FFmpeg: libavformat/mp3dec.c Source File

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libavformat

mp3dec.c

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1 /*

2 * MP3 demuxer

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 */

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"

35 #include "libavcodec/mpegaudiodecheader.h"

37 #define XING_FLAG_FRAMES 0x01

38 #define XING_FLAG_SIZE 0x02

39 #define XING_FLAG_TOC 0x04

40 #define XING_FLAC_QSCALE 0x08

42 #define XING_TOC_COUNT 100

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;

54 } MP3DecContext;

56 /* mp3 read */

58 static int mp3_read_probe(AVProbeData *p)

59 {

60 int max_frames, first_frames = 0;

61 int fsize, frames;

62 uint32_t header;

63 const uint8_t *buf, *buf0, *buf2, *end;

64 AVCodecContext *avctx = avcodec_alloc_context3(NULL);

66 if (!avctx)

67 return 0;

69 buf0 = p->buf;

70 end = p->buf + p->buf_size - sizeof(uint32_t);

71 while(buf0 < end && !*buf0)

72 buf0++;

74 max_frames = 0;

75 buf = buf0;

77 for(; buf < end; buf= buf2+1) {

78 buf2 = buf;

79 if(ff_mpa_check_header(AV_RB32(buf2)))

80 continue;

82 for(frames = 0; buf2 < end; frames++) {

83 int dummy;

84 header = AV_RB32(buf2);

85 fsize = avpriv_mpa_decode_header(avctx, header, &dummy, &dummy, &dummy, &dummy);

86 if(fsize < 0)

87 break;

88 buf2 += fsize;

89 }

90 max_frames = FFMAX(max_frames, frames);

91 if(buf == buf0)

92 first_frames= frames;

93 }

94 avcodec_free_context(&avctx);

95 // keep this in sync with ac3 probe, both need to avoid

96 // issues with MPEG-files!

97 if (first_frames>=4) return AVPROBE_SCORE_EXTENSION + 1;

98 else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;

99 else if(max_frames>=4 && max_frames >= p->buf_size/10000) return AVPROBE_SCORE_EXTENSION / 2;

100 else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)

101 return p->buf_size < PROBE_BUF_MAX ? AVPROBE_SCORE_EXTENSION / 4 : AVPROBE_SCORE_EXTENSION - 2;

102 else if(max_frames>=1 && max_frames >= p->buf_size/10000) return 1;

103 else return 0;

104 //mpegps_mp3_unrecognized_format.mpg has max_frames=3

105 }

106

107 static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)

108 {

109 int i;

110 MP3DecContext *mp3 = s->priv_data;

111 int fill_index = mp3->usetoc && duration > 0;

112

113 if (!filesize &&

114 !(filesize = avio_size(s->pb))) {

115 av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");

116 fill_index = 0;

117 }

118

119 for (i = 0; i < XING_TOC_COUNT; i++) {

120 uint8_t b = avio_r8(s->pb);

121 if (fill_index)

122 av_add_index_entry(s->streams[0],

123 av_rescale(b, filesize, 256),

124 av_rescale(i, duration, XING_TOC_COUNT),

125 0, 0, AVINDEX_KEYFRAME);

126 }

127 if (fill_index)

128 mp3->xing_toc = 1;

129 }

130

131 static void mp3_parse_info_tag(AVFormatContext *s, AVStream *st,

132 MPADecodeHeader *c, uint32_t spf)

133 {

134 #define LAST_BITS(k, n) ((k) & ((1 << (n)) - 1))

135 #define MIDDLE_BITS(k, m, n) LAST_BITS((k) >> (m), ((n) - (m)))

136

137 uint16_t crc;

138 uint32_t v;

139

140 char version[10];

141

142 uint32_t peak = 0;

143 int32_t r_gain = INT32_MIN, a_gain = INT32_MIN;

144

145 MP3DecContext *mp3 = s->priv_data;

146 static const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};

147 uint64_t fsize = avio_size(s->pb);

148

149 /* Check for Xing / Info tag */

150 avio_skip(s->pb, xing_offtbl[c->lsf == 1][c->nb_channels == 1]);

151 v = avio_rb32(s->pb);

152 mp3->is_cbr = v == MKBETAG('I', 'n', 'f', 'o');

153 if (v != MKBETAG('X', 'i', 'n', 'g') && !mp3->is_cbr)

154 return;

155

156 v = avio_rb32(s->pb);

157 if (v & XING_FLAG_FRAMES)

158 mp3->frames = avio_rb32(s->pb);

159 if (v & XING_FLAG_SIZE)

160 mp3->header_filesize = avio_rb32(s->pb);

161 if (fsize && mp3->header_filesize) {

162 uint64_t min, delta;

163 min = FFMIN(fsize, mp3->header_filesize);

164 delta = FFMAX(fsize, mp3->header_filesize) - min;

165 if (fsize > mp3->header_filesize && delta > min >> 4) {

166 mp3->frames = 0;

167 } else if (delta > min >> 4) {

168 av_log(s, AV_LOG_WARNING,

169 "filesize and duration do not match (growing file?)\n");

170 }

171 }

172 if (v & XING_FLAG_TOC)

173 read_xing_toc(s, mp3->header_filesize, av_rescale_q(mp3->frames,

174 (AVRational){spf, c->sample_rate},

175 st->time_base));

176 /* VBR quality */

177 if (v & XING_FLAC_QSCALE)

178 avio_rb32(s->pb);

179

180 /* Encoder short version string */

181 memset(version, 0, sizeof(version));

182 avio_read(s->pb, version, 9);

183

184 /* Info Tag revision + VBR method */

185 avio_r8(s->pb);

186

187 /* Lowpass filter value */

188 avio_r8(s->pb);

189

190 /* ReplayGain peak */

191 v = avio_rb32(s->pb);

192 peak = av_rescale(v, 100000, 1 << 23);

193

194 /* Radio ReplayGain */

195 v = avio_rb16(s->pb);

196

197 if (MIDDLE_BITS(v, 13, 15) == 1) {

198 r_gain = MIDDLE_BITS(v, 0, 8) * 10000;

199

200 if (v & (1 << 9))

201 r_gain *= -1;

202 }

203

204 /* Audiophile ReplayGain */

205 v = avio_rb16(s->pb);

206

207 if (MIDDLE_BITS(v, 13, 15) == 2) {

208 a_gain = MIDDLE_BITS(v, 0, 8) * 10000;

209

210 if (v & (1 << 9))

211 a_gain *= -1;

212 }

213

214 /* Encoding flags + ATH Type */

215 avio_r8(s->pb);

216

217 /* if ABR {specified bitrate} else {minimal bitrate} */

218 avio_r8(s->pb);

219

220 /* Encoder delays */

221 v= avio_rb24(s->pb);

222 if(AV_RB32(version) == MKBETAG('L', 'A', 'M', 'E')

223 || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'f')

224 || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'c')

225 ) {

226

227 mp3->start_pad = v>>12;

228 mp3-> end_pad = v&4095;

229 st->skip_samples = mp3->start_pad + 528 + 1;

230 if (mp3->frames) {

231 st->first_discard_sample = -mp3->end_pad + 528 + 1 + mp3->frames * (int64_t)spf;

232 st->last_discard_sample = mp3->frames * (int64_t)spf;

233 }

234 if (!st->start_time)

235 st->start_time = av_rescale_q(st->skip_samples,

236 (AVRational){1, c->sample_rate},

237 st->time_base);

238 av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3-> end_pad);

239 }

240

241 /* Misc */

242 avio_r8(s->pb);

243

244 /* MP3 gain */

245 avio_r8(s->pb);

246

247 /* Preset and surround info */

248 avio_rb16(s->pb);

249

250 /* Music length */

251 avio_rb32(s->pb);

252

253 /* Music CRC */

254 avio_rb16(s->pb);

255

256 /* Info Tag CRC */

257 crc = ffio_get_checksum(s->pb);

258 v = avio_rb16(s->pb);

259

260 if (v == crc) {

261 ff_replaygain_export_raw(st, r_gain, peak, a_gain, 0);

262 av_dict_set(&st->metadata, "encoder", version, 0);

263 }

264 }

265

266 static void mp3_parse_vbri_tag(AVFormatContext *s, AVStream *st, int64_t base)

267 {

268 uint32_t v;

269 MP3DecContext *mp3 = s->priv_data;

270

271 /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */

272 avio_seek(s->pb, base + 4 + 32, SEEK_SET);

273 v = avio_rb32(s->pb);

274 if (v == MKBETAG('V', 'B', 'R', 'I')) {

275 /* Check tag version */

276 if (avio_rb16(s->pb) == 1) {

277 /* skip delay and quality */

278 avio_skip(s->pb, 4);

279 mp3->header_filesize = avio_rb32(s->pb);

280 mp3->frames = avio_rb32(s->pb);

281 }

282 }

283 }

284

285 /**

286 * Try to find Xing/Info/VBRI tags and compute duration from info therein

287 */

288 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)

289 {

290 uint32_t v, spf;

291 MPADecodeHeader c;

292 int vbrtag_size = 0;

293 MP3DecContext *mp3 = s->priv_data;

294

295 ffio_init_checksum(s->pb, ff_crcA001_update, 0);

296

297 v = avio_rb32(s->pb);

298 if(ff_mpa_check_header(v) < 0)

299 return -1;

300

301 if (avpriv_mpegaudio_decode_header(&c, v) == 0)

302 vbrtag_size = c.frame_size;

303 if(c.layer != 3)

304 return -1;

305

306 spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */

307

308 mp3->frames = 0;

309 mp3->header_filesize = 0;

310

311 mp3_parse_info_tag(s, st, &c, spf);

312 mp3_parse_vbri_tag(s, st, base);

313

314 if (!mp3->frames && !mp3->header_filesize)

315 return -1;

316

317 /* Skip the vbr tag frame */

318 avio_seek(s->pb, base + vbrtag_size, SEEK_SET);

319

320 if (mp3->frames)

321 st->duration = av_rescale_q(mp3->frames, (AVRational){spf, c.sample_rate},

322 st->time_base);

323 if (mp3->header_filesize && mp3->frames && !mp3->is_cbr)

324 st->codec->bit_rate = av_rescale(mp3->header_filesize, 8 * c.sample_rate, mp3->frames * (int64_t)spf);

325

326 return 0;

327 }

328

329 static int mp3_read_header(AVFormatContext *s)

330 {

331 MP3DecContext *mp3 = s->priv_data;

332 AVStream *st;

333 int64_t off;

334 int ret;

335

336 st = avformat_new_stream(s, NULL);

337 if (!st)

338 return AVERROR(ENOMEM);

339

340 st->codec->codec_type = AVMEDIA_TYPE_AUDIO;

341 st->codec->codec_id = AV_CODEC_ID_MP3;

342 st->need_parsing = AVSTREAM_PARSE_FULL_RAW;

343 st->start_time = 0;

344

345 // lcm of all mp3 sample rates

346 avpriv_set_pts_info(st, 64, 1, 14112000);

347

348 s->pb->maxsize = -1;

349 off = avio_tell(s->pb);

350

351 if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))

352 ff_id3v1_read(s);

353

354 if(s->pb->seekable)

355 mp3->filesize = avio_size(s->pb);

356

357 if (mp3_parse_vbr_tags(s, st, off) < 0)

358 avio_seek(s->pb, off, SEEK_SET);

359

360 ret = ff_replaygain_export(st, s->metadata);

361 if (ret < 0)

362 return ret;

363

364 /* the parameters will be extracted from the compressed bitstream */

365 return 0;

366 }

367

368 #define MP3_PACKET_SIZE 1024

369

370 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)

371 {

372 MP3DecContext *mp3 = s->priv_data;

373 int ret, size;

374 int64_t pos;

375

376 size= MP3_PACKET_SIZE;

377 pos = avio_tell(s->pb);

378 if(mp3->filesize > ID3v1_TAG_SIZE && pos < mp3->filesize)

379 size= FFMIN(size, mp3->filesize - pos);

380

381 ret= av_get_packet(s->pb, pkt, size);

382 if (ret <= 0) {

383 if(ret<0)

384 return ret;

385 return AVERROR_EOF;

386 }

387

388 pkt->flags &= ~AV_PKT_FLAG_CORRUPT;

389 pkt->stream_index = 0;

390

391 if (ret >= ID3v1_TAG_SIZE &&

392 memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)

393 ret -= ID3v1_TAG_SIZE;

394

395 /* note: we need to modify the packet size here to handle the last

396 packet */

397 pkt->size = ret;

398 return ret;

399 }

400

401 static int check(AVFormatContext *s, int64_t pos)

402 {

403 int64_t ret = avio_seek(s->pb, pos, SEEK_SET);

404 unsigned header;

405 MPADecodeHeader sd;

406 if (ret < 0)

407 return ret;

408 header = avio_rb32(s->pb);

409 if (ff_mpa_check_header(header) < 0)

410 return -1;

411 if (avpriv_mpegaudio_decode_header(&sd, header) == 1)

412 return -1;

413 return sd.frame_size;

414 }

415

416 static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,

417 int flags)

418 {

419 MP3DecContext *mp3 = s->priv_data;

420 AVIndexEntry *ie, ie1;

421 AVStream *st = s->streams[0];

422 int64_t ret = av_index_search_timestamp(st, timestamp, flags);

423 int i, j;

424 int dir = (flags&AVSEEK_FLAG_BACKWARD) ? -1 : 1;

425 int64_t best_pos;

426 int best_score;

427

428 if ( mp3->is_cbr

429 && st->duration > 0

430 && mp3->header_filesize > s->internal->data_offset

431 && mp3->frames) {

432 int64_t filesize = avio_size(s->pb);

433 int64_t duration;

434 if (filesize <= s->internal->data_offset)

435 filesize = mp3->header_filesize;

436 filesize -= s->internal->data_offset;

437 duration = av_rescale(st->duration, filesize, mp3->header_filesize - s->internal->data_offset);

438 ie = &ie1;

439 timestamp = av_clip64(timestamp, 0, duration);

440 ie->timestamp = timestamp;

441 ie->pos = av_rescale(timestamp, filesize, duration) + s->internal->data_offset;

442 } else if (mp3->xing_toc) {

443 if (ret < 0)

444 return ret;

445

446 ie = &st->index_entries[ret];

447 } else {

448 st->skip_samples = timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;

449

450 return -1;

451 }

452

453 avio_seek(s->pb, FFMAX(ie->pos - 4096, 0), SEEK_SET);

454 ret = avio_seek(s->pb, ie->pos, SEEK_SET);

455 if (ret < 0)

456 return ret;

457

458 #define MIN_VALID 3

459 best_pos = ie->pos;

460 best_score = 999;

461 for(i=0; i<4096; i++) {

462 int64_t pos = ie->pos + (dir > 0 ? i - 1024 : -i);

463 int64_t candidate = -1;

464 int score = 999;

465

466 if (pos < 0)

467 continue;

468

469 for(j=0; j<MIN_VALID; j++) {

470 ret = check(s, pos);

471 if(ret < 0)

472 break;

473 if ((ie->pos - pos)*dir <= 0 && abs(MIN_VALID/2-j) < score) {

474 candidate = pos;

475 score = abs(MIN_VALID/2-j);

476 }

477 pos += ret;

478 }

479 if (best_score > score && j == MIN_VALID) {

480 best_pos = candidate;

481 best_score = score;

482 if(score == 0)

483 break;

484 }

485 }

486

487 ret = avio_seek(s->pb, best_pos, SEEK_SET);

488 if (ret < 0)

489 return ret;

490 ff_update_cur_dts(s, st, ie->timestamp);

491 st->skip_samples = ie->timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;

492 return 0;

493 }

494

495 static const AVOption options[] = {

496 { "usetoc", "use table of contents", offsetof(MP3DecContext, usetoc), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 1, AV_OPT_FLAG_DECODING_PARAM},

497 { NULL },

498 };

499

500 static const AVClass demuxer_class = {

501 .class_name = "mp3",

502 .item_name = av_default_item_name,

503 .option = options,

504 .version = LIBAVUTIL_VERSION_INT,

505 .category = AV_CLASS_CATEGORY_DEMUXER,

506 };

507

508 AVInputFormat ff_mp3_demuxer = {

509 .name = "mp3",

510 .long_name = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),

511 .read_probe = mp3_read_probe,

512 .read_header = mp3_read_header,

513 .read_packet = mp3_read_packet,

514 .read_seek = mp3_seek,

515 .priv_data_size = sizeof(MP3DecContext),

516 .flags = AVFMT_GENERIC_INDEX,

517 .extensions = "mp2,mp3,m2a,mpa", /* XXX: use probe */

518 .priv_class = &demuxer_class,

519 };

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