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

[Hans J. Koch]

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 ;-)

> 
> > 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.

Thanks,
Hans