Re: [media] change proposals for issue-152

On Mar 30, 2011, at 5:03 PM, Silvia Pfeiffer wrote:

> On Wed, Mar 30, 2011 at 4:03 PM, Mark Watson <watsonm@netflix.com> wrote:
>> Sylvia wrote (sorry if formatting messes up - copied from archives)...
>> 
>> So, I think it would probably be better if instead we recommend that
>> if you wanted to use in-band tracks, you should use media fragment
>> addressing, such as:
>> 
>>    <!-- in-band german sign language track -->
>>    <video id="v3" timeline="v1" kind="signing" srclang="gsg"
>> label="German Sign Language">
>>      <source src=“video.webm#track=video_gsg” type=”video/webm”>
>>      <source src=“video.mp4#track=video_gsg” type=”video/mp4”>
>>    </video>
>> 
>> What do people think?
>> 
>> This is fine for addressing and controlling in-band tracks, but how do I
>> *discover* them in the first place. I need to get a list of the tracks and
>> their kinds and names so that I can decide what choices to offer the user
>> (assuming I am providing my own controls).
>> ...Mark
> 
> If the author expressly places all in-band tracks into <audio> and
> <video> elements, then they would be exposed in this way.
> 

The author doesn't necessarily know what in-band tracks will be present - e.g. what languages, accessibility streams etc. - or their names. People write pages which play content from all over - usually they just have a URL to start from.

...Mark

> 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...
> 
> Cheers,
> Silvia.
>

Received on Thursday, 31 March 2011 00:08:53 UTC