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Re: [media] handling multitrack audio / video

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Sat, 4 Dec 2010 00:24:23 +1100
Message-ID: <AANLkTikzQJE1j0AE_y-DBiiYX=BeVCvECPj13hKpvqYO@mail.gmail.com>
To: Sean Hayes <Sean.Hayes@microsoft.com>
Cc: Philip Jägenstedt <philipj@opera.com>, Eric Carlson <eric.carlson@apple.com>, Geoff Freed <geoff_freed@wgbh.org>, HTML Accessibility Task Force <public-html-a11y@w3.org>, Frank Olivier <Frank.Olivier@microsoft.com>
Hmm... now we just need to throw the alternatives in webm and mp4 as
well as ogg format into this...

Incidentally, according to
http://www.w3.org/TR/2005/REC-SMIL2-20050107/smil-content.html#q5 ,
the <switch> element also just takes the first acceptable element,
which is no different to the way in which <source> works. We probably
would want to redefine that to pick the most appropriate one rather
than the first acceptable one.

I'm hoping we can find a simpler markup though, to be honest.

Right now I am trying to think out of the box - how about considering
something like a manifest file that would simply list all the
available alternatives with their uses similar to a m3u8 file. This
would probably be just for one per format (ogg/webm/mp4) and in would
be nice if the browser decided which one to take.

Silvia.


On Fri, Dec 3, 2010 at 10:14 PM, Sean Hayes <Sean.Hayes@microsoft.com> wrote:
> Well at the risk of channeling Dick Bulterman:
>
>  <...>
>      <switch syncmaster >  <!-- this element selected from this group provides the timing -->
>         <video src=" mainMovieOC.ogg " systemSubtitle  systemLanguage="zh-Hant"  ... />   <!-- this has open subtitles in trad chinese-->
>         <video src="mainMovie.ogg" ... />   <!-- the default with no constraints -->
>    </switch>
>      <switch>
>         <video src=" transMovieBSL.ogg " systemLanguage="sgn-GB"  ... />   <!-- a BSL sign language translation to be synced to the main movie-->
>         <video src="transMovieASL.ogg" systemLanguage="sgn-US"   ... />   <!-- an ASL sign language translation to be synced to the main movie -->
>    </switch>
>     <switch>
>      <audio src="mainMovie.en.mp3" systemAudioDesc systemLanguage="en" ... />   <!-- alternate described soundtracks in a variety of languages -->
>      <audio src="mainMovie.nl.mp3" systemAudioDesc systemLanguage="nl" ... />
>      <audio src="mainMovie.de.mp3" systemAudioDesc  systemLanguage="de"  ... />
>    </switch>
>    <switch>
>       <text src="movie-sub-en.rtx" systemLanguage="en  systemCaptions ... /> <!-- alternate text tracks for subtitles and captions -->
>       < text src="movie-sub-de.rtx" systemLanguage="de" systemSubtitle ... />
>       < text src="movie-sub-nl.rtx" systemLanguage="nl" systemSubtitle  ... />
>    </switch>
>  </...>
>
> You might need to shuffle things around a bit to fit in HTML, and you could replace the systemXXX attributes with media queries.
>
> -----Original Message-----
> From: public-html-a11y-request@w3.org [mailto:public-html-a11y-request@w3.org] On Behalf Of Philip Jägenstedt
> Sent: 03 December 2010 10:01
> To: Silvia Pfeiffer; Eric Carlson
> Cc: Geoff Freed; HTML Accessibility Task Force; Frank Olivier
> Subject: Re: [media] handling multitrack audio / video
>
> 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 13:25:16 GMT

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