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Video Poster image (was RE: DRAFT analysis of fallback mechanisms for embedded content ACTION-66)

From: John Foliot <jfoliot@stanford.edu>
Date: Fri, 3 Dec 2010 12:17:19 -0800 (PST)
To: "'Martin Kliehm'" <martin.kliehm@namics.com>, "'Silvia Pfeiffer'" <silviapfeiffer1@gmail.com>
Cc: "'HTML Accessibility Task Force'" <public-html-a11y@w3.org>
Message-ID: <00b401cb9327$16588a20$43099e60$@edu>
Martin Kliehm wrote:
> Hi Silvia,
> On 01.12.2010 05:13, Silvia Pfeiffer wrote:
> > In fact,<video>  also doesn't have @summary or @alt.
> That's true. At least <video> has a poster image where Everett filed a
> bug and escalated an issue that an alt-text is missing. But in
> yesterday's telcon we found that an @alt for a poster image will likely
> be different from a @label (what I called @summary in my draft). Also
> it
> is debatable if a video needs even more accessible fallback content,
> like a short description or @longdesc.

In discussion with Gregory after Thursday's call, and after thinking about 
this more myself, applying an @alt attribute to the <video> is actually 
somewhat counter-intuitive, as at best the alt value would be either the 
video's title, or a similar value (in other words, not a very useful 
fallback mechanism for the embedded content). What I suspect the video 
should really have for AT use/availability would probably be more like 
@summary/<summary> and/or aria-desribedby, so that non-sighted users would 
have a better understanding of what the video (movie) is about before 
choosing to play the video. (With a nod To Eric Carlson for making me 
understand this distinction better)

The poster frame image itself however still requires an accessible fallback, 
and since it is an image (right down to the file format - .jpg, .png) it 
certainly should require an @alt value, especially if the poster image is 
not directly related to the video - the use-case example I gave was one from 
here at Stanford, where the poster image would take an alt value such as 
"...alt="Stanford University - This video is Closed Captioned"..." as this 
is the text inside the image file. (See: 
http://dev.w3.org/html5/alt-techniques/) Based upon Thursday's call (where I 
posed this very question) and in discussion with a number of non-sighted 
users already, there seems to be general consensus here.

I will continue working on my change proposal towards Everett's bug this 
weekend, and will advise when it is ready for review.

Received on Friday, 3 December 2010 20:17:59 UTC

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