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Re: [media] handling multitrack audio / video

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Wed, 27 Oct 2010 14:44:27 +1100
Message-ID: <AANLkTimN8onEeCkj15HizR5KPf0c6=3yAsVEgRwUZZ+R@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 27, 2010 at 2:40 PM, Silvia Pfeiffer
<silviapfeiffer1@gmail.com> wrote:
> 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/
>

Gah, just some more googling and I found it:
http://www.w3.org/TR/SMIL3/smil-timing.html#Timing-ControllingRuntimeSync
has syncMaster, but not mediaSync. Is mediaSync introduced to avoid
the use of <par> ?

Cheers,
Silvia.
Received on Wednesday, 27 October 2010 03:45:20 GMT

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