[whatwg] Thoughts on video accessibility

David Singer singer at apple.com
Fri Jul 17 00:13:42 PDT 2009

At 8:36  +1000 17/07/09, Silvia Pfeiffer wrote:

>I just noticed that the "media" attribute is already part of the
>"source" element definition in HTML5. I wonder which browsers have
>implemented this attribute.
>After having looked at http://www.w3.org/TR/css3-mediaqueries/, my
>understanding is that media queries specify the different presentation
>media that the html page's different stylesheets were built for and
>thus allow choosing between these stylesheets through the "link"
>element and its "media" attribute where the query goes. Also, IIUC,
>the list of presentation media is currently restricted to 'print',
>'screen' , 'aural', 'braille', 'handheld', 'print', 'projection',
>'screen', 'tty', 'tv', and 'all' and the queries cover only the
>features width, height, device-width, device-height, orientation,
>aspect-ratio, device-aspect-ratio, color, color-index, monochrome,
>resolution, scan, and grid.
>This is different for the "source" elements though: instead of
>specifying different presentation media and choosing between
>stylesheets, the "media" attribute specifies different user
>requirements and chooses between video source files. This makes it
>independent from CSS, IIUC.
>Is the intention to extend the specification of "media queries" to
>include generic means of selecting between alternative files to load
>into a HTML page? Is there a W3C activity that actually extends the
>media queries to audio and video files?
>If this is the case, it could also be used for the associated "text"
>elements that Ian and I discussed earlier in this thread. The
>alternatives there would be based on a combination of languages and
>the different categories of time-aligned text. The language would
>choose between different text files to load, and the text category
>would choose between different default styles to apply.
>I can imagine that that would work, but has anyone started extending
>existing media query specifications for this yet?

you have it.  I was wondering aloud whether media queries could be 
used to express this kind of presentation need; it's not such a 
stretch from "screen and print are different" to "screen and braille 
are different" to "plain screen and sub-titled screen are 

I am thinking aloud here, you understand.  But I think a *framework* 
for media accessibility "this is what can work, using features in 
HTML, CSS, media engines, scripting, etc." is important to work out. 
Getting basic captions working is important, but it should not be a 
one-off, but part of a conscious effort to treat accessibility as an 
integral part of the design.
David Singer
Multimedia Standards, Apple Inc.

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