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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.  
  35. #include "libavcodec/avcodec.h"
  36. #include "libavcodec/mpegaudiodecheader.h"
  37.  
  38. #define XING_FLAG_FRAMES 0x01
  39. #define XING_FLAG_SIZE   0x02
  40. #define XING_FLAG_TOC    0x04
  41. #define XING_FLAC_QSCALE 0x08
  42.  
  43. #define XING_TOC_COUNT 100
  44.  
  45. #define SAME_HEADER_MASK \
  46.    (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
  47.  
  48. typedef struct {
  49.     AVClass *class;
  50.     int64_t filesize;
  51.     int xing_toc;
  52.     int start_pad;
  53.     int end_pad;
  54.     int usetoc;
  55.     unsigned frames; /* Total number of frames in file */
  56.     unsigned header_filesize;   /* Total number of bytes in the stream */
  57.     int is_cbr;
  58. } MP3DecContext;
  59.  
  60. static int check(AVIOContext *pb, int64_t pos, uint32_t *header);
  61.  
  62. /* mp3 read */
  63.  
  64. static int mp3_read_probe(AVProbeData *p)
  65. {
  66.     int max_frames, first_frames = 0;
  67.     int fsize, frames;
  68.     uint32_t header;
  69.     const uint8_t *buf, *buf0, *buf2, *end;
  70.     AVCodecContext *avctx = avcodec_alloc_context3(NULL);
  71.  
  72.     if (!avctx)
  73.         return AVERROR(ENOMEM);
  74.  
  75.     buf0 = p->buf;
  76.     end = p->buf + p->buf_size - sizeof(uint32_t);
  77.     while(buf0 < end && !*buf0)
  78.         buf0++;
  79.  
  80.     max_frames = 0;
  81.     buf = buf0;
  82.  
  83.     for(; buf < end; buf= buf2+1) {
  84.         buf2 = buf;
  85.         if(ff_mpa_check_header(AV_RB32(buf2)))
  86.             continue;
  87.  
  88.         for(frames = 0; buf2 < end; frames++) {
  89.             int dummy;
  90.             header = AV_RB32(buf2);
  91.             fsize = avpriv_mpa_decode_header(avctx, header,
  92.                                              &dummy, &dummy, &dummy, &dummy);
  93.             if(fsize < 0)
  94.                 break;
  95.             buf2 += fsize;
  96.         }
  97.         max_frames = FFMAX(max_frames, frames);
  98.         if(buf == buf0)
  99.             first_frames= frames;
  100.     }
  101.     avcodec_free_context(&avctx);
  102.     // keep this in sync with ac3 probe, both need to avoid
  103.     // issues with MPEG-files!
  104.     if   (first_frames>=7) return AVPROBE_SCORE_EXTENSION + 1;
  105.     else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;
  106.     else if(max_frames>=4 && max_frames >= p->buf_size/10000) return AVPROBE_SCORE_EXTENSION / 2;
  107.     else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)
  108.                            return p->buf_size < PROBE_BUF_MAX ? AVPROBE_SCORE_EXTENSION / 4 : AVPROBE_SCORE_EXTENSION - 2;
  109.     else if(max_frames>=1 && max_frames >= p->buf_size/10000) return 1;
  110.     else                   return 0;
  111. //mpegps_mp3_unrecognized_format.mpg has max_frames=3
  112. }
  113.  
  114. static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
  115. {
  116.     int i;
  117.     MP3DecContext *mp3 = s->priv_data;
  118.     int fill_index = mp3->usetoc == 1 && duration > 0;
  119.  
  120.     if (!filesize &&
  121.         !(filesize = avio_size(s->pb))) {
  122.         av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
  123.         fill_index = 0;
  124.     }
  125.  
  126.     for (i = 0; i < XING_TOC_COUNT; i++) {
  127.         uint8_t b = avio_r8(s->pb);
  128.         if (fill_index)
  129.             av_add_index_entry(s->streams[0],
  130.                            av_rescale(b, filesize, 256),
  131.                            av_rescale(i, duration, XING_TOC_COUNT),
  132.                            0, 0, AVINDEX_KEYFRAME);
  133.     }
  134.     if (fill_index)
  135.         mp3->xing_toc = 1;
  136. }
  137.  
  138. static void mp3_parse_info_tag(AVFormatContext *s, AVStream *st,
  139.                                MPADecodeHeader *c, uint32_t spf)
  140. {
  141. #define LAST_BITS(k, n) ((k) & ((1 << (n)) - 1))
  142. #define MIDDLE_BITS(k, m, n) LAST_BITS((k) >> (m), ((n) - (m)))
  143.  
  144.     uint16_t crc;
  145.     uint32_t v;
  146.  
  147.     char version[10];
  148.  
  149.     uint32_t peak   = 0;
  150.     int32_t  r_gain = INT32_MIN, a_gain = INT32_MIN;
  151.  
  152.     MP3DecContext *mp3 = s->priv_data;
  153.     static const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
  154.     uint64_t fsize = avio_size(s->pb);
  155.     fsize = fsize >= avio_tell(s->pb) ? fsize - avio_tell(s->pb) : 0;
  156.  
  157.     /* Check for Xing / Info tag */
  158.     avio_skip(s->pb, xing_offtbl[c->lsf == 1][c->nb_channels == 1]);
  159.     v = avio_rb32(s->pb);
  160.     mp3->is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
  161.     if (v != MKBETAG('X', 'i', 'n', 'g') && !mp3->is_cbr)
  162.         return;
  163.  
  164.     v = avio_rb32(s->pb);
  165.     if (v & XING_FLAG_FRAMES)
  166.         mp3->frames = avio_rb32(s->pb);
  167.     if (v & XING_FLAG_SIZE)
  168.         mp3->header_filesize = avio_rb32(s->pb);
  169.     if (fsize && mp3->header_filesize) {
  170.         uint64_t min, delta;
  171.         min = FFMIN(fsize, mp3->header_filesize);
  172.         delta = FFMAX(fsize, mp3->header_filesize) - min;
  173.         if (fsize > mp3->header_filesize && delta > min >> 4) {
  174.             mp3->frames = 0;
  175.             av_log(s, AV_LOG_WARNING,
  176.                    "invalid concatenated file detected - using bitrate for duration\n");
  177.         } else if (delta > min >> 4) {
  178.             av_log(s, AV_LOG_WARNING,
  179.                    "filesize and duration do not match (growing file?)\n");
  180.         }
  181.     }
  182.     if (v & XING_FLAG_TOC)
  183.         read_xing_toc(s, mp3->header_filesize, av_rescale_q(mp3->frames,
  184.                                        (AVRational){spf, c->sample_rate},
  185.                                        st->time_base));
  186.     /* VBR quality */
  187.     if (v & XING_FLAC_QSCALE)
  188.         avio_rb32(s->pb);
  189.  
  190.     /* Encoder short version string */
  191.     memset(version, 0, sizeof(version));
  192.     avio_read(s->pb, version, 9);
  193.  
  194.     /* Info Tag revision + VBR method */
  195.     avio_r8(s->pb);
  196.  
  197.     /* Lowpass filter value */
  198.     avio_r8(s->pb);
  199.  
  200.     /* ReplayGain peak */
  201.     v    = avio_rb32(s->pb);
  202.     peak = av_rescale(v, 100000, 1 << 23);
  203.  
  204.     /* Radio ReplayGain */
  205.     v = avio_rb16(s->pb);
  206.  
  207.     if (MIDDLE_BITS(v, 13, 15) == 1) {
  208.         r_gain = MIDDLE_BITS(v, 0, 8) * 10000;
  209.  
  210.         if (v & (1 << 9))
  211.             r_gain *= -1;
  212.     }
  213.  
  214.     /* Audiophile ReplayGain */
  215.     v = avio_rb16(s->pb);
  216.  
  217.     if (MIDDLE_BITS(v, 13, 15) == 2) {
  218.         a_gain = MIDDLE_BITS(v, 0, 8) * 10000;
  219.  
  220.         if (v & (1 << 9))
  221.             a_gain *= -1;
  222.     }
  223.  
  224.     /* Encoding flags + ATH Type */
  225.     avio_r8(s->pb);
  226.  
  227.     /* if ABR {specified bitrate} else {minimal bitrate} */
  228.     avio_r8(s->pb);
  229.  
  230.     /* Encoder delays */
  231.     v= avio_rb24(s->pb);
  232.     if(AV_RB32(version) == MKBETAG('L', 'A', 'M', 'E')
  233.         || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'f')
  234.         || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'c')
  235.     ) {
  236.  
  237.         mp3->start_pad = v>>12;
  238.         mp3->  end_pad = v&4095;
  239.         st->start_skip_samples = mp3->start_pad + 528 + 1;
  240.         if (mp3->frames) {
  241.             st->first_discard_sample = -mp3->end_pad + 528 + 1 + mp3->frames * (int64_t)spf;
  242.             st->last_discard_sample = mp3->frames * (int64_t)spf;
  243.         }
  244.         if (!st->start_time)
  245.             st->start_time = av_rescale_q(st->start_skip_samples,
  246.                                             (AVRational){1, c->sample_rate},
  247.                                             st->time_base);
  248.         av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3->  end_pad);
  249.     }
  250.  
  251.     /* Misc */
  252.     avio_r8(s->pb);
  253.  
  254.     /* MP3 gain */
  255.     avio_r8(s->pb);
  256.  
  257.     /* Preset and surround info */
  258.     avio_rb16(s->pb);
  259.  
  260.     /* Music length */
  261.     avio_rb32(s->pb);
  262.  
  263.     /* Music CRC */
  264.     avio_rb16(s->pb);
  265.  
  266.     /* Info Tag CRC */
  267.     crc = ffio_get_checksum(s->pb);
  268.     v   = avio_rb16(s->pb);
  269.  
  270.     if (v == crc) {
  271.         ff_replaygain_export_raw(st, r_gain, peak, a_gain, 0);
  272.         av_dict_set(&st->metadata, "encoder", version, 0);
  273.     }
  274. }
  275.  
  276. static void mp3_parse_vbri_tag(AVFormatContext *s, AVStream *st, int64_t base)
  277. {
  278.     uint32_t v;
  279.     MP3DecContext *mp3 = s->priv_data;
  280.  
  281.     /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
  282.     avio_seek(s->pb, base + 4 + 32, SEEK_SET);
  283.     v = avio_rb32(s->pb);
  284.     if (v == MKBETAG('V', 'B', 'R', 'I')) {
  285.         /* Check tag version */
  286.         if (avio_rb16(s->pb) == 1) {
  287.             /* skip delay and quality */
  288.             avio_skip(s->pb, 4);
  289.             mp3->header_filesize = avio_rb32(s->pb);
  290.             mp3->frames = avio_rb32(s->pb);
  291.         }
  292.     }
  293. }
  294.  
  295. /**
  296.  * Try to find Xing/Info/VBRI tags and compute duration from info therein
  297.  */
  298. static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
  299. {
  300.     uint32_t v, spf;
  301.     MPADecodeHeader c;
  302.     int vbrtag_size = 0;
  303.     MP3DecContext *mp3 = s->priv_data;
  304.  
  305.     ffio_init_checksum(s->pb, ff_crcA001_update, 0);
  306.  
  307.     v = avio_rb32(s->pb);
  308.     if(ff_mpa_check_header(v) < 0)
  309.       return -1;
  310.  
  311.     if (avpriv_mpegaudio_decode_header(&c, v) == 0)
  312.         vbrtag_size = c.frame_size;
  313.     if(c.layer != 3)
  314.         return -1;
  315.  
  316.     spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
  317.  
  318.     mp3->frames = 0;
  319.     mp3->header_filesize   = 0;
  320.  
  321.     mp3_parse_info_tag(s, st, &c, spf);
  322.     mp3_parse_vbri_tag(s, st, base);
  323.  
  324.     if (!mp3->frames && !mp3->header_filesize)
  325.         return -1;
  326.  
  327.     /* Skip the vbr tag frame */
  328.     avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
  329.  
  330.     if (mp3->frames)
  331.         st->duration = av_rescale_q(mp3->frames, (AVRational){spf, c.sample_rate},
  332.                                     st->time_base);
  333.     if (mp3->header_filesize && mp3->frames && !mp3->is_cbr)
  334.         st->codec->bit_rate = av_rescale(mp3->header_filesize, 8 * c.sample_rate, mp3->frames * (int64_t)spf);
  335.  
  336.     return 0;
  337. }
  338.  
  339. static int mp3_read_header(AVFormatContext *s)
  340. {
  341.     MP3DecContext *mp3 = s->priv_data;
  342.     AVStream *st;
  343.     int64_t off;
  344.     int ret;
  345.     int i;
  346.  
  347.     if (mp3->usetoc < 0)
  348.         mp3->usetoc = (s->flags & AVFMT_FLAG_FAST_SEEK) ? 0 : 2;
  349.  
  350.     st = avformat_new_stream(s, NULL);
  351.     if (!st)
  352.         return AVERROR(ENOMEM);
  353.  
  354.     st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
  355.     st->codec->codec_id = AV_CODEC_ID_MP3;
  356.     st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
  357.     st->start_time = 0;
  358.  
  359.     // lcm of all mp3 sample rates
  360.     avpriv_set_pts_info(st, 64, 1, 14112000);
  361.  
  362.     s->pb->maxsize = -1;
  363.     off = avio_tell(s->pb);
  364.  
  365.     if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
  366.         ff_id3v1_read(s);
  367.  
  368.     if(s->pb->seekable)
  369.         mp3->filesize = avio_size(s->pb);
  370.  
  371.     if (mp3_parse_vbr_tags(s, st, off) < 0)
  372.         avio_seek(s->pb, off, SEEK_SET);
  373.  
  374.     ret = ff_replaygain_export(st, s->metadata);
  375.     if (ret < 0)
  376.         return ret;
  377.  
  378.     off = avio_tell(s->pb);
  379.     for (i = 0; i < 64 * 1024; i++) {
  380.         uint32_t header, header2;
  381.         int frame_size;
  382.         if (!(i&1023))
  383.             ffio_ensure_seekback(s->pb, i + 1024 + 4);
  384.         frame_size = check(s->pb, off + i, &header);
  385.         if (frame_size > 0) {
  386.             avio_seek(s->pb, off, SEEK_SET);
  387.             ffio_ensure_seekback(s->pb, i + 1024 + frame_size + 4);
  388.             if (check(s->pb, off + i + frame_size, &header2) >= 0 &&
  389.                 (header & SAME_HEADER_MASK) == (header2 & SAME_HEADER_MASK))
  390.             {
  391.                 av_log(s, AV_LOG_INFO, "Skipping %d bytes of junk at %"PRId64".\n", i, off);
  392.                 avio_seek(s->pb, off + i, SEEK_SET);
  393.                 break;
  394.             }
  395.         }
  396.         avio_seek(s->pb, off, SEEK_SET);
  397.     }
  398.  
  399.     // the seek index is relative to the end of the xing vbr headers
  400.     for (i = 0; i < st->nb_index_entries; i++)
  401.         st->index_entries[i].pos += avio_tell(s->pb);
  402.  
  403.     /* the parameters will be extracted from the compressed bitstream */
  404.     return 0;
  405. }
  406.  
  407. #define MP3_PACKET_SIZE 1024
  408.  
  409. static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
  410. {
  411.     MP3DecContext *mp3 = s->priv_data;
  412.     int ret, size;
  413.     int64_t pos;
  414.  
  415.     size= MP3_PACKET_SIZE;
  416.     pos = avio_tell(s->pb);
  417.     if(mp3->filesize > ID3v1_TAG_SIZE && pos < mp3->filesize)
  418.         size= FFMIN(size, mp3->filesize - pos);
  419.  
  420.     ret= av_get_packet(s->pb, pkt, size);
  421.     if (ret <= 0) {
  422.         if(ret<0)
  423.             return ret;
  424.         return AVERROR_EOF;
  425.     }
  426.  
  427.     pkt->flags &= ~AV_PKT_FLAG_CORRUPT;
  428.     pkt->stream_index = 0;
  429.  
  430.     return ret;
  431. }
  432.  
  433. #define SEEK_WINDOW 4096
  434.  
  435. static int check(AVIOContext *pb, int64_t pos, uint32_t *ret_header)
  436. {
  437.     int64_t ret = avio_seek(pb, pos, SEEK_SET);
  438.     unsigned header;
  439.     MPADecodeHeader sd;
  440.     if (ret < 0)
  441.         return ret;
  442.  
  443.     header = avio_rb32(pb);
  444.     if (ff_mpa_check_header(header) < 0)
  445.         return -1;
  446.     if (avpriv_mpegaudio_decode_header(&sd, header) == 1)
  447.         return -1;
  448.  
  449.     if (ret_header)
  450.         *ret_header = header;
  451.     return sd.frame_size;
  452. }
  453.  
  454. static int64_t mp3_sync(AVFormatContext *s, int64_t target_pos, int flags)
  455. {
  456.     int dir = (flags&AVSEEK_FLAG_BACKWARD) ? -1 : 1;
  457.     int64_t best_pos;
  458.     int best_score, i, j;
  459.     int64_t ret;
  460.  
  461.     avio_seek(s->pb, FFMAX(target_pos - SEEK_WINDOW, 0), SEEK_SET);
  462.     ret = avio_seek(s->pb, target_pos, SEEK_SET);
  463.     if (ret < 0)
  464.         return ret;
  465.  
  466. #define MIN_VALID 3
  467.     best_pos = target_pos;
  468.     best_score = 999;
  469.     for(i=0; i<SEEK_WINDOW; i++) {
  470.         int64_t pos = target_pos + (dir > 0 ? i - SEEK_WINDOW/4 : -i);
  471.         int64_t candidate = -1;
  472.         int score = 999;
  473.  
  474.         if (pos < 0)
  475.             continue;
  476.  
  477.         for(j=0; j<MIN_VALID; j++) {
  478.             ret = check(s->pb, pos, NULL);
  479.             if(ret < 0)
  480.                 break;
  481.             if ((target_pos - pos)*dir <= 0 && abs(MIN_VALID/2-j) < score) {
  482.                 candidate = pos;
  483.                 score = abs(MIN_VALID/2-j);
  484.             }
  485.             pos += ret;
  486.         }
  487.         if (best_score > score && j == MIN_VALID) {
  488.             best_pos = candidate;
  489.             best_score = score;
  490.             if(score == 0)
  491.                 break;
  492.         }
  493.     }
  494.  
  495.     return avio_seek(s->pb, best_pos, SEEK_SET);
  496. }
  497.  
  498. static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
  499.                     int flags)
  500. {
  501.     MP3DecContext *mp3 = s->priv_data;
  502.     AVIndexEntry *ie, ie1;
  503.     AVStream *st = s->streams[0];
  504.     int64_t ret  = av_index_search_timestamp(st, timestamp, flags);
  505.     int64_t best_pos;
  506.  
  507.     if (mp3->usetoc == 2)
  508.         return -1; // generic index code
  509.  
  510.     if (   mp3->is_cbr
  511.         && (mp3->usetoc == 0 || !mp3->xing_toc)
  512.         && st->duration > 0
  513.         && mp3->header_filesize > s->internal->data_offset
  514.         && mp3->frames) {
  515.         ie = &ie1;
  516.         timestamp = av_clip64(timestamp, 0, st->duration);
  517.         ie->timestamp = timestamp;
  518.         ie->pos       = av_rescale(timestamp, mp3->header_filesize, st->duration) + s->internal->data_offset;
  519.     } else if (mp3->xing_toc) {
  520.         if (ret < 0)
  521.             return ret;
  522.  
  523.         ie = &st->index_entries[ret];
  524.     } else {
  525.         return -1;
  526.     }
  527.  
  528.     best_pos = mp3_sync(s, ie->pos, flags);
  529.     if (best_pos < 0)
  530.         return best_pos;
  531.  
  532.     if (mp3->is_cbr && ie == &ie1) {
  533.         int frame_duration = av_rescale(st->duration, 1, mp3->frames);
  534.         ie1.timestamp = frame_duration * av_rescale(best_pos - s->internal->data_offset, mp3->frames, mp3->header_filesize);
  535.     }
  536.  
  537.     ff_update_cur_dts(s, st, ie->timestamp);
  538.     return 0;
  539. }
  540.  
  541. static const AVOption options[] = {
  542.     { "usetoc", "use table of contents", offsetof(MP3DecContext, usetoc), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 2, AV_OPT_FLAG_DECODING_PARAM},
  543.     { NULL },
  544. };
  545.  
  546. static const AVClass demuxer_class = {
  547.     .class_name = "mp3",
  548.     .item_name  = av_default_item_name,
  549.     .option     = options,
  550.     .version    = LIBAVUTIL_VERSION_INT,
  551.     .category   = AV_CLASS_CATEGORY_DEMUXER,
  552. };
  553.  
  554. AVInputFormat ff_mp3_demuxer = {
  555.     .name           = "mp3",
  556.     .long_name      = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
  557.     .read_probe     = mp3_read_probe,
  558.     .read_header    = mp3_read_header,
  559.     .read_packet    = mp3_read_packet,
  560.     .read_seek      = mp3_seek,
  561.     .priv_data_size = sizeof(MP3DecContext),
  562.     .flags          = AVFMT_GENERIC_INDEX,
  563.     .extensions     = "mp2,mp3,m2a,mpa", /* XXX: use probe */
  564.     .priv_class     = &demuxer_class,
  565. };
  566.