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

From: Maciej Stachowiak <mjs@apple.com>
Date: Fri, 03 Dec 2010 12:27:15 -0800
Cc: 'Martin Kliehm' <martin.kliehm@namics.com>, 'Silvia Pfeiffer' <silviapfeiffer1@gmail.com>, 'HTML Accessibility Task Force' <public-html-a11y@w3.org>
Message-id: <0D7479E9-369D-4EB2-804C-9D9791E7C9CD@apple.com>
To: John Foliot <jfoliot@stanford.edu>

On Dec 3, 2010, at 12:17 PM, John Foliot wrote:

> 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.

Why is that better than including that text in the video summary?

It seems like the poster frame and your suggested label/summary text both serve the same purpose - helping the user decide if they want to play the video. They are auxiliary content. Describing the poster frame seems like an overly literal-minded approach to equivalent content. What is needed is a summary of the video that equally allows non-sighted users to decide if they want to play it, just as the poster frame (whether explicit or built-in) does for sighted users. That could include a literal description of the poster frame, if that's a helpful piece of information.

Regards,
Maciej
Received on Friday, 3 December 2010 20:27:53 GMT

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