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Re: Requirements for external text alternatives for audio/video

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Fri, 26 Mar 2010 07:50:22 +1100
Message-ID: <2c0e02831003251350i4eec57dew79f288bbdd88ffd3@mail.gmail.com>
To: Eric Carlson <eric.carlson@apple.com>
Cc: Geoff Freed <geoff_freed@wgbh.org>, HTML Accessibility Task Force <public-html-a11y@w3.org>, Matt May <mattmay@adobe.com>, Philippe Le Hegaret <plh@w3.org>
Hi Eric,

On Fri, Mar 26, 2010 at 2:46 AM, Eric Carlson <eric.carlson@apple.com> wrote:
>
> On Mar 24, 2010, at 9:29 PM, Silvia Pfeiffer wrote:
>
> In summary - I would suggest keeping the File Format requirement at
> http://www.w3.org/WAI/PF/HTML/wiki/Media_TextAssociations#File_Formats
> with supporting both, srt and dfxp (or ttml as Sean clarified).
>
>   What DFXP profile are you suggesting we mandate?
>   As Maciej noted [1], even the presentation profile requires XSL-FO. Does
> anyone actually think it is reasonable to require a UA to implement this
> substantial spec just to style captions?
> eric
> [1] - http://lists.w3.org/Archives/Public/public-html-a11y/2010Mar/0103.html

I believe right now all we need to mandate is the required part of the
minimum profile
(http://www.w3.org/TR/ttaf1-dfxp/#profile-dfxp-presentation) - it
would conform with WCAG and be extensible to the other features that
will certainly be mandated in the future. It looks to me that if other
profiles are necessary beyond the ones already given in the TTML
specification, these can be developed at a later stage.

Right now we need to take care to find a way to deal with the style
and layout specifications. I agree with Sean that this should be done
not by implementing the TTML specifications directly, but by mapping
them to existing HTML/CSS/JavaScript constructs.

Philippe's demos is at http://www.w3.org/2009/02/ThisIsCoffee.html
with the original TTML file at
http://www.w3.org/2009/02/ThisIsCoffee61_captions.xml and the
JavaScript that interprets it at
http://www.w3.org/2008/12/dfxp-testsuite/web-framework/HTML5_player.js.
The test suite is at
http://www.w3.org/2008/12/dfxp-testsuite/web-framework/START.html
which demonstrates support (or lack of support) for each TTML feature
- choose the HTML5 player to see what mappings are already supported.

These mappings that are currently done in JavaScript have to be
extracted into a specification document. And we need to make sure when
we implement support for captions that we can add the features parsed
out of TTML into the HTML document.

Cheers,
Silvia.
Received on Thursday, 25 March 2010 20:51:15 GMT

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