[whatwg] TimedTracks and MPEG transport streams - tracks can change dynamically

Eric Winkelman E.Winkelman at cablelabs.com
Wed Nov 24 08:11:02 PST 2010

I'm investigating how TimedTracks can be used for in-band-data-tracks within MPEG transport streams (used for cable television).

In this format, the number and types of in-band-data-tracks can change over time.  So, for example, when the programming switches from a football game to a movie, an alternate language track may appear that wasn't there before.  Later, when the programming changes again, that language track may be removed.

It's not clear to me how these changes are exposed by the proposed Media Element events.

The "loadedmetadata" event is used to indicate that the TimedTracks are ready, but it appears that it is only fired before playback begins.  Is this event fired again whenever a new track is discovered?  Is there another event that is intended for this situation?

Similarly, is there an event that indicates when a track has been removed?  Or is this also handled by the "loadedmetadata" event somehow?


Eric Winkelman
e.winkelman  cablelabs.com
Cable Television Laboratories, Inc.
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