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

Silvia Pfeiffer silviapfeiffer1 at gmail.com
Sat Nov 15 05:58:07 PST 2008

On Sat, Nov 15, 2008 at 12:11 AM, Hans J. Koch <hjk at linutronix.de> wrote:
> On Fri, Nov 14, 2008 at 12:30:25PM +0100, ogg.k.ogg.k at googlemail.com wrote:
>> > Chapters are a list of timepoints stored in the metadata. They are an
>> > information for player software that is usually used to allow the user
>> > to jump to certain significant points within a stream. This probably
>> I don't think anything currently in Ogg can do this. The closest I can
>> think of is CMML's clip concept, but you'd still have to parse the entire
>> stream to find them all.
> That's nearly useless for DVD-like applications.
>> One could build an index of them to place them in a Skeleton message
>> header though, but there is nothing to do that AFAIK.
> I guess this is not neccessary. A simple chunk of metadata containing
> the list of times at the beginning of a file would suffice. OGM simply
> uses text stored in comment fields for that. I wouldn't recommend
> comments for a general approach, but whatever format we choose, it
> should probably not be too difficult to specify and implement it.
> Looking at some of the accessibility pages Silvia mentioned, I think
> that ogg specs are very much focused on web video. I'll follow that
> discussion and will remind ogg developers from time to time that there
> are still one or two people who watch videos from good old files on
> their disk ;-)

Not kate, no. Kate was definitely defined for offline work.

>> > Chapters like this are mainly used on video DVDs, but are also defined for
>> > SVCD and OGM containers. My personal use is watching movies from SDcard
>> > or harddisk. I'm the type of guy who often wants to watch only some
>> > parts of a movie, and chapters greatly simplify finding a certain scene
>> > (or skip one that is too exciting...).
>> If you are transcoding a DVD, you might want to look at the diffs directory
>> in libkate, there is a patch to Thoggen (Linux based DVD transcoder) that
>> automatically converts DVD subtitles to Kate streams, though it also requires
>> a set of patches to GStreamer (also found in the same directory) to be applied.
> Well, I gave up using graphical DVD rippers years ago since none of them
> does what I want. Meanwhile I got used to create my audio, video,
> subtitle, and chapter data using various commandline tools. The best
> solution for me would probably be oggzmerge understanding srt files and
> some textfile containing my chapter points.

We might be rather close to the specifications for that. Tool support
is a different question, as usual.


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