FFmpeg moves content of first chapter from a mkv file into global

[Fabian]

Summary of the bug:

When I create a mkv file with chapters using the ffmetadata file and then parse it by ffmpeg again, it will remove the first chapter and some metadata of it become global.

How to reproduce:

% ./ffmpeg -i src_meta.txt -i src_video.webm -c copy tgt_video.mkv
ffmpeg version N-54769-g5ceffb1 Copyright (c) 2000-2013 the FFmpeg developers
  built on Jul 16 2013 22:14:51 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
  configuration: --disable-yasm
  libavutil      52. 39.100 / 52. 39.100
  libavcodec     55. 18.102 / 55. 18.102
  libavformat    55. 12.102 / 55. 12.102
  libavdevice    55.  3.100 / 55.  3.100
  libavfilter     3. 81.101 /  3. 81.101
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
Input #0, ffmetadata, from 'src_meta.txt':
  Duration: 00:00:09.42, start: 0.000000, bitrate: 0 kb/s
    Chapter #0.0: start 0.000000, end 0.990000
    Metadata:
      TITLE           : Chapter 1
      TYPE            : c1
    Chapter #0.1: start 1.000000, end 9.420000
    Metadata:
      TITLE           : Chapter 2
      TYPE            : c2
Input #1, matroska,webm, from 'src_video.webm':
  Duration: 00:00:09.42, start: 0.000000, bitrate: 1827 kb/s
    Stream #1:0: Video: vp8, yuv420p, 1280x720, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 1k tbn, 1k tbc (default)
    Stream #1:1: Audio: vorbis, 48000 Hz, stereo, fltp (default)
Output #0, matroska, to 'tgt_video.mkv':
  Metadata:
    encoder         : Lavf55.12.102
    Chapter #0.0: start 0.000000, end 0.990000
    Metadata:
      TITLE           : Chapter 1
      TYPE            : c1
    Chapter #0.1: start 1.000000, end 9.420000
    Metadata:
      TITLE           : Chapter 2
      TYPE            : c2
    Stream #0:0: Video: vp8 (VP80 / 0x30385056), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 25 fps, 1k tbn, 1k tbc (default)
    Stream #0:1: Audio: vorbis (oV[0][0] / 0x566F), 48000 Hz, stereo (default)
Stream mapping:
  Stream #1:0 -> #0:0 (copy)
  Stream #1:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=  234 fps=0.0 q=-1.0 Lsize=    2101kB time=00:00:09.39 bitrate=1831.7kbits/s    
video:1945kB audio:146kB subtitle:0 global headers:0kB muxing overhead 0.467363%

% ./ffmpeg -i tgt_video.mkv -f ffmetadata tgt_meta.txt
ffmpeg version N-54769-g5ceffb1 Copyright (c) 2000-2013 the FFmpeg developers
  built on Jul 16 2013 22:14:51 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
  configuration: --disable-yasm
  libavutil      52. 39.100 / 52. 39.100
  libavcodec     55. 18.102 / 55. 18.102
  libavformat    55. 12.102 / 55. 12.102
  libavdevice    55.  3.100 / 55.  3.100
  libavfilter     3. 81.101 /  3. 81.101
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
Input #0, matroska,webm, from 'tgt_video.mkv':
  Metadata:
    ENCODER         : Lavf55.12.102
    TYPE            : c1
  Duration: 00:00:09.42, start: 0.000000, bitrate: 1827 kb/s
    Chapter #0.0: start 1.000000, end 9.420000
    Metadata:
      title           : Chapter 2
      TYPE            : c2
    Stream #0:0: Video: vp8, yuv420p, 1280x720, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 1k tbn, 1k tbc (default)
    Stream #0:1: Audio: vorbis, 48000 Hz, stereo, fltp (default)
Output #0, ffmetadata, to 'tgt_meta.txt':
  Metadata:
    ENCODER         : Lavf55.12.102
    TYPE            : c1
    Chapter #0.0: start 1.000000, end 9.420000
    Metadata:
      title           : Chapter 2
      TYPE            : c2
Stream mapping:
Press [q] to stop, [?] for help
size=       0kB time=-577014:-32:-22.-77 bitrate=N/A    
video:0kB audio:0kB subtitle:0 global headers:0kB muxing overhead inf%
Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)

As you can see, the first chapter is missing and starts directly with the second. Additionally it shows the TYPE metadata of the first chapter in the global metadata.

I used mkvtoolnix to look into the file and there the first chapter exists, so it looks like the decoding failed. Although I tried it with another proprietary mkv file and there it works fine. Unfortunately I can't upload that file.

I used ​http://http://commons.wikimedia.org/wiki/File:Chinese_Signal.webm to encode and this is the metadata file:

;FFMETADATA1
[CHAPTER]
TIMEBASE=1/100
START=0
END=99
TITLE=Chapter 1
TYPE=c1
[CHAPTER]
TIMEBASE=1/100
START=100
END=942
TITLE=Chapter 2
TYPE=c2

And mkvtoolnix is producing the following:

+ EBML head
|+ EBML version: 1
|+ EBML read version: 1
|+ EBML maximum ID length: 4
|+ EBML maximum size length: 8
|+ Doc type: matroska
|+ Doc type version: 2
|+ Doc type read version: 2
+ Segment, size 2151327
|+ Seek head (subentries will be skipped)
|+ EbmlVoid (size: 133)
|+ Segment information
| + Timecode scale: 1000000
| + Muxing application: Lavf55.12.102
| + Writing application: Lavf55.12.102
| + Segment UID:0xf2 0x8c 0x0b 0x70 0x15 0x18 0x4d 0x25 0x54 0xc7 0xfd 0xd7 0x92 0x17 0xe7 0x31 
| + Duration: 9.417s (00:00:09.417)
|+ Segment tracks
| + A track
|  + Track number: 1
|  + Track UID: 1
|  + Lacing flag: 0
|  + Language: und
|  + Default flag: 1
|  + Codec ID: V_VP8
|  + Track type: video
|  + Default duration: 40.000ms (25.000 fps for a video track)
|  + Video track
|   + Pixel width: 1280
|   + Pixel height: 720
|   + Display width: 1280
|   + Display height: 720
| + A track
|  + Track number: 2
|  + Track UID: 2
|  + Lacing flag: 0
|  + Language: und
|  + Default flag: 1
|  + Codec ID: A_VORBIS
|  + Track type: audio
|  + Audio track
|   + Channels: 2
|   + Sampling frequency: 48000
|   + Bit depth: 32
|  + CodecPrivate, length 4256
|+ Chapters
| + EditionEntry
|  + EditionFlagDefault: 1
|  + EditionFlagHidden: 0
|  + ChapterAtom
|   + ChapterUID: 0
|   + ChapterTimeStart: 00:00:00.000000000
|   + ChapterTimeEnd: 00:00:00.990000000
|   + ChapterFlagHidden: 0
|   + ChapterFlagEnabled: 1
|   + ChapterDisplay
|    + ChapterString: Chapter 1
|    + ChapterLanguage: und
|  + ChapterAtom
|   + ChapterUID: 1
|   + ChapterTimeStart: 00:00:01.000000000
|   + ChapterTimeEnd: 00:00:09.420000000
|   + ChapterFlagHidden: 0
|   + ChapterFlagEnabled: 1
|   + ChapterDisplay
|    + ChapterString: Chapter 2
|    + ChapterLanguage: und
|+ Tags
| + Tag
|  + Targets
|  + Simple
|   + Name: ENCODER
|   + String: Lavf55.12.102
| + Tag
|  + Targets
|   + ChapterUID: 0
|  + Simple
|   + Name: TYPE
|   + String: c1
| + Tag
|  + Targets
|   + ChapterUID: 1
|  + Simple
|   + Name: TYPE
|   + String: c2
|+ Cluster

Thanks in advance.

Fabian

[Fabian]

My source metadata

[Fabian]

The result of applying the source metadata to the video on the commons

[Fabian]

The mkvtoolnix's output of the tgt_video.mkv

[jamal]

"ChapterUID: 0"
That seems to the problem. The Matroska demuxer is ignoring the chapter with uid 0, and reading the second one (With uid 1) as if it were the first.

The ffmetadata demuxer assigns the id 0 to the first chapter it reads from src_meta.txt, and the Matroska muxer used it.

mkvalidator doesn't complain about the resulting file tgt_video.mkv, so 0 is a valid value for ChapterUID.

[Carl Eugen Hoyos]

Replying to jamal:

0 is a valid value for ChapterUID.

I don't think this is correct, see ​http://matroska.org/technical/specs/index.html

[jamal]

Replying to cehoyos:

Replying to jamal:

0 is a valid value for ChapterUID.

I don't think this is correct, see ​http://matroska.org/technical/specs/index.html

Odd, I'd expect their own validator to catch that.

[Fabian]

So avformat “simply” needs to start the ChapterUID with 1 instead of 0? That may explain why my proprietary file is working when the ChapterUIDs look like random generated.

Now I have a bunch of mkvs with the wrong ChapterUID, so maybe ffmpeg can support a ChapterUID of 0 and I can simply reformat them to a valid format.

[Carl Eugen Hoyos]

Apparently fixed in 353f302.