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Re: [media] handling multitrack audio / video

From: Philip Jägenstedt <philipj@opera.com>
Date: Fri, 03 Dec 2010 11:01:26 +0100
To: "Silvia Pfeiffer" <silviapfeiffer1@gmail.com>, "Eric Carlson" <eric.carlson@apple.com>
Cc: "Geoff Freed" <geoff_freed@wgbh.org>, "HTML Accessibility Task Force" <public-html-a11y@w3.org>, "Frank Olivier" <Frank.Olivier@microsoft.com>
Message-ID: <op.vm4t4mi1sr6mfa@kirk>
On Thu, 02 Dec 2010 16:41:56 +0100, Eric Carlson <eric.carlson@apple.com>  
wrote:

>
> On Dec 2, 2010, at 6:31 AM, Silvia Pfeiffer wrote:
>
>>
>> For #3 there is not much to do actually - just having a means to
>> switch between resources would be sufficient. That means could be a
>> button underneath the video or a second tab with the video and lets
>> the user change between the main video and it's auditory-only
>> counterpart. I wonder if we even need special accessibility features
>> for this.
>>
> The idea we have long talked about to use media queries on a <source>  
> element to label the accessibility features of its resource could be  
> very useful here. It would allow an author to include videos with and  
> without open audio descriptions in the markup:
>
>    <video controls>
>        <source src="trailer_with_open_captions.m4v"  
> media="accessibility(audiodescription:yes)" >
>        <source src="trailer.m4v">
>    </video>
>
> and the user agent will automatically choose the captioned file if the  
> user's preferences say they want them.

Anything that overloads <source> will suffer from the problem that users  
can't switch between versions once one has been selected. The resource  
selection algorithm is already quite messy. Today, <source> is supposed to  
be used for equivalent resources where only the format differs. For  
alternative tracks, I think we really need something different. I'd say  
<track>, but that's really for *additional* tracks so far, not  
alternatives...

-- 
Philip Jägenstedt
Core Developer
Opera Software
Received on Friday, 3 December 2010 10:00:51 GMT

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