[ogg-dev] video chapters and subtitles in ogg containers

Silvia Pfeiffer silviapfeiffer1 at gmail.com
Thu Nov 13 15:59:43 PST 2008

Hi Hans,

At the moment, Ogg supports two text codecs, CMML and Kate. Both of
them are theoretically capable of doing what you want with chapters
and subtitles. The biggest problem is player support.

There is CMML and kate support in vlc, and kate in mplayer though I am
not sure how it is displayed on-screen. Subtitles may display, but
chapter markers, I am not so sure about.

I assume the subtitles that you have are in srt format which is why
you chose ogm as the container format?

You will need to transcode them to CMML or Kate to encode into Ogg.
There is an old python script for cmml at
http://svn.annodex.net/scripts/trunk/subtitles/script-subrip2cmml.py .
I'm not sure something like this exists for kate.
But it should not be too hard to write one.

One more piece of news: I am currently doing a contract for Mozilla
about video accessibility for Ogg. There is a lot of work going on in
this space right now and we expect to have subtitle support by next
year in Firefox with Ogg, but this is currently not the case. The work
is being done on  "accessibility at xiph.org" <accessibility at xiph.org>
and https://wiki.mozilla.org/Accessibility/Video_Accessibility in case
you are interested.

In view of this work, I am considering abandoning CMML and putting it
into a greater framework that is also Web focused. It may have some
similarity to kate, but it will have a stronger Web focus than kate,
which has everything within the file. Then again, I am not sure if I
may just recommend the use of kate to Mozilla. There is some more work

Anyway - I thought I should give you the full picture. :)


On Fri, Nov 14, 2008 at 6:41 AM, Hans J. Koch <hjk at linutronix.de> wrote:
> I'm trying to create files that contain a video stream, one or more
> audio streams, subtitles, and DVD-like chapter information.
> ATM, I use ogm containers that can handle all this. But although ogm
> is supported e.g. by xine (including chapters), it seems to be an
> unofficial hack. Is that correct?
> I'd like to move to ogg containers, since ogm doesn't support theora
> videos. My final goal is one file containing theora video streams,
> vorbis audio streams, chapters, and subtitles
> Looking into the ogg docs, I found capabilities to handle multiple video
> and audio streams in ogg skeleton. But what about meta-data like subtitles
> (in text format, of course) or chapters? I couldn't find anything about this.
> Question: Is this planned for the future?
> Question: Or is it possible and I just didn't see it?
> If yes, how could I help (I'm a programmer) ?
> Thanks,
> Hans
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> ogg-dev mailing list
> ogg-dev at xiph.org
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