[Bug 24997] Add "Return values for Text.kind" table

https://www.w3.org/Bugs/Public/show_bug.cgi?id=24997

--- Comment #10 from Bob Lund <b.lund@cablelabs.com> ---
(In reply to Bob Lund from comment #7)
> (In reply to Bob Lund from comment #6)
> > (In reply to Silvia Pfeiffer from comment #5)
> > > I have prepared a patch for this in a branch at
> > > https://github.com/w3c/html/commit/f91c1932220ab4272d2b2b4e6c9f3679251fefa1 .
> > > 
> > > Could you please check that this is all correct, in particular for MPEG-2,
> > > MPEG-4 and DASH (I checked Ogg and WebM and am quite confident on those).
> > 
> > For MPEG-4 metadata text track, you've used a list of sample entry codes
> > instead of 'meta' handler type. Beyond, 'mett' and 'metx', I do not know if
> > this list is accurate or not.
> > 
> > The table for setting text track kind, label and language looks good. 
> 
> While the phrase "contain private sections ("payload_unit_start_indicator"
> == 1)" for identifying an MPEG-2 TS metadata text track is technically
> correct, it requires the UA to wait for private section before creating the
> text track.
> 
> It might be more simple for the UA to create a metadata text track for
> MPEG-2 TS stream_type 0x05, 0x80 - 0xff without waiting for a private
> section indicated by a payload_unit_start_indicator == 1. If none are ever
> received, no private section cues would ever be created.

I think the UA should create the metadata text track for these stream_types and
NOT wait for packets to determine the payload_unit_start_indicator; script will
know what to expect.

So, the specific change is at line 33161 in
https://github.com/w3c/html/commit/f91c1932220ab4272d2b2b4e6c9f3679251fefa1.
Drop the text "contain private sections ("payload_unit_start_indicator" == 1)"

> 
> > 
> > > 
> > > Further:
> > > 
> > > * In bug 25044 you're requesting some similar specifications for setting the
> > > id, label and language on AudioTrack and VideoTrack. Is that identical to
> > > the TextTrack settings for these attributes?
> > 
> > Yes, the rules for setting id, label and language should apply to audio and
> > video as well as text tracks.
> > 
> > > 
> > > * Please particularly check the @kind settings for MPEG-2, MPEG-4 and DASH.
> > > MPEG-2 and MPEG-4 sound particularly restrictive, e.g. there is no fallback
> > > to @kind=metadata.
> > 
> > For MPEG-2 TS there are many many non-audio/video stream types beyond those
> > explicitly identified as metadata (0x05, 0x80 - 0xff), with no identified
> > use case for exposing them to script.
> > 
> > For MPEG-4, it seems that all metadata tracks would be identified by a
> > handler type of 'meta'. Is there a use case where that is not so?

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Received on Tuesday, 18 March 2014 14:55:27 UTC