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Re: [media] handling multitrack audio / video

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Wed, 27 Oct 2010 14:40:46 +1100
Message-ID: <AANLkTi=2A-TsoSjp_O_kOLtvi+05NqungUjSf0zjBZcL@mail.gmail.com>
To: Daniel Weck <daniel.weck@gmail.com>
Cc: public-html-a11y@w3.org, Fabien Cazenave <fabien.cazenave@inria.fr>, Gylling Markus <markus.gylling@gmail.com>, DeMeglio Marisa <marisa.demeglio@gmail.com>
On Wed, Oct 20, 2010 at 9:34 AM, Daniel Weck <daniel.weck@gmail.com> wrote:
> Hi Silvia, with regards to your proposal [1]:
>
> I think that solution #3 doesn't need to rely on the "par" time container.
> As you know, introducing new markup elements with timing semantics into
> HTML5 is likely to raise the acceptance threshold, so I would like to
> suggest an alternative solution based on a new synchronization attribute.
>
> There is an actively-developed experimental W3C SMIL Timesheet
> implementation [2] that proposes syncMaster (boolean) and mediaSync (IDREF)
> attributes to mark HTML content in order to specify an explicit timebase
> (other than the default one implied by the Timesheet scheduler) for the
> playback of timed continuous media.
>
> Inspired by this mechanism, here is a refactoring of your example (please
> note that I actually prefer "syncMaster" to "mediaSync", but that's merely a
> syntactic sugar issue, so for consistency purposes I'll use the attribute
> just like it is used in the Timesheet implementation proposal):
>
> <video id="v1" controls> <!-- primary content -->
> ...SOURCE(s) and TRACK(s)
> </video>
> <audio controls mediaSync="v1"> <!-- pre-recorded audio descriptions -->
> ...SOURCE(s)
> </audio>
> <video controls mediaSync="v1"> <!-- sign language overlay -->
> ...SOURCE(s)
> </video>
>
> --- Note that the "mediaSync/syncMaster" attribute would modify the playback
> and seeking behavior of the media elements to which it is applied.
> Consequently, I think it would be necessary to specify that the "controls"
> attribute would be overridden (to false) *and* that the JavaScript control
> API would be disabled so that the playback of the supplemental audio and
> video (as per your example) would depend entirely on the "master" media
> object.
>
> Because of the simple nature of this proposal (coarse synchronization), I
> think it would help a great way towards supporting pre-recorded audio
> descriptions (as opposed to textual ones already supported by the track
> element) and sign-language overlay in HTML5.
>
> Let me know what you think.
> Cheers, Dan
>
> [1]
> http://lists.w3.org/Archives/Public/public-html-a11y/2010Oct/0520.html
>
> [2]
> http://labs.kompozer.net/timesheets/audio.html#htmlMarkup
> http://labs.kompozer.net/timesheets/video.html#htmlMarkup
>

I've just checked the specification of SMIL Timesheets [1] and wasn't
able to find either a mediaSync or a syncMaster attribute. Is that
something that Kompozer introduces or is that specified somewhere
else, too?

Thanks,
Silvia.

[1] http://www.w3.org/TR/timesheets/
Received on Wednesday, 27 October 2010 03:41:41 GMT

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