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Re: SMIL: draft items for UA guidelines

From: Al Gilman <asgilman@access.digex.net>
Date: Wed, 30 Sep 1998 17:04:01 -0400 (EDT)
Message-Id: <199809302104.RAA12513@access5.digex.net>
To: jbrewer@w3.org (Judy Brewer)
Cc: w3c-wai-ua@w3.org, jongund@staff.uiuc.edu, allan_jm@tsb1.tsbvi.edu, hoschka@w3.org, kerscher@montana.com, cindy.king@gallaudet.edu, robla@real.com, dick.bulterman@cwi.nl, Lloyd.Rutledge@cwi.nl, jbrewer@w3.org, Geoff_Freed@wgbh.org
to follow up on what Judy Brewer said:

> Lloyd,
> 
> Thanks very much for your comments. I'm bouncing this message to the User
> Guidelines Working Group, as well as other people cc'd on the original
> message, for additional comment, preferably by October 6.
> 
> Here are my brief comments; please excuse (or correct) my very rough
> paraphrasing of your points. I've included your complete message below. 
> 
> The original message is at
> http://lists.w3.org/Archives/Public/w3c-wai-ua/1998JulSep/0200.html if any
> one is looking for it.
 
> #3. SMIL needs to be extended to be able to handle audio
> descriptions of video images (see sample of suggested code
> below) -- Agreed, and the method you propose looks good to me,
> although I would want to be sure that it is a solution that is
> easy to implement. Could other people please review and comment
> on this - Philipp, George, Geoff? ...I also think that we need
> a mechanism for text descriptions of video images, which my
> original draft didn't deal with adequately.

That's all supposed to be there.  Consider the use of PAR to have
the video and audio play in sync, and test-variable conditions on
the audio so that it depends on whether the user wants the
description played or not.  Another way this can be programmed is
if there is already a soundtrack, one wraps the basic sound track
and the sound track with the descriptive inlay in a SWITCH so
that the user can select among them.  This is all subject to having
the logic and implementation verified that it works, but in principle
those are already possible to do.

> #8. Repositioning of captions could be handled by switch
> statements... -- Unclear here. Would captions that are overlaid
> on video media object be controllable in this manner, or is the
> idea that user preferences should require captions to be
> displayed elsewhere than on top of a video media object?

I don't recommend extending SWITCH to handle user-controlled
positioning.  It is basically a SELECT construct under a new
name.

The built-in layout capability is primitive, because the
long-term plan is to do the layout in CSS or XSL.  The user's
ability to re-position a caption display region is definitely an
interactive capability for the UA guidelines above and beyond
what the author gives you in layout.  [Note my long-term flames
that we need to take a more object-oriented view of the display
medium.]

> #9. Providing user control over presentation pace is complex
> and the following issues need to be considered... --
> Agreed. Need to consider to what extent hard synchronization is
> required among other media objects that have timing
> relationships with the audio (or perhaps video?) that is being
> pace-controlled. Comments or suggestions from anyone else on
> this?

The timing model is pretty flexible.  I think there is enough
in the basic model.  Yes, this is a topic where the UA guidelines
need to pick up on where the format definition leaves off.

Al
Received on Wednesday, 30 September 1998 17:04:10 UTC

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