[Bug 21851] revert removal of text and getCueAsHTML members; address constructor changes

https://www.w3.org/Bugs/Public/show_bug.cgi?id=21851

--- Comment #11 from Silvia Pfeiffer <silviapfeiffer1@gmail.com> ---
(In reply to comment #10)
> If you know what kind of cue it is, then you just use its API.
> 
> If you don't know what kind of cue it is, then the suggested features here
> are pointless.

There is a difference between what the UA knows about the cue and what the JS
dev knows and can do about the cue.

It is possible to have an implementation in a UA that parses timed tracks and
exposes cues, but the UA has no implementation for how to further parse the cue
content. The CableLabs spec at
http://www.cablelabs.com/specifications/CL-SP-HTML5-MAP-I02-120510.pdf talks
about this: to expose the cue as a UTF-16 string, or if it's binary as Base64,
but it does not require an algorithm for what to do with the cue content
thereafter in the UA. Though the UA may be able to provide a hint as to what
the cues are, which it would provide in the
text-track-in-band-metadata-track-dispatch-type (e.g. text/ttml or text/scc).

It would, of course, be better to have a dedicated API for TTMLCue or
SCC708Cue, but if there is no further data than just the cue content,
TextTrackCue is entirely sufficient if it has a .content (or .text) API.

The expectation is then that JS knows what to do with such cues, which I guess
implies that such cues can only work for @kind=metadata tracks.



> > I thought that's what the in-band metadata track dispatch type
> > (http://www.whatwg.org/specs/web-apps/current-work/#text-track-in-band-
> > metadata-track-dispatch-type) was for (see IDL attribute of TextTrack
> > http://www.whatwg.org/specs/web-apps/current-work/#texttrack ).
> 
> That's about different kinds of cues within a specific format (e.g. a
> metadata cue vs a chapter cue in WebVTT). This bug is about different
> formats (e.g. MPEG vs WebVTT).

It's really about both, since the getCueAsHTML() function only makes sense for
cue formats that the UA can render, even when it is already able to parse the
cue file.

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Received on Tuesday, 7 May 2013 22:24:35 UTC