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

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

--- Comment #7 from Bob Lund <b.lund@cablelabs.com> ---
(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.

> 
> > 
> > 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 Monday, 17 March 2014 22:40:54 UTC