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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/dict.h"
  26. #include "libavutil/mathematics.h"
  27. #include "avformat.h"
  28. #include "internal.h"
  29. #include "id3v2.h"
  30. #include "id3v1.h"
  31. #include "libavcodec/mpegaudiodecheader.h"
  32.  
  33. #define XING_FLAG_FRAMES 0x01
  34. #define XING_FLAG_SIZE   0x02
  35. #define XING_FLAG_TOC    0x04
  36.  
  37. #define XING_TOC_COUNT 100
  38.  
  39. typedef struct {
  40.     AVClass *class;
  41.     int64_t filesize;
  42.     int64_t header_filesize;
  43.     int xing_toc;
  44.     int start_pad;
  45.     int end_pad;
  46.     int usetoc;
  47.     int is_cbr;
  48. } MP3DecContext;
  49.  
  50. /* mp3 read */
  51.  
  52. static int mp3_read_probe(AVProbeData *p)
  53. {
  54.     int max_frames, first_frames = 0;
  55.     int fsize, frames, sample_rate;
  56.     uint32_t header;
  57.     const uint8_t *buf, *buf0, *buf2, *end;
  58.     AVCodecContext avctx;
  59.  
  60.     buf0 = p->buf;
  61.     end = p->buf + p->buf_size - sizeof(uint32_t);
  62.     while(buf0 < end && !*buf0)
  63.         buf0++;
  64.  
  65.     max_frames = 0;
  66.     buf = buf0;
  67.  
  68.     for(; buf < end; buf= buf2+1) {
  69.         buf2 = buf;
  70.  
  71.         for(frames = 0; buf2 < end; frames++) {
  72.             header = AV_RB32(buf2);
  73.             fsize = avpriv_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);
  74.             if(fsize < 0)
  75.                 break;
  76.             buf2 += fsize;
  77.         }
  78.         max_frames = FFMAX(max_frames, frames);
  79.         if(buf == buf0)
  80.             first_frames= frames;
  81.     }
  82.     // keep this in sync with ac3 probe, both need to avoid
  83.     // issues with MPEG-files!
  84.     if   (first_frames>=4) return AVPROBE_SCORE_EXTENSION + 1;
  85.     else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;
  86.     else if(max_frames>=4) return AVPROBE_SCORE_EXTENSION / 2;
  87.     else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)
  88.                            return p->buf_size < PROBE_BUF_MAX ? AVPROBE_SCORE_EXTENSION / 4 : AVPROBE_SCORE_EXTENSION - 2;
  89.     else if(max_frames>=1) return 1;
  90.     else                   return 0;
  91. //mpegps_mp3_unrecognized_format.mpg has max_frames=3
  92. }
  93.  
  94. static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
  95. {
  96.     int i;
  97.     MP3DecContext *mp3 = s->priv_data;
  98.     int fill_index = mp3->usetoc && duration > 0;
  99.  
  100.     if (!filesize &&
  101.         !(filesize = avio_size(s->pb))) {
  102.         av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
  103.         fill_index = 0;
  104.     }
  105.  
  106.     for (i = 0; i < XING_TOC_COUNT; i++) {
  107.         uint8_t b = avio_r8(s->pb);
  108.         if (fill_index)
  109.             av_add_index_entry(s->streams[0],
  110.                            av_rescale(b, filesize, 256),
  111.                            av_rescale(i, duration, XING_TOC_COUNT),
  112.                            0, 0, AVINDEX_KEYFRAME);
  113.     }
  114.     if (fill_index)
  115.         mp3->xing_toc = 1;
  116. }
  117.  
  118. /**
  119.  * Try to find Xing/Info/VBRI tags and compute duration from info therein
  120.  */
  121. static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
  122. {
  123.     MP3DecContext *mp3 = s->priv_data;
  124.     uint32_t v, spf;
  125.     unsigned frames = 0; /* Total number of frames in file */
  126.     unsigned size = 0; /* Total number of bytes in the stream */
  127.     static const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
  128.     MPADecodeHeader c;
  129.     int vbrtag_size = 0;
  130.     int is_cbr;
  131.  
  132.     v = avio_rb32(s->pb);
  133.     if(ff_mpa_check_header(v) < 0)
  134.       return -1;
  135.  
  136.     if (avpriv_mpegaudio_decode_header(&c, v) == 0)
  137.         vbrtag_size = c.frame_size;
  138.     if(c.layer != 3)
  139.         return -1;
  140.  
  141.     spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
  142.  
  143.     /* Check for Xing / Info tag */
  144.     avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
  145.     v = avio_rb32(s->pb);
  146.     is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
  147.     if (v == MKBETAG('X', 'i', 'n', 'g') || is_cbr) {
  148.         v = avio_rb32(s->pb);
  149.         if(v & XING_FLAG_FRAMES)
  150.             frames = avio_rb32(s->pb);
  151.         if(v & XING_FLAG_SIZE)
  152.             size = avio_rb32(s->pb);
  153.         if (v & XING_FLAG_TOC)
  154.             read_xing_toc(s, size, av_rescale_q(frames, (AVRational){spf, c.sample_rate},
  155.                                     st->time_base));
  156.         if(v & 8)
  157.             avio_skip(s->pb, 4);
  158.  
  159.         v = avio_rb32(s->pb);
  160.         if(v == MKBETAG('L', 'A', 'M', 'E') || v == MKBETAG('L', 'a', 'v', 'f')) {
  161.             avio_skip(s->pb, 21-4);
  162.             v= avio_rb24(s->pb);
  163.             mp3->start_pad = v>>12;
  164.             mp3->  end_pad = v&4095;
  165.             st->skip_samples = mp3->start_pad + 528 + 1;
  166.             av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3->  end_pad);
  167.         }
  168.     }
  169.  
  170.     /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
  171.     avio_seek(s->pb, base + 4 + 32, SEEK_SET);
  172.     v = avio_rb32(s->pb);
  173.     if(v == MKBETAG('V', 'B', 'R', 'I')) {
  174.         /* Check tag version */
  175.         if(avio_rb16(s->pb) == 1) {
  176.             /* skip delay and quality */
  177.             avio_skip(s->pb, 4);
  178.             size = avio_rb32(s->pb);
  179.             frames = avio_rb32(s->pb);
  180.         }
  181.     }
  182.  
  183.     if(!frames && !size)
  184.         return -1;
  185.  
  186.     /* Skip the vbr tag frame */
  187.     avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
  188.  
  189.     if(frames)
  190.         st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
  191.                                     st->time_base);
  192.     if (size && frames && !is_cbr)
  193.         st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
  194.  
  195.     mp3->is_cbr          = is_cbr;
  196.     mp3->header_filesize = size;
  197.  
  198.     return 0;
  199. }
  200.  
  201. static int mp3_read_header(AVFormatContext *s)
  202. {
  203.     MP3DecContext *mp3 = s->priv_data;
  204.     AVStream *st;
  205.     int64_t off;
  206.  
  207.     st = avformat_new_stream(s, NULL);
  208.     if (!st)
  209.         return AVERROR(ENOMEM);
  210.  
  211.     st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
  212.     st->codec->codec_id = AV_CODEC_ID_MP3;
  213.     st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
  214.     st->start_time = 0;
  215.  
  216.     // lcm of all mp3 sample rates
  217.     avpriv_set_pts_info(st, 64, 1, 14112000);
  218.  
  219.     s->pb->maxsize = -1;
  220.     off = avio_tell(s->pb);
  221.  
  222.     if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
  223.         ff_id3v1_read(s);
  224.  
  225.     if(s->pb->seekable)
  226.         mp3->filesize = avio_size(s->pb);
  227.  
  228.     if (mp3_parse_vbr_tags(s, st, off) < 0)
  229.         avio_seek(s->pb, off, SEEK_SET);
  230.  
  231.     /* the parameters will be extracted from the compressed bitstream */
  232.     return 0;
  233. }
  234.  
  235. #define MP3_PACKET_SIZE 1024
  236.  
  237. static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
  238. {
  239.     MP3DecContext *mp3 = s->priv_data;
  240.     int ret, size;
  241.     int64_t pos;
  242.  
  243.     size= MP3_PACKET_SIZE;
  244.     pos = avio_tell(s->pb);
  245.     if(mp3->filesize > ID3v1_TAG_SIZE && pos < mp3->filesize)
  246.         size= FFMIN(size, mp3->filesize - pos);
  247.  
  248.     ret= av_get_packet(s->pb, pkt, size);
  249.     if (ret <= 0) {
  250.         if(ret<0)
  251.             return ret;
  252.         return AVERROR_EOF;
  253.     }
  254.  
  255.     pkt->flags &= ~AV_PKT_FLAG_CORRUPT;
  256.     pkt->stream_index = 0;
  257.  
  258.     if (ret >= ID3v1_TAG_SIZE &&
  259.         memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
  260.         ret -= ID3v1_TAG_SIZE;
  261.  
  262.     /* note: we need to modify the packet size here to handle the last
  263.        packet */
  264.     pkt->size = ret;
  265.     return ret;
  266. }
  267.  
  268. static int check(AVFormatContext *s, int64_t pos)
  269. {
  270.     int64_t ret = avio_seek(s->pb, pos, SEEK_SET);
  271.     unsigned header;
  272.     MPADecodeHeader sd;
  273.     if (ret < 0)
  274.         return ret;
  275.     header = avio_rb32(s->pb);
  276.     if (ff_mpa_check_header(header) < 0)
  277.         return -1;
  278.     if (avpriv_mpegaudio_decode_header(&sd, header) == 1)
  279.         return -1;
  280.     return sd.frame_size;
  281. }
  282.  
  283. static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
  284.                     int flags)
  285. {
  286.     MP3DecContext *mp3 = s->priv_data;
  287.     AVIndexEntry *ie, ie1;
  288.     AVStream *st = s->streams[0];
  289.     int64_t ret  = av_index_search_timestamp(st, timestamp, flags);
  290.     int i, j;
  291.     int dir = (flags&AVSEEK_FLAG_BACKWARD) ? -1 : 1;
  292.  
  293.     if (mp3->is_cbr && st->duration > 0 && mp3->header_filesize > s->data_offset) {
  294.         int64_t filesize = avio_size(s->pb);
  295.         int64_t duration;
  296.         if (filesize <= s->data_offset)
  297.             filesize = mp3->header_filesize;
  298.         filesize -= s->data_offset;
  299.         duration = av_rescale(st->duration, filesize, mp3->header_filesize - s->data_offset);
  300.         ie = &ie1;
  301.         timestamp = av_clip64(timestamp, 0, duration);
  302.         ie->timestamp = timestamp;
  303.         ie->pos       = av_rescale(timestamp, filesize, duration) + s->data_offset;
  304.     } else if (mp3->xing_toc) {
  305.         if (ret < 0)
  306.             return ret;
  307.  
  308.         ie = &st->index_entries[ret];
  309.     } else {
  310.         st->skip_samples = timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;
  311.  
  312.         return -1;
  313.     }
  314.  
  315.     ret = avio_seek(s->pb, ie->pos, SEEK_SET);
  316.     if (ret < 0)
  317.         return ret;
  318.  
  319. #define MIN_VALID 3
  320.     for(i=0; i<4096; i++) {
  321.         int64_t pos = ie->pos + i*dir;
  322.         for(j=0; j<MIN_VALID; j++) {
  323.             ret = check(s, pos);
  324.             if(ret < 0)
  325.                 break;
  326.             pos += ret;
  327.         }
  328.         if(j==MIN_VALID)
  329.             break;
  330.     }
  331.     if(j!=MIN_VALID)
  332.         i=0;
  333.  
  334.     ret = avio_seek(s->pb, ie->pos + i*dir, SEEK_SET);
  335.     if (ret < 0)
  336.         return ret;
  337.     ff_update_cur_dts(s, st, ie->timestamp);
  338.     st->skip_samples = ie->timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;
  339.     return 0;
  340. }
  341.  
  342. static const AVOption options[] = {
  343.     { "usetoc", "use table of contents", offsetof(MP3DecContext, usetoc), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 1, AV_OPT_FLAG_DECODING_PARAM},
  344.     { NULL },
  345. };
  346.  
  347. static const AVClass demuxer_class = {
  348.     .class_name = "mp3",
  349.     .item_name  = av_default_item_name,
  350.     .option     = options,
  351.     .version    = LIBAVUTIL_VERSION_INT,
  352.     .category   = AV_CLASS_CATEGORY_DEMUXER,
  353. };
  354.  
  355. AVInputFormat ff_mp3_demuxer = {
  356.     .name           = "mp3",
  357.     .long_name      = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
  358.     .read_probe     = mp3_read_probe,
  359.     .read_header    = mp3_read_header,
  360.     .read_packet    = mp3_read_packet,
  361.     .read_seek      = mp3_seek,
  362.     .priv_data_size = sizeof(MP3DecContext),
  363.     .flags          = AVFMT_GENERIC_INDEX,
  364.     .extensions     = "mp2,mp3,m2a,mpa", /* XXX: use probe */
  365.     .priv_class     = &demuxer_class,
  366. };
  367.