aboutsummaryrefslogtreecommitdiffstats
path: root/libavformat/mp3dec.c
blob: 519d046211941f31892d5c26b1c8e6d40e390820 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
/*
 * MP3 demuxer
 * Copyright (c) 2003 Fabrice Bellard
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/opt.h"
#include "libavutil/avstring.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/crc.h"
#include "libavutil/dict.h"
#include "libavutil/mathematics.h"
#include "avformat.h"
#include "internal.h"
#include "avio_internal.h"
#include "id3v2.h"
#include "id3v1.h"
#include "replaygain.h"

#include "libavcodec/mpegaudiodecheader.h"

#define XING_FLAG_FRAMES 0x01
#define XING_FLAG_SIZE   0x02
#define XING_FLAG_TOC    0x04
#define XING_FLAC_QSCALE 0x08

#define XING_TOC_COUNT 100

typedef struct {
    AVClass *class;
    int64_t filesize;
    int xing_toc;
    int start_pad;
    int end_pad;
    int usetoc;
    unsigned frames; /* Total number of frames in file */
    unsigned header_filesize;   /* Total number of bytes in the stream */
    int is_cbr;
} MP3DecContext;

/* mp3 read */

static int mp3_read_probe(AVProbeData *p)
{
    int max_frames, first_frames = 0;
    int fsize, frames;
    uint32_t header;
    const uint8_t *buf, *buf0, *buf2, *end;
    AVCodecContext avctx;

    buf0 = p->buf;
    end = p->buf + p->buf_size - sizeof(uint32_t);
    while(buf0 < end && !*buf0)
        buf0++;

    max_frames = 0;
    buf = buf0;

    for(; buf < end; buf= buf2+1) {
        buf2 = buf;
        if(ff_mpa_check_header(AV_RB32(buf2)))
            continue;

        for(frames = 0; buf2 < end; frames++) {
            int dummy;
            header = AV_RB32(buf2);
            fsize = avpriv_mpa_decode_header(&avctx, header, &dummy, &dummy, &dummy, &dummy);
            if(fsize < 0)
                break;
            buf2 += fsize;
        }
        max_frames = FFMAX(max_frames, frames);
        if(buf == buf0)
            first_frames= frames;
    }
    // keep this in sync with ac3 probe, both need to avoid
    // issues with MPEG-files!
    if   (first_frames>=4) return AVPROBE_SCORE_EXTENSION + 1;
    else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;
    else if(max_frames>=4 && max_frames >= p->buf_size/10000) return AVPROBE_SCORE_EXTENSION / 2;
    else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)
                           return p->buf_size < PROBE_BUF_MAX ? AVPROBE_SCORE_EXTENSION / 4 : AVPROBE_SCORE_EXTENSION - 2;
    else if(max_frames>=1 && max_frames >= p->buf_size/10000) return 1;
    else                   return 0;
//mpegps_mp3_unrecognized_format.mpg has max_frames=3
}

static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
{
    int i;
    MP3DecContext *mp3 = s->priv_data;
    int fill_index = mp3->usetoc && duration > 0;

    if (!filesize &&
        !(filesize = avio_size(s->pb))) {
        av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
        fill_index = 0;
    }

    for (i = 0; i < XING_TOC_COUNT; i++) {
        uint8_t b = avio_r8(s->pb);
        if (fill_index)
            av_add_index_entry(s->streams[0],
                           av_rescale(b, filesize, 256),
                           av_rescale(i, duration, XING_TOC_COUNT),
                           0, 0, AVINDEX_KEYFRAME);
    }
    if (fill_index)
        mp3->xing_toc = 1;
}

static void mp3_parse_info_tag(AVFormatContext *s, AVStream *st,
                               MPADecodeHeader *c, uint32_t spf)
{
#define LAST_BITS(k, n) ((k) & ((1 << (n)) - 1))
#define MIDDLE_BITS(k, m, n) LAST_BITS((k) >> (m), ((n) - (m)))

    uint16_t crc;
    uint32_t v;

    char version[10];

    uint32_t peak   = 0;
    int32_t  r_gain = INT32_MIN, a_gain = INT32_MIN;

    MP3DecContext *mp3 = s->priv_data;
    static const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
    uint64_t fsize = avio_size(s->pb);

    /* Check for Xing / Info tag */
    avio_skip(s->pb, xing_offtbl[c->lsf == 1][c->nb_channels == 1]);
    v = avio_rb32(s->pb);
    mp3->is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
    if (v != MKBETAG('X', 'i', 'n', 'g') && !mp3->is_cbr)
        return;

    v = avio_rb32(s->pb);
    if (v & XING_FLAG_FRAMES)
        mp3->frames = avio_rb32(s->pb);
    if (v & XING_FLAG_SIZE)
        mp3->header_filesize = avio_rb32(s->pb);
    if (fsize && mp3->header_filesize) {
        uint64_t min, delta;
        min = FFMIN(fsize, mp3->header_filesize);
        delta = FFMAX(fsize, mp3->header_filesize) - min;
        if (fsize > mp3->header_filesize && delta > min >> 4) {
            mp3->frames = 0;
        } else if (delta > min >> 4) {
            av_log(s, AV_LOG_WARNING,
                   "filesize and duration do not match (growing file?)\n");
        }
    }
    if (v & XING_FLAG_TOC)
        read_xing_toc(s, mp3->header_filesize, av_rescale_q(mp3->frames,
                                       (AVRational){spf, c->sample_rate},
                                       st->time_base));
    /* VBR quality */
    if (v & XING_FLAC_QSCALE)
        avio_rb32(s->pb);

    /* Encoder short version string */
    memset(version, 0, sizeof(version));
    avio_read(s->pb, version, 9);

    /* Info Tag revision + VBR method */
    avio_r8(s->pb);

    /* Lowpass filter value */
    avio_r8(s->pb);

    /* ReplayGain peak */
    v    = avio_rb32(s->pb);
    peak = av_rescale(v, 100000, 1 << 23);

    /* Radio ReplayGain */
    v = avio_rb16(s->pb);

    if (MIDDLE_BITS(v, 13, 15) == 1) {
        r_gain = MIDDLE_BITS(v, 0, 8) * 10000;

        if (v & (1 << 9))
            r_gain *= -1;
    }

    /* Audiophile ReplayGain */
    v = avio_rb16(s->pb);

    if (MIDDLE_BITS(v, 13, 15) == 2) {
        a_gain = MIDDLE_BITS(v, 0, 8) * 10000;

        if (v & (1 << 9))
            a_gain *= -1;
    }

    /* Encoding flags + ATH Type */
    avio_r8(s->pb);

    /* if ABR {specified bitrate} else {minimal bitrate} */
    avio_r8(s->pb);

    /* Encoder delays */
    v= avio_rb24(s->pb);
    if(AV_RB32(version) == MKBETAG('L', 'A', 'M', 'E')
        || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'f')
        || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'c')
    ) {

        mp3->start_pad = v>>12;
        mp3->  end_pad = v&4095;
        st->skip_samples = mp3->start_pad + 528 + 1;
        if (mp3->frames) {
            st->first_discard_sample = -mp3->end_pad + 528 + 1 + mp3->frames * (int64_t)spf;
            st->last_discard_sample = mp3->frames * (int64_t)spf;
        }
        if (!st->start_time)
            st->start_time = av_rescale_q(st->skip_samples,
                                            (AVRational){1, c->sample_rate},
                                            st->time_base);
        av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3->  end_pad);
    }

    /* Misc */
    avio_r8(s->pb);

    /* MP3 gain */
    avio_r8(s->pb);

    /* Preset and surround info */
    avio_rb16(s->pb);

    /* Music length */
    avio_rb32(s->pb);

    /* Music CRC */
    avio_rb16(s->pb);

    /* Info Tag CRC */
    crc = ffio_get_checksum(s->pb);
    v   = avio_rb16(s->pb);

    if (v == crc) {
        ff_replaygain_export_raw(st, r_gain, peak, a_gain, 0);
        av_dict_set(&st->metadata, "encoder", version, 0);
    }
}

static void mp3_parse_vbri_tag(AVFormatContext *s, AVStream *st, int64_t base)
{
    uint32_t v;
    MP3DecContext *mp3 = s->priv_data;

    /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
    avio_seek(s->pb, base + 4 + 32, SEEK_SET);
    v = avio_rb32(s->pb);
    if (v == MKBETAG('V', 'B', 'R', 'I')) {
        /* Check tag version */
        if (avio_rb16(s->pb) == 1) {
            /* skip delay and quality */
            avio_skip(s->pb, 4);
            mp3->header_filesize = avio_rb32(s->pb);
            mp3->frames = avio_rb32(s->pb);
        }
    }
}

/**
 * Try to find Xing/Info/VBRI tags and compute duration from info therein
 */
static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
{
    uint32_t v, spf;
    MPADecodeHeader c;
    int vbrtag_size = 0;
    MP3DecContext *mp3 = s->priv_data;

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

    v = avio_rb32(s->pb);
    if(ff_mpa_check_header(v) < 0)
      return -1;

    if (avpriv_mpegaudio_decode_header(&c, v) == 0)
        vbrtag_size = c.frame_size;
    if(c.layer != 3)
        return -1;

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

    mp3->frames = 0;
    mp3->header_filesize   = 0;

    mp3_parse_info_tag(s, st, &c, spf);
    mp3_parse_vbri_tag(s, st, base);

    if (!mp3->frames && !mp3->header_filesize)
        return -1;

    /* Skip the vbr tag frame */
    avio_seek(s->pb, base + vbrtag_size, SEEK_SET);

    if (mp3->frames)
        st->duration = av_rescale_q(mp3->frames, (AVRational){spf, c.sample_rate},
                                    st->time_base);
    if (mp3->header_filesize && mp3->frames && !mp3->is_cbr)
        st->codec->bit_rate = av_rescale(mp3->header_filesize, 8 * c.sample_rate, mp3->frames * (int64_t)spf);

    return 0;
}

static int mp3_read_header(AVFormatContext *s)
{
    MP3DecContext *mp3 = s->priv_data;
    AVStream *st;
    int64_t off;
    int ret;

    st = avformat_new_stream(s, NULL);
    if (!st)
        return AVERROR(ENOMEM);

    st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
    st->codec->codec_id = AV_CODEC_ID_MP3;
    st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
    st->start_time = 0;

    // lcm of all mp3 sample rates
    avpriv_set_pts_info(st, 64, 1, 14112000);

    s->pb->maxsize = -1;
    off = avio_tell(s->pb);

    if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
        ff_id3v1_read(s);

    if(s->pb->seekable)
        mp3->filesize = avio_size(s->pb);

    if (mp3_parse_vbr_tags(s, st, off) < 0)
        avio_seek(s->pb, off, SEEK_SET);

    ret = ff_replaygain_export(st, s->metadata);
    if (ret < 0)
        return ret;

    /* the parameters will be extracted from the compressed bitstream */
    return 0;
}

#define MP3_PACKET_SIZE 1024

static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    MP3DecContext *mp3 = s->priv_data;
    int ret, size;
    int64_t pos;

    size= MP3_PACKET_SIZE;
    pos = avio_tell(s->pb);
    if(mp3->filesize > ID3v1_TAG_SIZE && pos < mp3->filesize)
        size= FFMIN(size, mp3->filesize - pos);

    ret= av_get_packet(s->pb, pkt, size);
    if (ret <= 0) {
        if(ret<0)
            return ret;
        return AVERROR_EOF;
    }

    pkt->flags &= ~AV_PKT_FLAG_CORRUPT;
    pkt->stream_index = 0;

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

    /* note: we need to modify the packet size here to handle the last
       packet */
    pkt->size = ret;
    return ret;
}

static int check(AVFormatContext *s, int64_t pos)
{
    int64_t ret = avio_seek(s->pb, pos, SEEK_SET);
    unsigned header;
    MPADecodeHeader sd;
    if (ret < 0)
        return ret;
    header = avio_rb32(s->pb);
    if (ff_mpa_check_header(header) < 0)
        return -1;
    if (avpriv_mpegaudio_decode_header(&sd, header) == 1)
        return -1;
    return sd.frame_size;
}

static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
                    int flags)
{
    MP3DecContext *mp3 = s->priv_data;
    AVIndexEntry *ie, ie1;
    AVStream *st = s->streams[0];
    int64_t ret  = av_index_search_timestamp(st, timestamp, flags);
    int i, j;
    int dir = (flags&AVSEEK_FLAG_BACKWARD) ? -1 : 1;
    int64_t best_pos;
    int best_score;

    if (   mp3->is_cbr
        && st->duration > 0
        && mp3->header_filesize > s->data_offset
        && mp3->frames) {
        int64_t filesize = avio_size(s->pb);
        int64_t duration;
        if (filesize <= s->data_offset)
            filesize = mp3->header_filesize;
        filesize -= s->data_offset;
        duration = av_rescale(st->duration, filesize, mp3->header_filesize - s->data_offset);
        ie = &ie1;
        timestamp = av_clip64(timestamp, 0, duration);
        ie->timestamp = timestamp;
        ie->pos       = av_rescale(timestamp, filesize, duration) + s->data_offset;
    } else if (mp3->xing_toc) {
        if (ret < 0)
            return ret;

        ie = &st->index_entries[ret];
    } else {
        st->skip_samples = timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;

        return -1;
    }

    avio_seek(s->pb, FFMAX(ie->pos - 4096, 0), SEEK_SET);
    ret = avio_seek(s->pb, ie->pos, SEEK_SET);
    if (ret < 0)
        return ret;

#define MIN_VALID 3
    best_pos = ie->pos;
    best_score = 999;
    for(i=0; i<4096; i++) {
        int64_t pos = ie->pos + (dir > 0 ? i - 1024 : -i);
        int64_t candidate = -1;
        int score = 999;

        if (pos < 0)
            continue;

        for(j=0; j<MIN_VALID; j++) {
            ret = check(s, pos);
            if(ret < 0)
                break;
            if ((ie->pos - pos)*dir <= 0 && abs(MIN_VALID/2-j) < score) {
                candidate = pos;
                score = abs(MIN_VALID/2-j);
            }
            pos += ret;
        }
        if (best_score > score && j == MIN_VALID) {
            best_pos = candidate;
            best_score = score;
            if(score == 0)
                break;
        }
    }

    ret = avio_seek(s->pb, best_pos, SEEK_SET);
    if (ret < 0)
        return ret;
    ff_update_cur_dts(s, st, ie->timestamp);
    st->skip_samples = ie->timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;
    return 0;
}

static const AVOption options[] = {
    { "usetoc", "use table of contents", offsetof(MP3DecContext, usetoc), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 1, AV_OPT_FLAG_DECODING_PARAM},
    { NULL },
};

static const AVClass demuxer_class = {
    .class_name = "mp3",
    .item_name  = av_default_item_name,
    .option     = options,
    .version    = LIBAVUTIL_VERSION_INT,
    .category   = AV_CLASS_CATEGORY_DEMUXER,
};

AVInputFormat ff_mp3_demuxer = {
    .name           = "mp3",
    .long_name      = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
    .read_probe     = mp3_read_probe,
    .read_header    = mp3_read_header,
    .read_packet    = mp3_read_packet,
    .read_seek      = mp3_seek,
    .priv_data_size = sizeof(MP3DecContext),
    .flags          = AVFMT_GENERIC_INDEX,
    .extensions     = "mp2,mp3,m2a,mpa", /* XXX: use probe */
    .priv_class     = &demuxer_class,
};