[FFmpeg-trac] #8234(avformat:new): mp4 file with id3v2 tag detected as mp4 but still fails decoding

[FFmpeg]

#8234: mp4 file with id3v2 tag detected as mp4 but still fails decoding
-------------------------------------+-------------------------------------
             Reporter:  Mattias      |                    Owner:  (none)
  Wadman                             |
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  avformat
              Version:  git-master   |               Resolution:
             Keywords:  mov aac      |               Blocked By:
  id3v2                              |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Comment (by Mattias Wadman):

 Problem seems to be that the mov demuxer does not correctly compensate for
 tags when when calculating the sample offset. With this patch it works:

 {{{
 diff --git a/libavformat/isom.h b/libavformat/isom.h
 index 64fb7065d5..2c45e50ed0 100644
 --- a/libavformat/isom.h
 +++ b/libavformat/isom.h
 @@ -326,6 +326,7 @@ typedef struct MOVContext {
          int64_t extent_offset;
      } *avif_info;
      int avif_info_size;
 +    int64_t header_offset;
  } MOVContext;

  int ff_mp4_read_descr_len(AVIOContext *pb);
 diff --git a/libavformat/mov.c b/libavformat/mov.c
 index 29bd3103e3..50a8e3308b 100644
 --- a/libavformat/mov.c
 +++ b/libavformat/mov.c
 @@ -4140,7 +4140,7 @@ static void mov_build_index(MOVContext *mov,
 AVStream *st)

          for (i = 0; i < sc->chunk_count; i++) {
              int64_t next_offset = i+1 < sc->chunk_count ?
 sc->chunk_offsets[i+1] : INT64_MAX;
 -            current_offset = sc->chunk_offsets[i];
 +            current_offset = mov->header_offset + sc->chunk_offsets[i];
              while (mov_stsc_index_valid(stsc_index, sc->stsc_count) &&
                  i + 1 == sc->stsc_data[stsc_index + 1].first)
                  stsc_index++;
 @@ -8416,6 +8416,7 @@ static int mov_read_header(AVFormatContext *s)
          return AVERROR(EINVAL);
      }

 +    mov->header_offset = avio_tell(pb);
      mov->fc = s;
      mov->trak_index = -1;
      /* .mov and .mp4 aren't streamable anyway (only progressive download
 if moov is before mdat) */
 }}}
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/8234#comment:4>
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