[FFmpeg-trac] #7843(undetermined:closed): FFmpeg not outputting to spec MKV files
FFmpeg
trac at avcodec.org
Tue Apr 16 02:51:17 EEST 2019
#7843: FFmpeg not outputting to spec MKV files
-------------------------------------+-------------------------------------
Reporter: | Owner:
alexrichmond |
Type: defect | Status: closed
Priority: normal | Component:
| undetermined
Version: unspecified | Resolution: duplicate
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
Changes (by mkver):
* status: new => closed
* resolution: => duplicate
Comment:
1. As cehoyos has already said, this is not a valid ticket in the current
form.
2. Are you sure your subtitles are plain text and that you are not
accidentally muxing a DVB subtitles stream? Because actually c:s copy
would AFAIK not work if your input were a teletext stream.
3. I think I already know what this is about:
a) FFmpeg writes unknown-length subtitle blocks as BlockGroups with a
duration element indicating a duration of zero. This is insane and I
intend to change this (after my current open patchset for the Matroska
muxer has been dealt with...), but it is not spec-incompliant.
b) mkvalidator's error is based upon an insane and now removed part of the
Matroska specs: That a BlockGroup with a duration of zero can't be a
keyframe. This has since been removed (see https://github.com/Matroska-Org
/matroska-specification/commit/9313a00f7391a285f95e9d6f0a5f8f3f80ed4779),
but mkvalidator 0.5.2 has not been fixed. A PR for this is here:
https://github.com/Matroska-Org/foundation-source/pull/40, but it hasn't
been accepted yet.
4. Did you really use a current version of mkvmerge? Newer versions (since
31.0) keep a BlockGroup with an explicit duration of 0ms that way, so that
mkvalidator's error should also be emitted for the remuxed file; earlier
versions mostly muxed such subtitles as SimpleBlocks. The relevant
mkvmerge issue is 2490: https://gitlab.com/mbunkus/mkvtoolnix/issues/2490
5. Btw: This is also a duplicate of #2023. Therefore closed.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/7843#comment:2>
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