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Re: [media] Moving forward with captions / subtitles

From: David Singer <singer@apple.com>
Date: Fri, 19 Feb 2010 10:45:50 -0800
Cc: John Foliot <jfoliot@stanford.edu>, philipj@opera.com, Eric Carlson <eric.carlson@apple.com>, Geoff Freed <geoff_freed@wgbh.org>, HTML Accessibility Task Force <public-html-a11y@w3.org>
Message-Id: <A9973B4E-1FAE-4B06-8D3D-237F6EC7C803@apple.com>
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>

On Feb 18, 2010, at 19:13 , Silvia Pfeiffer wrote:
> I am not sure there if MP4 allows to set a track as enabled (or
> provides such a hint to the media players).

Yes, the track enable bit, and also track alternates (really alternatives) are both in MP4.  I think this is a natural way to bundle media -- put the optional features in tracks that get enabled on demand.  My current naive thinking is that a media query might again help here.

On Feb 18, 2010, at 21:56 , Silvia Pfeiffer wrote:

> On Fri, Feb 19, 2010 at 4:49 PM, Eric Carlson <eric.carlson@apple.com> wrote:
>>  I am in favor of using the same model we have with <source> - the content author "describes" each alternate with attributes and the UA picks the first one that is appropriate for the user's preferences and machine environment.
> I agree. I think it's basically what I have described here:
> http://www.w3.org/WAI/PF/HTML/wiki/Media_TextAssociations#Resource_selection_algorithm
> . Let me know if that captures it.

seems it would be more natural to say if a track is in a trackgroup, that it is enabled if the trackgroup is enabled.

example.  I think I want to write:
<trackgroup media="accessibility(captions:yes") >
  <track src="fr.srt" lang="fr"/>
  <track src="de.srt" lang="de" />

and not
<trackgroup  >
  <track src="fr.srt" lang="fr" media="accessibility(captions:yes")/>
  <track src="de.srt" lang="de" media="accessibility(captions:yes") />

and certainly not
<trackgroup  >
  <track src="fr.srt" lang="fr" media="accessibility(captions:yes")/>
  <track src="de.wav" lang="de" media="accessibility(audiodescription:yes") />

since the semantics of trackgroup is exclusive; surely therefore the "do you want it at all" question applies only ever to the whole group?

David Singer
Multimedia and Software Standards, Apple Inc.
Received on Friday, 19 February 2010 18:46:24 UTC

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