mov demuxer is broken on fragmented MP4 files with multiple trun boxes per sidx entry

[dbuitenh]

Summary of the bug:

FFmpeg makes the assumption that fragmented MP4 files will have exactly one 'trun' box per entry in the 'sidx' box (see here: ​http://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavformat/mov.c;h=24de5429d1d546473c27e7d7291f477ea3fa79d5;hb=HEAD#l4747). This is not the case and the spec explicitly allows multiple 'trun' boxes (chunks) per sidx entry. Other players, browsers, and demuxers handle this corectly. FFmpeg ends up resetting the PTS and DTS at each new trun box, resulting in repeated timestamps.

Sample with multiple trun per sidx (broken): ​http://chromashift.org/vd.mp4
Sample with single trun per sidx (works): ​http://chromashift.org/vd2.mp4

How to reproduce:

FFmpeg example:

% ffmpeg -i vd.mp4 -f null -
ffmpeg version N-94258-g10f3793823 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 8 (Debian 8.3.0-19)
  configuration: --enable-static --disable-shared
  libavutil      56. 30.100 / 56. 30.100
  libavcodec     58. 53.101 / 58. 53.101
  libavformat    58. 28.101 / 58. 28.101
  libavdevice    58.  7.100 / 58.  7.100
  libavfilter     7. 56.101 /  7. 56.101
  libswscale      5.  4.101 /  5.  4.101
  libswresample   3.  4.100 /  3.  4.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '../chopshop/vd.mp4':
  Metadata:
    major_brand     : dash
    minor_version   : 0
    compatible_brands: dashmp42mp41iso6
    creation_time   : 2019-08-09T15:55:03.000000Z
  Duration: 00:01:58.66, start: 0.000000, bitrate: 301 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, smpte170m), 426x240, 15 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 48k tbc (default)
    Metadata:
      creation_time   : 2019-08-09T15:55:03.000000Z
      handler_name    : L-SMASH Video Handler
      encoder         : AVC Coding
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> wrapped_avframe (native))
Press [q] to stop, [?] for help
Output #0, null, to 'pipe:':
  Metadata:
    major_brand     : dash
    minor_version   : 0
    compatible_brands: dashmp42mp41iso6
    encoder         : Lavf58.28.101
    Stream #0:0(und): Video: wrapped_avframe, yuv420p, 426x240, q=2-31, 200 kb/s, 23.98 fps, 23.98 tbn, 23.98 tbc (default)
    Metadata:
      creation_time   : 2019-08-09T15:55:03.000000Z
      handler_name    : L-SMASH Video Handler
      encoder         : Lavc58.53.101 wrapped_avframe
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x563629252700] DTS -2002 < 9009 out of order

FFprobe example:

% ffprobe -show_packets vd.mp4 | grep 'dts='
dts=-2002
dts=-1001
dts=0
dts=1001
dts=2002
dts=3003
dts=4004
dts=5005
dts=6006
dts=7007
dts=8008
dts=9009
dts=-2002
dts=-1001
dts=0
dts=1001
dts=2002
dts=3003
dts=4004
dts=5005
dts=6006
dts=7007
dts=8008
dts=9009
dts=-2002
dts=-1001
dts=0
dts=1001
dts=2002
dts=3003
dts=4004
dts=5005
dts=6006
dts=7007
dts=8008
dts=9009
dts=-2002
dts=-1001

[... snip ...]

[Carl Eugen Hoyos]

Regression since 4a9d32baca3af0d1831f9556a922c7ab5b426b10, possible duplicate of ticket #7377.

[Jun Zhao]

Can you try this patch: ​https://patchwork.ffmpeg.org/patch/14482/

[Carl Eugen Hoyos]

Fixed by John Stebbins in 9f4054a0cb27503e535804ab8c2b58cc91c72591