W3C home > Mailing lists > Public > public-html-a11y@w3.org > March 2011

Re: [media] change proposals for issue-152

From: Mark Watson <watsonm@netflix.com>
Date: Wed, 30 Mar 2011 19:03:11 -0700
To: Ian Hickson <ian@hixie.ch>
CC: Silvia Pfeiffer <silviapfeiffer1@gmail.com>, "public-html-a11y@w3.org" <public-html-a11y@w3.org>
Message-ID: <0D41871A-EFA6-4D9F-933C-435944F6CC6A@netflix.com>


Sent from my iPhone

On Mar 30, 2011, at 6:16 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.
> 

For video too, it is useful to discover in-band tracks from the resource. I may have a resource URL and not know whether it contains a single video track or multiple (e.g. Sign language tracks or video with burned in captions). I'd like to discover what's there and then create video elements for the ones I want to render.

This possibility exists for in-band text tracks in the existing spec and several of the proposals extend it to audio and video in-band tracks. I think it's an essential feature.

...Mark

> -- 
> Ian Hickson               U+1047E                )\._.,--....,'``.    fL
> http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
> Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
> 
Received on Thursday, 31 March 2011 02:04:22 UTC

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