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Re: Track kinds

From: David Singer <singer@apple.com>
Date: Mon, 02 May 2011 15:22:38 -0700
Cc: Silvia Pfeiffer <silviapfeiffer1@gmail.com>, HTML Accessibility Task Force <public-html-a11y@w3.org>
Message-id: <8149B731-AC78-456C-8670-020E1DB4B05E@apple.com>
To: Mark Watson <watsonm@netflix.com>

On May 2, 2011, at 10:57 , Mark Watson wrote:

>> 
>> 2. A2 is labelled "main+description", not just "description", and B2 is labelled "alternate+description", not just "description"
>> 
> 
> This is what I suggested below although I think B2 would be labeled just "description", because it is not an alternative to B1 - it is intended to be presented together with B1.
> 
> This would expose the "alternative vs additional" property to HTML.
> 
> The remaining question would be syntactically, is "main+description" two tags, with a global convention that any number of tags can be joined with a "+" character. Or is it a single tag defined separately from "main" and "description".
> 

You are right, "alternative" (I was taught that alternating is what current does, switching back and forth, and a choice is an alternative) should be marked as meaning something other than the main content that nonetheless replaces it (e.g. a different camera angle, a different commentator).  My mistake.

By the way, an early version of this idea, which I am not sure ever hit this list, was to be explicit about what 'kind's affect what tracks, in this sense:  the components of the 'normal' presentation are initially enabled, and the other content disabled.  Instead of a plain label on each track, the label is explicitly prefixed with + (enable) or - (disable).

Then, a normally-enabled track could have a set of labels 
-captions -highcontrast
(disable this track if captions or highcontrast desires are on)
and the captions track says
+captions 
(presumably burned-in captions)
and the highcontrast track says
+highcontrast

Basically, additive tracks have the +<whatever> on them; replacement tracks also put -<whatever> on the track they replace.

Not proposing it as such here, but providing in case it's helpful, and as background.

David Singer
Multimedia and Software Standards, Apple Inc.
Received on Monday, 2 May 2011 22:23:06 GMT

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