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

Hans J. Koch hjk at linutronix.de
Fri Nov 14 03:27:23 PST 2008

On Fri, Nov 14, 2008 at 10:59:43AM +1100, Silvia Pfeiffer wrote:
> Hi Hans,

Hi Silvia,

> 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.

Neither am I. I'll try. For OGM containers, xine has the best support
for both chapters and subtitles. MPlayer does subtitles, but no
chapters, at least in the version I use. Same applies to VLC.

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

I don't care much about the format. Yes, ATM it's srt, but as long as
it's a text format, it's easy enough for me to convert it to something
different. It should really be a text format, I don't want to need a
tool other than vim to edit my subtitles ;-)

> 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.

OK, thanks!

> 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.

Looks interesting...

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

Thanks a lot!


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