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[Bug 10642] No alternative text description for video key frame (poster)

From: <bugzilla@jessica.w3.org>
Date: Mon, 04 Oct 2010 19:47:46 +0000
To: public-html-a11y@w3.org
Message-Id: <E1P2r0k-0005p5-3b@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=10642

--- Comment #42 from John Foliot <jfoliot@stanford.edu> 2010-10-04 19:47:44 UTC ---
(In reply to comment #39)
> I wonder if this is a confused proposal.  The poster frame is an alternative to
> the video, before it's playing/loaded.  Surely we should have
> a) short alternative text for the audio/video
> b) a link to a transcript
> c) a link to a long description
> 
> of the multimedia itself, not the proxy for it?

"The poster  attribute gives the address of an image file that the user agent
can show while no video data is available.

Note: The image given by the poster attribute, the poster frame, is intended to
be a representative frame of the video (typically one of the first non-blank
frames) that gives the user an idea of what the video is like."
- http://dev.w3.org/html5/spec/Overview.html#attr-video-poster

We have 2 problems: If I cannot see the 'image' that the poster frame displays,
how do I know "what the video is like"?

While the spec suggests that @poster is 'intended' to be a representative frame
of the movie, it is not however forbidden that the image in question can in
fact be *any* image, and the fact that authors can specify *any* image leaves
open the door that not only can they, they likely will.  For this reason we
must ensure that when they do so, they can so so in an accessible fashion.

If the poster frame is the first frame of a movie, then likely the short
alternative text for the audio/video is sufficient, however if the replacement
image is not a frame of the video than alternative text that tells non-sighted
users what the image conveys is required.

I think that enough use-cases have been brought forward to show where there is
a need, thus the only question remains: how do we achieve this? More than one
person has championed a new attribute: @posteralt

* Is there a technical reason why we cannot have this attribute in HTML5? 
* A philosophical reason that trumps the accessibility requirement? 
* Are there any other alternative proposals?

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Received on Monday, 4 October 2010 19:47:49 GMT

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