksum(s->pb);
 242     v   = avio_rb16(s->pb);
 243
 244     if (v == crc) {
 245         ff_replaygain_export_raw(st, r_gain, peak, a_gain, 0);
 246         av_dict_set(&st->metadata, "encoder", version, 0);
 247     }
 248 }
 249
 250 static void mp3_parse_vbri_tag(AVFormatContext *s, AVStream *st, int64_t base)
 251 {
 252     uint32_t v;
 253     MP3DecContext *mp3 = s->priv_data;
 254
 255     /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
 256     avio_seek(s->pb, base + 4 + 32, SEEK_SET);
 257     v = avio_rb32(s->pb);
 258     if (v == MKBETAG('V', 'B', 'R', 'I')) {
 259         /* Check tag version */
 260         if (avio_rb16(s->pb) == 1) {
 261             /* skip delay and quality */
 262             avio_skip(s->pb, 4);
 263             mp3->size = avio_rb32(s->pb);
 264             mp3->frames = avio_rb32(s->pb);
 265         }
 266     }
 267 }
 268
 269 /**
 270  * Try to find Xing/Info/VBRI tags and compute duration from info therein
 271  */
 272 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
 273 {
 274     uint32_t v, spf;
 275     MPADecodeHeader c;
 276     int vbrtag_size = 0;
 277     MP3DecContext *mp3 = s->priv_data;
 278
 279     ffio_init_checksum(s->pb, ff_crcA001_update, 0);
 280
 281     v = avio_rb32(s->pb);
 282     if(ff_mpa_check_header(v) < 0)
 283       return -1;
 284
 285     if (avpriv_mpegaudio_decode_header(&c, v) == 0)
 286         vbrtag_size = c.frame_size;
 287     if(c.layer != 3)
 288         return -1;
 289
 290     spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
 291
 292     mp3->frames = 0;
 293     mp3->size   = 0;
 294
 295     mp3_parse_info_tag(s, st, &c, spf);
 296     mp3_parse_vbri_tag(s, st, base);
 297
 298     if (!mp3->frames && !mp3->size)
 299         return -1;
 300
 301     /* Skip the vbr tag frame */
 302     avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
 303
 304     if (mp3->frames)
 305         st->duration = av_rescale_q(mp3->frames, (AVRational){spf, c.sample_rate},
 306                                     st->time_base);
 307     if (mp3->size && mp3->frames && !mp3->is_cbr)
 308         st->codec->bit_rate = av_rescale(mp3->size, 8 * c.sample_rate, mp3->frames * (int64_t)spf);
 309
 310     return 0;
 311 }
 312
 313 static int mp3_read_header(AVFormatContext *s)
 314 {
 315     AVStream *st;
 316     int64_t off;
 317     int ret;
 318
 319     st = avformat_new_stream(s, NULL);
 320     if (!st)
 321         return AVERROR(ENOMEM);
 322
 323     st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
 324     st->codec->codec_id = AV_CODEC_ID_MP3;
 325     st->need_parsing = AVSTREAM_PARSE_FULL;
 326     st->start_time = 0;
 327
 328     // lcm of all mp3 sample rates
 329     avpriv_set_pts_info(st, 64, 1, 14112000);
 330
 331     off = avio_tell(s->pb);
 332
 333     if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
 334         ff_id3v1_read(s);
 335
 336     if (mp3_parse_vbr_tags(s, st, off) < 0)
 337         avio_seek(s->pb, off, SEEK_SET);
 338
 339     ret = ff_replaygain_export(st, s->metadata);
 340     if (ret < 0)
 341         return ret;
 342
 343     /* the parameters will be extracted from the compressed bitstream */
 344     return 0;
 345 }
 346
 347 #define MP3_PACKET_SIZE 1024
 348
 349 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
 350 {
 351     int ret;
 352
 353     ret = av_get_packet(s->pb, pkt, MP3_PACKET_SIZE);
 354     if (ret < 0)
 355         return ret;
 356
 357     pkt->stream_index = 0;
 358
 359     if (ret > ID3v1_TAG_SIZE &&
 360         memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
 361         ret -= ID3v1_TAG_SIZE;
 362
 363     /* note: we need to modify the packet size here to handle the last
 364        packet */
 365     pkt->size = ret;
 366     return ret;
 367 }
 368
 369 #define SEEK_PACKETS 4
 370 #define SEEK_WINDOW (SEEK_PACKETS * MP3_PACKET_SIZE)
 371
 372 /* The toc entry can position to the wrong byte offset, try to pick
 373  * the closest frame by probing the data in a window of 4 packets.
 374  */
 375
 376 static int check(AVIOContext *pb, int64_t pos, int64_t *out_pos)
 377 {
 378     MPADecodeHeader mh = { 0 };
 379     int i;
 380     uint32_t header;
 381     int64_t off = 0;
 382
 383
 384     for (i = 0; i < SEEK_PACKETS; i++) {
 385         off = avio_seek(pb, pos + mh.frame_size, SEEK_SET);
 386         if (off < 0)
 387             break;
 388
 389         header = avio_rb32(pb);
 390
 391         if (ff_mpa_check_header(header) < 0 ||
 392             avpriv_mpegaudio_decode_header(&mh, header))
 393             break;
 394         out_pos[i] = off;
 395     }
 396
 397     return i;
 398 }
 399
 400 static int reposition(AVFormatContext *s, int64_t pos)
 401 {
 402     int ret, best_valid = -1;
 403     int64_t p, best_pos = -1;
 404
 405     for (p = FFMAX(pos - SEEK_WINDOW / 2, 0); p < pos + SEEK_WINDOW / 2; p++) {
 406         int64_t out_pos[SEEK_PACKETS];
 407         ret = check(s->pb, p, out_pos);
 408
 409         if (best_valid < ret) {
 410             int i;
 411             for (i = 0; i < ret; i++) {
 412                 if (llabs(best_pos - pos) > llabs(out_pos[i] - pos)) {
 413                     best_pos   = out_pos[i];
 414                     best_valid = ret;
 415                 }
 416             }
 417             if (best_pos == pos && best_valid == SEEK_PACKETS)
 418                 break;
 419         }
 420     }
 421
 422     if (best_valid <= 0)
 423         return AVERROR(ENOSYS);
 424
 425     p = avio_seek(s->pb, best_pos, SEEK_SET);
 426     if (p < 0)
 427         return p;
 428
 429     return 0;
 430 }
 431
 432 static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
 433                     int flags)
 434 {
 435     MP3DecContext *mp3 = s->priv_data;
 436     AVIndexEntry *ie;
 437     AVStream *st = s->streams[0];
 438     int64_t ret  = av_index_search_timestamp(st, timestamp, flags);
 439
 440     if (!mp3->xing_toc)
 441         return AVERROR(ENOSYS);
 442
 443     if (ret < 0)
 444         return ret;
 445
 446     ie = &st->index_entries[ret];
 447
 448     ret = reposition(s, ie->pos);
 449     if (ret < 0)
 450         return ret;
 451
 452     ff_update_cur_dts(s, st, ie->timestamp);
 453
 454     return 0;
 455 }
 456
 457 AVInputFormat ff_mp3_demuxer = {
 458     .name           = "mp3",
 459     .long_name      = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
 460     .read_probe     = mp3_read_probe,
 461     .read_header    = mp3_read_header,
 462     .read_packet    = mp3_read_packet,
 463     .read_seek      = mp3_seek,
 464     .priv_data_size = sizeof(MP3DecContext),
 465     .flags          = AVFMT_GENERIC_INDEX,
 466     .extensions     = "mp2,mp3,m2a,mpa", /* XXX: use probe */
 467 };