[Bug 13358] New: An event is needed that signals a change in the track composition of a media resource.


           Summary: An event is needed that signals a change in the track
                    composition of a media resource.
           Product: HTML WG
           Version: unspecified
          Platform: PC
        OS/Version: Windows XP
            Status: NEW
          Severity: normal
          Priority: P2
         Component: HTML5 spec (editor: Ian Hickson)
        AssignedTo: ian@hixie.ch
        ReportedBy: b.lund@cablelabs.com
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-wg-issue-tracking@w3.org,

Problem statement:

Some types of media resources that will be processed by Web browsers will have
a set of tracks where tracks may be deleted or new tracks added over the play
time of the media resource. These tracks may be video, audio and text tracks.
Use cases identified have been HTTP Live Streams and MPEG-2 transport streams
used for cable television scheduled channels [1].

The current HTML5 specification references support for live streams [2][3][4].
An event is needed to signal when there is a change to the set of tracks in the
media resource for a live stream given the use cases identified above.

Possible solution:

Define a new event, e.g. “metadatachanged”, that indicates a track has been
added or removed from the media resource.

Specification sections affected:

“HTML5 A vocabulary and associated APIs for HTML and XHTML” sections:

Add onmetadatachanged in all sections where there is onloadedmetadata:
“Documents in the DOM”, “Global attributes”, “Mediacontrollers”, “The window
object”, “Event handlers”, “Attributes”

Define metadatachanged event in section “Loading the media resource”.

Add metadatachanged in section “Event summary”

[1] http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2011-June/031972.html
[2] Offsets into the media resource, "If the media resource is not
known to be bounded (e.g. streaming radio, or a live event with no announced
end time)"
[3] Media controllers, "... when playing back a live stream..."
[4] Best practices for implementors of media elements, "...if the
user is watching a live stream..."

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Received on Monday, 25 July 2011 22:01:16 UTC