[Bug 26921] [InbandTracks] DASH trackId

https://www.w3.org/Bugs/Public/show_bug.cgi?id=26921

Bob Lund <b.lund@cablelabs.com> changed:

           What    |Removed                     |Added
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                 CC|                            |b.lund@cablelabs.com

--- Comment #1 from Bob Lund <b.lund@cablelabs.com> ---
(In reply to Cyril Concolato from comment #0)
> "Content of the 'id' attribute in the AdaptationSet or ContentComponent
> element. Empty string if 'id' attribute is not present."
> 
> The AdaptationSet@id is not unique within an MPD, but within a Period. The
> Period@id is unique within an MPD, even after MPD updates. Similarly, the
> ContentComponent@id is unique only within the AdaptationSet. Additionally,
> it is not clear how representations are exposed.

HTML audio, video and text tracks should correspond to DASH AdaptationSet or
ContentComponent. Different Representations within an AdaptionSet aren't
different HTML tracks.

The DASH spec says this about Representation "By collecting different
Representations in one Adaptation Set, the Media Presentation author expresses
that the Representations represent perceptually equivalent content. Typically
this means, that clients may switch dynamically from Representation to
Representation within an Adaptation Set in order to adapt to network conditions
or other factors."

The DASH spec also requires (section 5.3.3.1) that all Representations in an
AdaptationSet have the same values for attributes that are used to set HTML
track @kind, @language and @label.

The DASH access engine will select segments from different representations; it
isn't a track selection function.

> 
> I'd suggest using the triplets (Period@id, AdaptationSet@id,
> Representation@id (or ContentComponent@id) to generate an id for the track.
> It may be useful to use the MPD fragment identifiers for that but I'm not
> sure we can address representations or sub-representations properly.

Seems like (Period@id, AdaptationSet@id [, ContentComponent@id]).

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Received on Tuesday, 30 September 2014 16:39:49 UTC