[Bug 10693] New: Need a means for navigating between related timed tracks of media elements


           Summary: Need a means for navigating between related timed
                    tracks of media elements
           Product: HTML WG
           Version: unspecified
          Platform: PC
        OS/Version: All
            Status: NEW
          Keywords: a11ytf
          Severity: normal
          Priority: P2
         Component: HTML5 spec (editor: Ian Hickson)
        AssignedTo: ian@hixie.ch
        ReportedBy: silviapfeiffer1@gmail.com
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-wg-issue-tracking@w3.org,

For accessibility purposes, but also for other annotation purposes, timed
tracks for media elements are often not independent, but are provided at
different resolution levels. For example, a recording of a book reading can
have chapters and paragraphs to navigate between. Or a movie can have shots,
scenes and chapters. Or an opera can have scenes and acts. I expect them to be
marked up as separate text tracks. It must thus be possible for accessibility
purposes to switch between these levels easily using a keyboard and this
switching to affect the playback position in the media resource.

For example, I envisage a hierarchical relationship between such timed tracks
and a shortcut key to switch up and down this hierarchy.

I am not sure how this can be implemented best. Maybe it requires extra markers
on the tracks to signify that tracks relate to each other and how - something
like the z-level in CSS.

Also in this context: the usefulness of timed track cues for navigation
purposes cannot be under-estimated. If, for example, we can mark up cues with a
semantic meaning, then we can navigate just between those cues that match a
certain semantic. We could, for example, navigate to all the advertising blocks
in a recording from TV (or alternatively to all the non-advertising blocks).
Even though these cues would all live in the same timed track, navigation
should be enabled for such fine-grained access.

This may well need to be something that is added by browsers to the controls on
a media element, but may also require extra markup - I am not sure yet how to
solve this best.

(More information in this area at:

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Received on Thursday, 23 September 2010 04:49:59 UTC