[whatwg] Proposal for @label attribute associated with kind=metadata TimedTextTracks

Silvia Pfeiffer silviapfeiffer1 at gmail.com
Fri Mar 18 20:22:52 PDT 2011

On Sat, Mar 19, 2011 at 6:29 AM, Eric Winkelman
<E.Winkelman at cablelabs.com> wrote:
> Use Case:
> Many video streams contain in-band metadata for application signaling, and other uses.  By using this metadata, a web page can synchronize an application with the delivered video, or provide other synchronized services.
> An example of this type of metadata is EISS ( http://www.cablelabs.com/specifications/OC-SP-ETV-AM1.0-I06-110128.pdf ) which is used to control applications that are synchronized with a television broadcast.
> In general, a media stream can be expected to carry several types of metadata and the types of metadata may vary in time.
> Problem:
> For in-band metadata tracks, there is neither a standard way to represent the type of metadata in the HTMLTrackElement interface nor is there a standard way to represent multiple different types of metadata tracks.
> Proposal:
> For TimedTextTracks with kind=metadata the @label attribute should contain a MIME type for the metadata and that a track only contain Cues created from metadata of that MIME type.
> This implies that streams with multiple types of metadata require the creation of multiple metadata track objects, one for each MIME type.

I don't understand. Are you saying that right now all tracks that are
of kind=metadata are made available through a single TextTrack? Cause
I don't think that's the case.

Or are you worried about text track files that contain more than one
type of metadata? If the latter, then how is the browser to know how
to separate out the individual cues from a single track into

Can you clarify?


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