[Bug 13357] Additional AudioTrack.kind categories are needed to identify tracks where audio descriptions are premixed with main dialogue.

http://www.w3.org/Bugs/Public/show_bug.cgi?id=13357

--- Comment #4 from Bob Lund <b.lund@cablelabs.com> 2011-08-25 20:21:03 UTC ---
(In reply to comment #3)
> (In reply to comment #2)
> > How is this kind distinguished in existing video formats?
> > 
> > That is, what types would this map to in H.264, WebM, or Ogg files?
> 
> In Ogg such a track would just be under the role "main" because such mixed
> content is not the best way to publish content - it's better to keep such
> content separate. Once mixed, it's basically impossible to get back to the
> individual parts and e.g. remove the audio description again. As such it is the
> new "main". It has also not been a common case to deal with yet.
> 
> This doesn't quite match with the user experience though and where such content
> is delivered, it has to be made clear to the user that the main content has
> such other information in it. In the past I have seen it even mentioned in the
> title displayed above the video and explicitly described in the description to
> point out to the user what they have to expect from the content.
> 
> In a situation where a program has to pick an adequate piece of content, e.g.
> content that actually has an audio description, just using kind=main is indeed
> insufficient. I'm prepared to suggest to Ogg to add the use of "+" to the roles
> attribute to enable use cases such as role="audio/main+audio/audiodesc" or
> role="video/main+video/sign".

In DASH, which is still a work in progress, it appears <role> will be used to
identify if a track is alternate or supplementary. Another <role> in the same
audio set, can identify main or translation.

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Received on Thursday, 25 August 2011 20:21:10 UTC