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[Bug 13359] <track> A way is needed to identify the type of data in a track element

From: <bugzilla@jessica.w3.org>
Date: Mon, 12 Dec 2011 16:07:25 +0000
To: public-html-a11y@w3.org
Message-Id: <E1Ra8PV-0005DR-5i@jessica.w3.org>

--- Comment #30 from Bob Lund <b.lund@cablelabs.com> 2011-12-12 16:07:18 UTC ---

(In reply to comment #29)
> (In reply to comment #27)
> >
> > Ogg[1] - Ogg skeleton header fields: content_type, role, name
> content_type == MIME type in Ogg; is that really what you're after?

If the script needs MIME type to identify the format of a metadata track, then

> role is already mapped to the @role attribute; what more do you expect from it?

I don't see a role attribute in either the HTMLTrackElement of TextTrack

> name is already mapped to the @kind attribute; what more do you expect from it?

Definition of @kind enumerates a set of kinds. There is only a single metadata
kind. The definition of name in http://wiki.xiph.org/SkeletonHeaders#Name
states it is a free text string. Inclusion of name could be used to
discriminate the specific type of metadata.

> > MPEG-2 TS[2] - Program map table entry fields: stream_type, any descriptors
> > 
> > DASH[3] - MPD Role element, e.g.  <Role schemeIdUri=
> Looks lie your post got cut off.
> You've missed WebM.

Thanks - WebM, MPEG-4 and DASH got cut off. Here is the complete list again.

Ogg - Ogg skeleton header fields: content_type, role, name [1]

MPEG-2 TS - Program map table entry fields: stream_type field in the PMT, any
descriptors [2]

DASH - MPD Role element, e.g.  <Role schemeIdUri=”urn:mpeg:DASH:role:2011”
value=”subtitle”/> [3]. NOTE: DASH has defined a scheme with a set of values.
It is expected that other organizations will define additional schemes as

WebM - TrackType and CodecID [4].

ISOBMFF (MPEG-4) - Contents of the handler reference box (hdlr) in each track :
attributes handler_type and name [5]. NOTE: MPEG only defines three types of
track handlers: video, audio and hint. Other organizations can extend the MPEG
handler reference box to define new types of tracks.

[1] http://wiki.xiph.org/SkeletonHeaders
[2] ITU H.222.0 (5/2006) Table 2-33
[4] http://matroska.org/technical/specs/index.html
[5] ISO/IEC 14496-12


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Received on Monday, 12 December 2011 16:07:31 UTC

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