LCOV - code coverage report
Current view: top level - libavformat - mp3dec.c (source / functions) Hit Total Coverage
Test: coverage.info Lines: 254 296 85.8 %
Date: 2017-12-16 21:16:39 Functions: 10 10 100.0 %

          Line data    Source code
       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             : enum CheckRet {
      61             :     CHECK_WRONG_HEADER = -1,
      62             :     CHECK_SEEK_FAILED  = -2,
      63             : };
      64             : 
      65             : static int check(AVIOContext *pb, int64_t pos, uint32_t *header);
      66             : 
      67             : /* mp3 read */
      68             : 
      69        6130 : static int mp3_read_probe(AVProbeData *p)
      70             : {
      71        6130 :     int max_frames, first_frames = 0;
      72        6130 :     int whole_used = 0;
      73             :     int frames, ret;
      74             :     uint32_t header;
      75             :     const uint8_t *buf, *buf0, *buf2, *end;
      76             : 
      77        6130 :     buf0 = p->buf;
      78        6130 :     end = p->buf + p->buf_size - sizeof(uint32_t);
      79       74501 :     while(buf0 < end && !*buf0)
      80       62241 :         buf0++;
      81             : 
      82        6130 :     max_frames = 0;
      83        6130 :     buf = buf0;
      84             : 
      85   114744400 :     for(; buf < end; buf= buf2+1) {
      86   114738270 :         buf2 = buf;
      87   114771006 :         for(frames = 0; buf2 < end; frames++) {
      88             :             MPADecodeHeader h;
      89             : 
      90   114770371 :             header = AV_RB32(buf2);
      91   114770371 :             ret = avpriv_mpegaudio_decode_header(&h, header);
      92   114770371 :             if (ret != 0)
      93   114737635 :                 break;
      94       32736 :             buf2 += h.frame_size;
      95             :         }
      96   114738270 :         max_frames = FFMAX(max_frames, frames);
      97   114738270 :         if(buf == buf0) {
      98        6128 :             first_frames= frames;
      99        6128 :             if (buf2 == end + sizeof(uint32_t))
     100           1 :                 whole_used = 1;
     101             :         }
     102             :     }
     103             :     // keep this in sync with ac3 probe, both need to avoid
     104             :     // issues with MPEG-files!
     105        6130 :     if   (first_frames>=7) return AVPROBE_SCORE_EXTENSION + 1;
     106        6107 :     else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;
     107        6107 :     else if(max_frames>=4 && max_frames >= p->buf_size/10000) return AVPROBE_SCORE_EXTENSION / 2;
     108        6098 :     else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)
     109           5 :                            return p->buf_size < PROBE_BUF_MAX ? AVPROBE_SCORE_EXTENSION / 4 : AVPROBE_SCORE_EXTENSION - 2;
     110        6093 :     else if(first_frames > 1 && whole_used) return 5;
     111        6093 :     else if(max_frames>=1 && max_frames >= p->buf_size/10000) return 1;
     112        3931 :     else                   return 0;
     113             : //mpegps_mp3_unrecognized_format.mpg has max_frames=3
     114             : }
     115             : 
     116          10 : static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
     117             : {
     118             :     int i;
     119          10 :     MP3DecContext *mp3 = s->priv_data;
     120          10 :     int fast_seek = s->flags & AVFMT_FLAG_FAST_SEEK;
     121          10 :     int fill_index = (mp3->usetoc || fast_seek) && duration > 0;
     122             : 
     123          10 :     if (!filesize &&
     124           0 :         !(filesize = avio_size(s->pb))) {
     125           0 :         av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
     126           0 :         fill_index = 0;
     127             :     }
     128             : 
     129        1010 :     for (i = 0; i < XING_TOC_COUNT; i++) {
     130        1000 :         uint8_t b = avio_r8(s->pb);
     131        1000 :         if (fill_index)
     132         100 :             av_add_index_entry(s->streams[0],
     133             :                            av_rescale(b, filesize, 256),
     134             :                            av_rescale(i, duration, XING_TOC_COUNT),
     135             :                            0, 0, AVINDEX_KEYFRAME);
     136             :     }
     137          10 :     if (fill_index)
     138           1 :         mp3->xing_toc = 1;
     139          10 : }
     140             : 
     141          19 : static void mp3_parse_info_tag(AVFormatContext *s, AVStream *st,
     142             :                                MPADecodeHeader *c, uint32_t spf)
     143             : {
     144             : #define LAST_BITS(k, n) ((k) & ((1 << (n)) - 1))
     145             : #define MIDDLE_BITS(k, m, n) LAST_BITS((k) >> (m), ((n) - (m) + 1))
     146             : 
     147             :     uint16_t crc;
     148             :     uint32_t v;
     149             : 
     150             :     char version[10];
     151             : 
     152          19 :     uint32_t peak   = 0;
     153          19 :     int32_t  r_gain = INT32_MIN, a_gain = INT32_MIN;
     154             : 
     155          19 :     MP3DecContext *mp3 = s->priv_data;
     156             :     static const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
     157          19 :     uint64_t fsize = avio_size(s->pb);
     158          19 :     fsize = fsize >= avio_tell(s->pb) ? fsize - avio_tell(s->pb) : 0;
     159             : 
     160             :     /* Check for Xing / Info tag */
     161          19 :     avio_skip(s->pb, xing_offtbl[c->lsf == 1][c->nb_channels == 1]);
     162          19 :     v = avio_rb32(s->pb);
     163          19 :     mp3->is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
     164          19 :     if (v != MKBETAG('X', 'i', 'n', 'g') && !mp3->is_cbr)
     165           8 :         return;
     166             : 
     167          11 :     v = avio_rb32(s->pb);
     168          11 :     if (v & XING_FLAG_FRAMES)
     169          11 :         mp3->frames = avio_rb32(s->pb);
     170          11 :     if (v & XING_FLAG_SIZE)
     171          10 :         mp3->header_filesize = avio_rb32(s->pb);
     172          11 :     if (fsize && mp3->header_filesize) {
     173             :         uint64_t min, delta;
     174          10 :         min = FFMIN(fsize, mp3->header_filesize);
     175          10 :         delta = FFMAX(fsize, mp3->header_filesize) - min;
     176          10 :         if (fsize > mp3->header_filesize && delta > min >> 4) {
     177           0 :             mp3->frames = 0;
     178           0 :             av_log(s, AV_LOG_WARNING,
     179             :                    "invalid concatenated file detected - using bitrate for duration\n");
     180          10 :         } else if (delta > min >> 4) {
     181           0 :             av_log(s, AV_LOG_WARNING,
     182             :                    "filesize and duration do not match (growing file?)\n");
     183             :         }
     184             :     }
     185          11 :     if (v & XING_FLAG_TOC)
     186          10 :         read_xing_toc(s, mp3->header_filesize, av_rescale_q(mp3->frames,
     187          10 :                                        (AVRational){spf, c->sample_rate},
     188             :                                        st->time_base));
     189             :     /* VBR quality */
     190          11 :     if (v & XING_FLAC_QSCALE)
     191           9 :         avio_rb32(s->pb);
     192             : 
     193             :     /* Encoder short version string */
     194          11 :     memset(version, 0, sizeof(version));
     195          11 :     avio_read(s->pb, version, 9);
     196             : 
     197             :     /* Info Tag revision + VBR method */
     198          11 :     avio_r8(s->pb);
     199             : 
     200             :     /* Lowpass filter value */
     201          11 :     avio_r8(s->pb);
     202             : 
     203             :     /* ReplayGain peak */
     204          11 :     v    = avio_rb32(s->pb);
     205          11 :     peak = av_rescale(v, 100000, 1 << 23);
     206             : 
     207             :     /* Radio ReplayGain */
     208          11 :     v = avio_rb16(s->pb);
     209             : 
     210          11 :     if (MIDDLE_BITS(v, 13, 15) == 1) {
     211           0 :         r_gain = MIDDLE_BITS(v, 0, 8) * 10000;
     212             : 
     213           0 :         if (v & (1 << 9))
     214           0 :             r_gain *= -1;
     215             :     }
     216             : 
     217             :     /* Audiophile ReplayGain */
     218          11 :     v = avio_rb16(s->pb);
     219             : 
     220          11 :     if (MIDDLE_BITS(v, 13, 15) == 2) {
     221           0 :         a_gain = MIDDLE_BITS(v, 0, 8) * 10000;
     222             : 
     223           0 :         if (v & (1 << 9))
     224           0 :             a_gain *= -1;
     225             :     }
     226             : 
     227             :     /* Encoding flags + ATH Type */
     228          11 :     avio_r8(s->pb);
     229             : 
     230             :     /* if ABR {specified bitrate} else {minimal bitrate} */
     231          11 :     avio_r8(s->pb);
     232             : 
     233             :     /* Encoder delays */
     234          11 :     v= avio_rb24(s->pb);
     235          11 :     if(AV_RB32(version) == MKBETAG('L', 'A', 'M', 'E')
     236           3 :         || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'f')
     237           1 :         || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'c')
     238             :     ) {
     239             : 
     240          10 :         mp3->start_pad = v>>12;
     241          10 :         mp3->  end_pad = v&4095;
     242          10 :         st->start_skip_samples = mp3->start_pad + 528 + 1;
     243          10 :         if (mp3->frames) {
     244          10 :             st->first_discard_sample = -mp3->end_pad + 528 + 1 + mp3->frames * (int64_t)spf;
     245          10 :             st->last_discard_sample = mp3->frames * (int64_t)spf;
     246             :         }
     247          10 :         if (!st->start_time)
     248          10 :             st->start_time = av_rescale_q(st->start_skip_samples,
     249          10 :                                             (AVRational){1, c->sample_rate},
     250             :                                             st->time_base);
     251          10 :         av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3->  end_pad);
     252             :     }
     253             : 
     254             :     /* Misc */
     255          11 :     avio_r8(s->pb);
     256             : 
     257             :     /* MP3 gain */
     258          11 :     avio_r8(s->pb);
     259             : 
     260             :     /* Preset and surround info */
     261          11 :     avio_rb16(s->pb);
     262             : 
     263             :     /* Music length */
     264          11 :     avio_rb32(s->pb);
     265             : 
     266             :     /* Music CRC */
     267          11 :     avio_rb16(s->pb);
     268             : 
     269             :     /* Info Tag CRC */
     270          11 :     crc = ffio_get_checksum(s->pb);
     271          11 :     v   = avio_rb16(s->pb);
     272             : 
     273          11 :     if (v == crc) {
     274           8 :         ff_replaygain_export_raw(st, r_gain, peak, a_gain, 0);
     275           8 :         av_dict_set(&st->metadata, "encoder", version, 0);
     276             :     }
     277             : }
     278             : 
     279          19 : static void mp3_parse_vbri_tag(AVFormatContext *s, AVStream *st, int64_t base)
     280             : {
     281             :     uint32_t v;
     282          19 :     MP3DecContext *mp3 = s->priv_data;
     283             : 
     284             :     /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
     285          19 :     avio_seek(s->pb, base + 4 + 32, SEEK_SET);
     286          19 :     v = avio_rb32(s->pb);
     287          19 :     if (v == MKBETAG('V', 'B', 'R', 'I')) {
     288             :         /* Check tag version */
     289           0 :         if (avio_rb16(s->pb) == 1) {
     290             :             /* skip delay and quality */
     291           0 :             avio_skip(s->pb, 4);
     292           0 :             mp3->header_filesize = avio_rb32(s->pb);
     293           0 :             mp3->frames = avio_rb32(s->pb);
     294             :         }
     295             :     }
     296          19 : }
     297             : 
     298             : /**
     299             :  * Try to find Xing/Info/VBRI tags and compute duration from info therein
     300             :  */
     301          23 : static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
     302             : {
     303             :     uint32_t v, spf;
     304             :     MPADecodeHeader c;
     305          23 :     int vbrtag_size = 0;
     306          23 :     MP3DecContext *mp3 = s->priv_data;
     307             :     int ret;
     308             : 
     309          23 :     ffio_init_checksum(s->pb, ff_crcA001_update, 0);
     310             : 
     311          23 :     v = avio_rb32(s->pb);
     312             : 
     313          23 :     ret = avpriv_mpegaudio_decode_header(&c, v);
     314          23 :     if (ret < 0)
     315           1 :         return ret;
     316          22 :     else if (ret == 0)
     317          22 :         vbrtag_size = c.frame_size;
     318          22 :     if(c.layer != 3)
     319           3 :         return -1;
     320             : 
     321          19 :     spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
     322             : 
     323          19 :     mp3->frames = 0;
     324          19 :     mp3->header_filesize   = 0;
     325             : 
     326          19 :     mp3_parse_info_tag(s, st, &c, spf);
     327          19 :     mp3_parse_vbri_tag(s, st, base);
     328             : 
     329          19 :     if (!mp3->frames && !mp3->header_filesize)
     330           8 :         return -1;
     331             : 
     332             :     /* Skip the vbr tag frame */
     333          11 :     avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
     334             : 
     335          11 :     if (mp3->frames)
     336          11 :         st->duration = av_rescale_q(mp3->frames, (AVRational){spf, c.sample_rate},
     337             :                                     st->time_base);
     338          11 :     if (mp3->header_filesize && mp3->frames && !mp3->is_cbr)
     339           1 :         st->codecpar->bit_rate = av_rescale(mp3->header_filesize, 8 * c.sample_rate, mp3->frames * (int64_t)spf);
     340             : 
     341          11 :     return 0;
     342             : }
     343             : 
     344          23 : static int mp3_read_header(AVFormatContext *s)
     345             : {
     346          23 :     MP3DecContext *mp3 = s->priv_data;
     347             :     AVStream *st;
     348             :     int64_t off;
     349             :     int ret;
     350             :     int i;
     351             : 
     352          23 :     s->metadata = s->internal->id3v2_meta;
     353          23 :     s->internal->id3v2_meta = NULL;
     354             : 
     355          23 :     st = avformat_new_stream(s, NULL);
     356          23 :     if (!st)
     357           0 :         return AVERROR(ENOMEM);
     358             : 
     359          23 :     st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
     360          23 :     st->codecpar->codec_id = AV_CODEC_ID_MP3;
     361          23 :     st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
     362          23 :     st->start_time = 0;
     363             : 
     364             :     // lcm of all mp3 sample rates
     365          23 :     avpriv_set_pts_info(st, 64, 1, 14112000);
     366             : 
     367          23 :     s->pb->maxsize = -1;
     368          23 :     off = avio_tell(s->pb);
     369             : 
     370          23 :     if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
     371          12 :         ff_id3v1_read(s);
     372             : 
     373          23 :     if(s->pb->seekable & AVIO_SEEKABLE_NORMAL)
     374          23 :         mp3->filesize = avio_size(s->pb);
     375             : 
     376          23 :     if (mp3_parse_vbr_tags(s, st, off) < 0)
     377          12 :         avio_seek(s->pb, off, SEEK_SET);
     378             : 
     379          23 :     ret = ff_replaygain_export(st, s->metadata);
     380          23 :     if (ret < 0)
     381           0 :         return ret;
     382             : 
     383          23 :     off = avio_tell(s->pb);
     384        1298 :     for (i = 0; i < 64 * 1024; i++) {
     385             :         uint32_t header, header2;
     386             :         int frame_size;
     387         649 :         if (!(i&1023))
     388          23 :             ffio_ensure_seekback(s->pb, i + 1024 + 4);
     389         649 :         frame_size = check(s->pb, off + i, &header);
     390         649 :         if (frame_size > 0) {
     391          23 :             ret = avio_seek(s->pb, off, SEEK_SET);
     392          23 :             if (ret < 0)
     393           0 :                 return ret;
     394          23 :             ffio_ensure_seekback(s->pb, i + 1024 + frame_size + 4);
     395          23 :             ret = check(s->pb, off + i + frame_size, &header2);
     396          46 :             if (ret >= 0 &&
     397          23 :                 (header & SAME_HEADER_MASK) == (header2 & SAME_HEADER_MASK))
     398             :             {
     399          23 :                 av_log(s, i > 0 ? AV_LOG_INFO : AV_LOG_VERBOSE, "Skipping %d bytes of junk at %"PRId64".\n", i, off);
     400          23 :                 ret = avio_seek(s->pb, off + i, SEEK_SET);
     401          23 :                 if (ret < 0)
     402           0 :                     return ret;
     403          23 :                 break;
     404           0 :             } else if (ret == CHECK_SEEK_FAILED) {
     405           0 :                 av_log(s, AV_LOG_ERROR, "Invalid frame size (%d): Could not seek to %"PRId64".\n", frame_size, off + i + frame_size);
     406           0 :                 return AVERROR(EINVAL);
     407             :             }
     408         626 :         } else if (frame_size == CHECK_SEEK_FAILED) {
     409           0 :             av_log(s, AV_LOG_ERROR, "Failed to read frame size: Could not seek to %"PRId64".\n", (int64_t) (i + 1024 + frame_size + 4));
     410           0 :             return AVERROR(EINVAL);
     411             :         }
     412         626 :         ret = avio_seek(s->pb, off, SEEK_SET);
     413         626 :         if (ret < 0)
     414           0 :             return ret;
     415             :     }
     416             : 
     417             :     // the seek index is relative to the end of the xing vbr headers
     418         123 :     for (i = 0; i < st->nb_index_entries; i++)
     419         100 :         st->index_entries[i].pos += avio_tell(s->pb);
     420             : 
     421             :     /* the parameters will be extracted from the compressed bitstream */
     422          23 :     return 0;
     423             : }
     424             : 
     425             : #define MP3_PACKET_SIZE 1024
     426             : 
     427        2799 : static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
     428             : {
     429        2799 :     MP3DecContext *mp3 = s->priv_data;
     430             :     int ret, size;
     431             :     int64_t pos;
     432             : 
     433        2799 :     size= MP3_PACKET_SIZE;
     434        2799 :     pos = avio_tell(s->pb);
     435        2799 :     if(mp3->filesize > ID3v1_TAG_SIZE && pos < mp3->filesize)
     436        2782 :         size= FFMIN(size, mp3->filesize - pos);
     437             : 
     438        2799 :     ret= av_get_packet(s->pb, pkt, size);
     439        2799 :     if (ret <= 0) {
     440          17 :         if(ret<0)
     441          17 :             return ret;
     442           0 :         return AVERROR_EOF;
     443             :     }
     444             : 
     445        2782 :     pkt->flags &= ~AV_PKT_FLAG_CORRUPT;
     446        2782 :     pkt->stream_index = 0;
     447             : 
     448        2782 :     return ret;
     449             : }
     450             : 
     451             : #define SEEK_WINDOW 4096
     452             : 
     453       17646 : static int check(AVIOContext *pb, int64_t pos, uint32_t *ret_header)
     454             : {
     455       17646 :     int64_t ret = avio_seek(pb, pos, SEEK_SET);
     456             :     uint8_t header_buf[4];
     457             :     unsigned header;
     458             :     MPADecodeHeader sd;
     459       17646 :     if (ret < 0)
     460           0 :         return CHECK_SEEK_FAILED;
     461             : 
     462       17646 :     ret = avio_read(pb, &header_buf[0], 4);
     463             :     /* We should always find four bytes for a valid mpa header. */
     464       17646 :     if (ret < 4)
     465           0 :         return CHECK_SEEK_FAILED;
     466             : 
     467       17646 :     header = AV_RB32(&header_buf[0]);
     468       17646 :     if (ff_mpa_check_header(header) < 0)
     469       17424 :         return CHECK_WRONG_HEADER;
     470         222 :     if (avpriv_mpegaudio_decode_header(&sd, header) == 1)
     471           0 :         return CHECK_WRONG_HEADER;
     472             : 
     473         222 :     if (ret_header)
     474          46 :         *ret_header = header;
     475         222 :     return sd.frame_size;
     476             : }
     477             : 
     478          26 : static int64_t mp3_sync(AVFormatContext *s, int64_t target_pos, int flags)
     479             : {
     480          26 :     int dir = (flags&AVSEEK_FLAG_BACKWARD) ? -1 : 1;
     481             :     int64_t best_pos;
     482             :     int best_score, i, j;
     483             :     int64_t ret;
     484             : 
     485          26 :     avio_seek(s->pb, FFMAX(target_pos - SEEK_WINDOW, 0), SEEK_SET);
     486          26 :     ret = avio_seek(s->pb, target_pos, SEEK_SET);
     487          26 :     if (ret < 0)
     488           0 :         return ret;
     489             : 
     490             : #define MIN_VALID 3
     491          26 :     best_pos = target_pos;
     492          26 :     best_score = 999;
     493       16850 :     for(i=0; i<SEEK_WINDOW; i++) {
     494       16850 :         int64_t pos = target_pos + (dir > 0 ? i - SEEK_WINDOW/4 : -i);
     495       16850 :         int64_t candidate = -1;
     496       16850 :         int score = 999;
     497             : 
     498       16850 :         if (pos < 0)
     499           0 :             continue;
     500             : 
     501       17026 :         for(j=0; j<MIN_VALID; j++) {
     502       16974 :             ret = check(s->pb, pos, NULL);
     503       16974 :             if(ret < 0) {
     504       16798 :                 if (ret == CHECK_WRONG_HEADER) {
     505       16798 :                     break;
     506           0 :                 } else if (ret == CHECK_SEEK_FAILED) {
     507           0 :                     av_log(s, AV_LOG_ERROR, "Could not seek to %"PRId64".\n", pos);
     508           0 :                     return AVERROR(EINVAL);
     509             :                 }
     510             :             }
     511         176 :             if ((target_pos - pos)*dir <= 0 && FFABS(MIN_VALID/2-j) < score) {
     512          69 :                 candidate = pos;
     513          69 :                 score = FFABS(MIN_VALID/2-j);
     514             :             }
     515         176 :             pos += ret;
     516             :         }
     517       16850 :         if (best_score > score && j == MIN_VALID) {
     518          48 :             best_pos = candidate;
     519          48 :             best_score = score;
     520          48 :             if(score == 0)
     521          26 :                 break;
     522             :         }
     523             :     }
     524             : 
     525          26 :     return avio_seek(s->pb, best_pos, SEEK_SET);
     526             : }
     527             : 
     528         128 : static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
     529             :                     int flags)
     530             : {
     531         128 :     MP3DecContext *mp3 = s->priv_data;
     532             :     AVIndexEntry *ie, ie1;
     533         128 :     AVStream *st = s->streams[0];
     534             :     int64_t best_pos;
     535         128 :     int fast_seek = s->flags & AVFMT_FLAG_FAST_SEEK;
     536         128 :     int64_t filesize = mp3->header_filesize;
     537             : 
     538         128 :     if (filesize <= 0) {
     539          48 :         int64_t size = avio_size(s->pb);
     540          48 :         if (size > 0 && size > s->internal->data_offset)
     541          48 :             filesize = size - s->internal->data_offset;
     542             :     }
     543             : 
     544         128 :     if (mp3->xing_toc && (mp3->usetoc || (fast_seek && !mp3->is_cbr))) {
     545           0 :         int64_t ret = av_index_search_timestamp(st, timestamp, flags);
     546             : 
     547             :         // NOTE: The MP3 TOC is not a precise lookup table. Accuracy is worse
     548             :         // for bigger files.
     549           0 :         av_log(s, AV_LOG_WARNING, "Using MP3 TOC to seek; may be imprecise.\n");
     550             : 
     551           0 :         if (ret < 0)
     552           0 :             return ret;
     553             : 
     554           0 :         ie = &st->index_entries[ret];
     555         128 :     } else if (fast_seek && st->duration > 0 && filesize > 0) {
     556          26 :         if (!mp3->is_cbr)
     557           0 :             av_log(s, AV_LOG_WARNING, "Using scaling to seek VBR MP3; may be imprecise.\n");
     558             : 
     559          26 :         ie = &ie1;
     560          26 :         timestamp = av_clip64(timestamp, 0, st->duration);
     561          26 :         ie->timestamp = timestamp;
     562          26 :         ie->pos       = av_rescale(timestamp, filesize, st->duration) + s->internal->data_offset;
     563             :     } else {
     564         102 :         return -1; // generic index code
     565             :     }
     566             : 
     567          26 :     best_pos = mp3_sync(s, ie->pos, flags);
     568          26 :     if (best_pos < 0)
     569           0 :         return best_pos;
     570             : 
     571          26 :     if (mp3->is_cbr && ie == &ie1 && mp3->frames) {
     572          26 :         int frame_duration = av_rescale(st->duration, 1, mp3->frames);
     573          26 :         ie1.timestamp = frame_duration * av_rescale(best_pos - s->internal->data_offset, mp3->frames, mp3->header_filesize);
     574             :     }
     575             : 
     576          26 :     ff_update_cur_dts(s, st, ie->timestamp);
     577          26 :     return 0;
     578             : }
     579             : 
     580             : static const AVOption options[] = {
     581             :     { "usetoc", "use table of contents", offsetof(MP3DecContext, usetoc), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, AV_OPT_FLAG_DECODING_PARAM},
     582             :     { NULL },
     583             : };
     584             : 
     585             : static const AVClass demuxer_class = {
     586             :     .class_name = "mp3",
     587             :     .item_name  = av_default_item_name,
     588             :     .option     = options,
     589             :     .version    = LIBAVUTIL_VERSION_INT,
     590             :     .category   = AV_CLASS_CATEGORY_DEMUXER,
     591             : };
     592             : 
     593             : AVInputFormat ff_mp3_demuxer = {
     594             :     .name           = "mp3",
     595             :     .long_name      = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
     596             :     .read_probe     = mp3_read_probe,
     597             :     .read_header    = mp3_read_header,
     598             :     .read_packet    = mp3_read_packet,
     599             :     .read_seek      = mp3_seek,
     600             :     .priv_data_size = sizeof(MP3DecContext),
     601             :     .flags          = AVFMT_GENERIC_INDEX,
     602             :     .extensions     = "mp2,mp3,m2a,mpa", /* XXX: use probe */
     603             :     .priv_class     = &demuxer_class,
     604             : };

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