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Re: [media] change proposals for issue-152

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Thu, 31 Mar 2011 12:49:20 +1100
Message-ID: <AANLkTi=JMW9gJmUBQJ00Yj1Wg92ZHraXThv_3YsDXq51@mail.gmail.com>
To: Ian Hickson <ian@hixie.ch>
Cc: Mark Watson <watsonm@netflix.com>, "public-html-a11y@w3.org" <public-html-a11y@w3.org>
On Thu, Mar 31, 2011 at 12:16 PM, Ian Hickson <ian@hixie.ch> wrote:
> On Wed, 30 Mar 2011, Silvia Pfeiffer wrote:
>>
>> However, for in-band audio and video elements that are not exposed in
>> this way, that is certainly an issue. Such tracks would just be exposed
>> and displayed by the browser they cannot be controlled from JavaScript
>> unless listed in a slave <audio> or <video> element. So, since it is in
>> the control of the author to expose them, it is probably sufficient.
>>
>> For example: to get all the audio tracks that have been exposed in slave
>> audio elements for a video with id="v1", you would do:
>>
>> audioTracks = new Array[];
>> index = 0;
>> for (i in document.getElementsByTagname("audio")) {
>>   if (i.timeline == "v1") {
>>     audioTracks[index] = i;
>>     index++;
>>   }
>> }
>>
>> Not elegant, but it works...
>
> Video is harder since it involves assigning a playback region, so I agree
> with the reasoning above for video tracks, more or less. But for audio
> tracks it seems exposing them is fine. That's what both Microsoft's
> proposal and the MediaController proposal do.


Hmm are you suggesting to explicitly expose an audioTracks IDL
attribute that has this information? It would be possible... would it
contain only in-band tracks? Are the audioTracks and videoTracks IDL
attributes of the MediaController API in fact only exposing in-band
tracks?

Incidentally, I don't quite buy into the ExclusiveTrackList /
MultipleTrackList choice for audio and video tracks in the
MediaController API. I think both video and audio tracks should be
allowed to have multiple of them active at the same time. For example,
for video, it would be the main video and a sign language track and
maybe a different camera angle, too. I wonder what reasons you had to
make video tracks exclusive.

Cheers,
Silvia.
Received on Thursday, 31 March 2011 01:50:12 UTC

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