[ogg-dev] [theora-dev] handling multitrack Ogg

Benjamin M. Schwartz bmschwar at fas.harvard.edu
Tue Feb 2 14:15:47 PST 2010

Silvia Pfeiffer wrote:
> > QuickTime doesn't force a player to use this information. But it needs
> > to be present, otherwise the player has no idea which information goes
> > on top of which other information, e.g. the caption track goes on top
> > of the video. Of course, the player is free to not do any overlaying
> > and draw separate display areas etc.

The player should know that the caption track goes on top of the video
because the caption track is labeled "caption" and the video is labeled
"main", or whatever the agreed-upon labels are for track types.

> > The issue is that this kind of information is not currently available
> > for Ogg tracks, so we need to add it to skeleton.

I agree.  I'm just suggesting that the skeleton content should be
semantic, as much as possible, rather than prescriptive.

> > Nobody wants to refer to such long numbers. They are also really hard
> > to "loop through". But I'll see what we come up with.

They're not numbers; they're strings.  They're opaque identifiers.
Programmers use opaque identifiers all the time.  As for looping through
them, you can do

for (var t in video.tracks) {
	if (video.tracks[t].role == "caption") video.tracks[t].enabled = true;
	if (video.tracks[t].lang == "fr")          video.tracks[t].enabled = true;

To me, that seems even easier than the equivalent int-array for loop.


P.S. Oops, originally replied off-list.

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