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mp3dec.c
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1 /*
2  * MP3 demuxer
3  * Copyright (c) 2003 Fabrice Bellard
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg 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  * FFmpeg 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 FFmpeg; 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/opt.h"
23 #include "libavutil/avstring.h"
24 #include "libavutil/intreadwrite.h"
25 #include "libavutil/crc.h"
26 #include "libavutil/dict.h"
27 #include "libavutil/mathematics.h"
28 #include "avformat.h"
29 #include "internal.h"
30 #include "avio_internal.h"
31 #include "id3v2.h"
32 #include "id3v1.h"
33 #include "replaygain.h"
34 
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 {
45  AVClass *class;
46  int64_t filesize;
47  int xing_toc;
48  int start_pad;
49  int end_pad;
50  int usetoc;
51  unsigned frames; /* Total number of frames in file */
52  unsigned header_filesize; /* Total number of bytes in the stream */
53  int is_cbr;
55 
56 /* mp3 read */
57 
59 {
60  int max_frames, first_frames = 0;
61  int fsize, frames, sample_rate;
62  uint32_t header;
63  const uint8_t *buf, *buf0, *buf2, *end;
64  AVCodecContext avctx;
65 
66  buf0 = p->buf;
67  end = p->buf + p->buf_size - sizeof(uint32_t);
68  while(buf0 < end && !*buf0)
69  buf0++;
70 
71  max_frames = 0;
72  buf = buf0;
73 
74  for(; buf < end; buf= buf2+1) {
75  buf2 = buf;
76  if(ff_mpa_check_header(AV_RB32(buf2)))
77  continue;
78 
79  for(frames = 0; buf2 < end; frames++) {
80  header = AV_RB32(buf2);
81  fsize = avpriv_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);
82  if(fsize < 0)
83  break;
84  buf2 += fsize;
85  }
86  max_frames = FFMAX(max_frames, frames);
87  if(buf == buf0)
88  first_frames= frames;
89  }
90  // keep this in sync with ac3 probe, both need to avoid
91  // issues with MPEG-files!
92  if (first_frames>=4) return AVPROBE_SCORE_EXTENSION + 1;
93  else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;
94  else if(max_frames>=4 && max_frames >= p->buf_size/10000) return AVPROBE_SCORE_EXTENSION / 2;
95  else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)
97  else if(max_frames>=1 && max_frames >= p->buf_size/10000) return 1;
98  else return 0;
99 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
100 }
101 
102 static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
103 {
104  int i;
105  MP3DecContext *mp3 = s->priv_data;
106  int fill_index = mp3->usetoc && duration > 0;
107 
108  if (!filesize &&
109  !(filesize = avio_size(s->pb))) {
110  av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
111  fill_index = 0;
112  }
113 
114  for (i = 0; i < XING_TOC_COUNT; i++) {
115  uint8_t b = avio_r8(s->pb);
116  if (fill_index)
118  av_rescale(b, filesize, 256),
119  av_rescale(i, duration, XING_TOC_COUNT),
120  0, 0, AVINDEX_KEYFRAME);
121  }
122  if (fill_index)
123  mp3->xing_toc = 1;
124 }
125 
127  MPADecodeHeader *c, uint32_t spf)
128 {
129 #define LAST_BITS(k, n) ((k) & ((1 << (n)) - 1))
130 #define MIDDLE_BITS(k, m, n) LAST_BITS((k) >> (m), ((n) - (m)))
131 
132  uint16_t crc;
133  uint32_t v;
134 
135  char version[10];
136 
137  uint32_t peak = 0;
138  int32_t r_gain = INT32_MIN, a_gain = INT32_MIN;
139 
140  MP3DecContext *mp3 = s->priv_data;
141  static const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
142  uint64_t fsize = avio_size(s->pb);
143 
144  /* Check for Xing / Info tag */
145  avio_skip(s->pb, xing_offtbl[c->lsf == 1][c->nb_channels == 1]);
146  v = avio_rb32(s->pb);
147  mp3->is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
148  if (v != MKBETAG('X', 'i', 'n', 'g') && !mp3->is_cbr)
149  return;
150 
151  v = avio_rb32(s->pb);
152  if (v & XING_FLAG_FRAMES)
153  mp3->frames = avio_rb32(s->pb);
154  if (v & XING_FLAG_SIZE)
155  mp3->header_filesize = avio_rb32(s->pb);
156  if (fsize && mp3->header_filesize) {
157  uint64_t min, delta;
158  min = FFMIN(fsize, mp3->header_filesize);
159  delta = FFMAX(fsize, mp3->header_filesize) - min;
160  if (fsize > mp3->header_filesize && delta > min >> 4) {
161  mp3->frames = 0;
162  } else if (delta > min >> 4) {
164  "filesize and duration do not match (growing file?)\n");
165  }
166  }
167  if (v & XING_FLAG_TOC)
169  (AVRational){spf, c->sample_rate},
170  st->time_base));
171  /* VBR quality */
172  if (v & XING_FLAC_QSCALE)
173  avio_rb32(s->pb);
174 
175  /* Encoder short version string */
176  memset(version, 0, sizeof(version));
177  avio_read(s->pb, version, 9);
178 
179  /* Info Tag revision + VBR method */
180  avio_r8(s->pb);
181 
182  /* Lowpass filter value */
183  avio_r8(s->pb);
184 
185  /* ReplayGain peak */
186  v = avio_rb32(s->pb);
187  peak = av_rescale(v, 100000, 1 << 23);
188 
189  /* Radio ReplayGain */
190  v = avio_rb16(s->pb);
191 
192  if (MIDDLE_BITS(v, 13, 15) == 1) {
193  r_gain = MIDDLE_BITS(v, 0, 8) * 10000;
194 
195  if (v & (1 << 9))
196  r_gain *= -1;
197  }
198 
199  /* Audiophile ReplayGain */
200  v = avio_rb16(s->pb);
201 
202  if (MIDDLE_BITS(v, 13, 15) == 2) {
203  a_gain = MIDDLE_BITS(v, 0, 8) * 10000;
204 
205  if (v & (1 << 9))
206  a_gain *= -1;
207  }
208 
209  /* Encoding flags + ATH Type */
210  avio_r8(s->pb);
211 
212  /* if ABR {specified bitrate} else {minimal bitrate} */
213  avio_r8(s->pb);
214 
215  /* Encoder delays */
216  v= avio_rb24(s->pb);
217  if(AV_RB32(version) == MKBETAG('L', 'A', 'M', 'E')
218  || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'f')
219  || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'c')
220  ) {
221 
222  mp3->start_pad = v>>12;
223  mp3-> end_pad = v&4095;
224  st->skip_samples = mp3->start_pad + 528 + 1;
225  if (mp3->frames) {
226  st->first_discard_sample = -mp3->end_pad + 528 + 1 + mp3->frames * (int64_t)spf;
227  st->last_discard_sample = mp3->frames * (int64_t)spf;
228  }
229  if (!st->start_time)
230  st->start_time = av_rescale_q(st->skip_samples,
231  (AVRational){1, c->sample_rate},
232  st->time_base);
233  av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3-> end_pad);
234  }
235 
236  /* Misc */
237  avio_r8(s->pb);
238 
239  /* MP3 gain */
240  avio_r8(s->pb);
241 
242  /* Preset and surround info */
243  avio_rb16(s->pb);
244 
245  /* Music length */
246  avio_rb32(s->pb);
247 
248  /* Music CRC */
249  avio_rb16(s->pb);
250 
251  /* Info Tag CRC */
252  crc = ffio_get_checksum(s->pb);
253  v = avio_rb16(s->pb);
254 
255  if (v == crc) {
256  ff_replaygain_export_raw(st, r_gain, peak, a_gain, 0);
257  av_dict_set(&st->metadata, "encoder", version, 0);
258  }
259 }
260 
261 static void mp3_parse_vbri_tag(AVFormatContext *s, AVStream *st, int64_t base)
262 {
263  uint32_t v;
264  MP3DecContext *mp3 = s->priv_data;
265 
266  /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
267  avio_seek(s->pb, base + 4 + 32, SEEK_SET);
268  v = avio_rb32(s->pb);
269  if (v == MKBETAG('V', 'B', 'R', 'I')) {
270  /* Check tag version */
271  if (avio_rb16(s->pb) == 1) {
272  /* skip delay and quality */
273  avio_skip(s->pb, 4);
274  mp3->header_filesize = avio_rb32(s->pb);
275  mp3->frames = avio_rb32(s->pb);
276  }
277  }
278 }
279 
280 /**
281  * Try to find Xing/Info/VBRI tags and compute duration from info therein
282  */
283 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
284 {
285  uint32_t v, spf;
287  int vbrtag_size = 0;
288  MP3DecContext *mp3 = s->priv_data;
289 
291 
292  v = avio_rb32(s->pb);
293  if(ff_mpa_check_header(v) < 0)
294  return -1;
295 
296  if (avpriv_mpegaudio_decode_header(&c, v) == 0)
297  vbrtag_size = c.frame_size;
298  if(c.layer != 3)
299  return -1;
300 
301  spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
302 
303  mp3->frames = 0;
304  mp3->header_filesize = 0;
305 
306  mp3_parse_info_tag(s, st, &c, spf);
307  mp3_parse_vbri_tag(s, st, base);
308 
309  if (!mp3->frames && !mp3->header_filesize)
310  return -1;
311 
312  /* Skip the vbr tag frame */
313  avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
314 
315  if (mp3->frames)
316  st->duration = av_rescale_q(mp3->frames, (AVRational){spf, c.sample_rate},
317  st->time_base);
318  if (mp3->header_filesize && mp3->frames && !mp3->is_cbr)
319  st->codec->bit_rate = av_rescale(mp3->header_filesize, 8 * c.sample_rate, mp3->frames * (int64_t)spf);
320 
321  return 0;
322 }
323 
325 {
326  MP3DecContext *mp3 = s->priv_data;
327  AVStream *st;
328  int64_t off;
329  int ret;
330 
331  st = avformat_new_stream(s, NULL);
332  if (!st)
333  return AVERROR(ENOMEM);
334 
338  st->start_time = 0;
339 
340  // lcm of all mp3 sample rates
341  avpriv_set_pts_info(st, 64, 1, 14112000);
342 
343  s->pb->maxsize = -1;
344  off = avio_tell(s->pb);
345 
346  if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
347  ff_id3v1_read(s);
348 
349  if(s->pb->seekable)
350  mp3->filesize = avio_size(s->pb);
351 
352  if (mp3_parse_vbr_tags(s, st, off) < 0)
353  avio_seek(s->pb, off, SEEK_SET);
354 
355  ret = ff_replaygain_export(st, s->metadata);
356  if (ret < 0)
357  return ret;
358 
359  /* the parameters will be extracted from the compressed bitstream */
360  return 0;
361 }
362 
363 #define MP3_PACKET_SIZE 1024
364 
366 {
367  MP3DecContext *mp3 = s->priv_data;
368  int ret, size;
369  int64_t pos;
370 
371  size= MP3_PACKET_SIZE;
372  pos = avio_tell(s->pb);
373  if(mp3->filesize > ID3v1_TAG_SIZE && pos < mp3->filesize)
374  size= FFMIN(size, mp3->filesize - pos);
375 
376  ret= av_get_packet(s->pb, pkt, size);
377  if (ret <= 0) {
378  if(ret<0)
379  return ret;
380  return AVERROR_EOF;
381  }
382 
383  pkt->flags &= ~AV_PKT_FLAG_CORRUPT;
384  pkt->stream_index = 0;
385 
386  if (ret >= ID3v1_TAG_SIZE &&
387  memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
388  ret -= ID3v1_TAG_SIZE;
389 
390  /* note: we need to modify the packet size here to handle the last
391  packet */
392  pkt->size = ret;
393  return ret;
394 }
395 
396 static int check(AVFormatContext *s, int64_t pos)
397 {
398  int64_t ret = avio_seek(s->pb, pos, SEEK_SET);
399  unsigned header;
400  MPADecodeHeader sd;
401  if (ret < 0)
402  return ret;
403  header = avio_rb32(s->pb);
404  if (ff_mpa_check_header(header) < 0)
405  return -1;
406  if (avpriv_mpegaudio_decode_header(&sd, header) == 1)
407  return -1;
408  return sd.frame_size;
409 }
410 
411 static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
412  int flags)
413 {
414  MP3DecContext *mp3 = s->priv_data;
415  AVIndexEntry *ie, ie1;
416  AVStream *st = s->streams[0];
417  int64_t ret = av_index_search_timestamp(st, timestamp, flags);
418  int i, j;
419  int dir = (flags&AVSEEK_FLAG_BACKWARD) ? -1 : 1;
420  int64_t best_pos;
421  int best_score;
422 
423  if ( mp3->is_cbr
424  && st->duration > 0
425  && mp3->header_filesize > s->data_offset
426  && mp3->frames) {
427  int64_t filesize = avio_size(s->pb);
428  int64_t duration;
429  if (filesize <= s->data_offset)
430  filesize = mp3->header_filesize;
431  filesize -= s->data_offset;
432  duration = av_rescale(st->duration, filesize, mp3->header_filesize - s->data_offset);
433  ie = &ie1;
434  timestamp = av_clip64(timestamp, 0, duration);
435  ie->timestamp = timestamp;
436  ie->pos = av_rescale(timestamp, filesize, duration) + s->data_offset;
437  } else if (mp3->xing_toc) {
438  if (ret < 0)
439  return ret;
440 
441  ie = &st->index_entries[ret];
442  } else {
443  st->skip_samples = timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;
444 
445  return -1;
446  }
447 
448  avio_seek(s->pb, FFMAX(ie->pos - 4096, 0), SEEK_SET);
449  ret = avio_seek(s->pb, ie->pos, SEEK_SET);
450  if (ret < 0)
451  return ret;
452 
453 #define MIN_VALID 3
454  best_pos = ie->pos;
455  best_score = 999;
456  for(i=0; i<4096; i++) {
457  int64_t pos = ie->pos + (dir > 0 ? i - 1024 : -i);
458  int64_t candidate = -1;
459  int score = 999;
460  for(j=0; j<MIN_VALID; j++) {
461  ret = check(s, pos);
462  if(ret < 0)
463  break;
464  if ((ie->pos - pos)*dir <= 0 && abs(MIN_VALID/2-j) < score) {
465  candidate = pos;
466  score = abs(MIN_VALID/2-j);
467  }
468  pos += ret;
469  }
470  if (best_score > score && j == MIN_VALID) {
471  best_pos = candidate;
472  best_score = score;
473  if(score == 0)
474  break;
475  }
476  }
477 
478  ret = avio_seek(s->pb, best_pos, SEEK_SET);
479  if (ret < 0)
480  return ret;
481  ff_update_cur_dts(s, st, ie->timestamp);
482  st->skip_samples = ie->timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;
483  return 0;
484 }
485 
486 static const AVOption options[] = {
487  { "usetoc", "use table of contents", offsetof(MP3DecContext, usetoc), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 1, AV_OPT_FLAG_DECODING_PARAM},
488  { NULL },
489 };
490 
491 static const AVClass demuxer_class = {
492  .class_name = "mp3",
493  .item_name = av_default_item_name,
494  .option = options,
495  .version = LIBAVUTIL_VERSION_INT,
496  .category = AV_CLASS_CATEGORY_DEMUXER,
497 };
498 
500  .name = "mp3",
501  .long_name = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
502  .read_probe = mp3_read_probe,
503  .read_header = mp3_read_header,
504  .read_packet = mp3_read_packet,
505  .read_seek = mp3_seek,
506  .priv_data_size = sizeof(MP3DecContext),
508  .extensions = "mp2,mp3,m2a,mpa", /* XXX: use probe */
509  .priv_class = &demuxer_class,
510 };