[Bug 25353] [DataCue] change DOMString? text to any? value

https://www.w3.org/Bugs/Public/show_bug.cgi?id=25353

--- Comment #3 from Bob Lund <b.lund@cablelabs.com> ---
(In reply to Aaron Colwell from comment #2)
> I'm concerned this will lead to unspeced "protocols" between the UA and the
> web application if we do this. Why is having a generic DataCue that returns
> an any better than defining specific cue types for different types of
> information that can be returned?

There are many types of metadata used in various media containers and,
initially, no way for script to determine what type of metadata was in the
track. I filed a bug [1] to address this limitation. The resolution was
creation of inBandTrackMetadataDispatchType that applied only to metadata text
tracks. This resolution defined what the UA needed to provide so that the UA
could provide script information to decode the track while not requiring the UA
to know the syntax of all the various types of metadata.

As I understand this bug, there may be UAs that can recognize some types of
metadata and, in this case, format the data for script. This ability doesn't
solve the general case I identified in [1]; there are many more types of
metadata that any UA will recognize. Case in point is Nielsen ratings added a
new private data track to MPEG-2 TS and supplied a Web app that used this data
to do ratings on browser based platforms. All the UA needed to do was to
populate the inBand...DispatchType attribute and make the raw cue available.
The UA did not need to be extended to recognize the new metadata cue syntax.

> 
> This feels a little like the postMessage()/onmessage pairing, but the
> posting entity is not actually visible to the web application so it has no
> idea what the universe of things to expect could contain.
> 
> I also feels like this is taking us away from the text track concept into
> something more "timed event"-like which makes me wonder if this should even
> be considered a text track.

I don't see this. The bug is asking for a way so that the UA can format the
metadata for those types it recognizes. The timed aspect of text tracks is
still there.



[1] https://www.w3.org/Bugs/Public/show_bug.cgi?id=13359

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Received on Wednesday, 16 April 2014 16:46:04 UTC