[FFmpeg-trac] #5434(undetermined:new): add support of WebVTT subtitles in Matroksa files
FFmpeg
trac at avcodec.org
Wed Apr 13 15:07:36 CEST 2016
#5434: add support of WebVTT subtitles in Matroksa files
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Reporter: Klaus1189 | Type:
Status: new | enhancement
Component: | Priority: normal
undetermined | Version:
Keywords: | unspecified
Blocking: | Blocked By:
Analyzed by developer: 0 | Reproduced by developer: 0
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I contacted Moritz Bunkus, the developer of MKVToolNix, because according
to ironic_monkey from Kodi forum FFMPEG doesn't support the new spec. Here
you can see the full thread at Kodi forum:
http://forum.kodi.tv/showthread.php?tid=261529&pid=2309291
Moritz Bunkus explained the issue to me.
Up until a couple of days ago the storage of WebVTT in Matroska hadn't
been specified yet. What ffmpeg seems to support (D_WEBVTT/…) is an old
and outdated work-in-progress paper by the WebM project[1]. We (as in the
Matroska project) have decided not to use their proposal in Matroska
for several reasons:
1. The proposal is old (from February 2012). The WebVTT specs have changed
considerably since then, and therefore the WebM proposal doesn't handle
several of those additions and changes.
2. It suggests splitting the single WebVTT file into multiple tracks
inside WebM. This is possible but it makes handling of multiple tracks
more difficult than it has to be for demuxers and remuxers. Additionally
there's no way to specify that several tracks belong to the same logical
track and must be handled all at once.
3. The WebM proposal is still a work in progress and WebM still officially
doesn't support subtitles at all[2].
The Matroska project has now formalized the storage of WebVTT in
Matroska[3]. The specs have been added to the Matroska web site[4].
The next step should be to add support in ffmpeg for the current storage
method.
[1] http://wiki.webmproject.org/webm-metadata/temporal-metadata/webvtt-
in-webm
[2] http://www.webmproject.org/docs/container/
[3] http://thread.gmane.org/gmane.comp.multimedia.matroska.devel/5210
[4] https://www.matroska.org/technical/specs/subtitles/webvtt.html
Here you can get a sample file:
https://drive.google.com/file/d/0B4y5u0gBKYqbSFczT1VPc2l5SXM/view?usp=sharing
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Ticket URL: <https://trac.ffmpeg.org/ticket/5434>
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