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

From: <bugzilla@jessica.w3.org>
Date: Mon, 15 Nov 2010 08:44:13 +0000
To: public-html-a11y@w3.org
Message-Id: <E1PHufd-00069Y-Rr@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=10642

--- Comment #78 from Silvia Pfeiffer <silviapfeiffer1@gmail.com> 2010-11-15 08:44:10 UTC ---
(In reply to comment #77)
> (In reply to comment #76)
> > I do not follow your argument for why they need to be separate. The purpose of
> > the poster or displayed video frame is to express something that will make
> > people want to watch the video. It is therefore not distinct, even it if
> > contains content that is not in the video.
> 
> It is distinct, in that it is presented before the video itself would be
> played.


When there is no @poster, there is also an image that is presented before the
video is played. It makes no sense not to have a description for that either.
They are both part of the video experience and therefore logically part of the
video's text alternative.

>  I can see a definite advantage to having the poster's alternate text
> specified separately from the video content's: it allows the poster alternate
> text to be queried separately.

That would be the only reason why I could see a necessity for a separate
@posteralt, as I said before. But I honestly cannot see a use case where it
would be necessary to have the @poster attribute's display retrieved separately
from the user when it is part of the video (of course it would be required when
it was displayed separately in an <img>, but that's not the case here).

In particular can I not see this additional alternative representation of the
video being read out by the screen reader.


>  This would in fact bring the experience closer
> to that of the sighted user, namely, that the poster can be presented
> separately first, enticing the user to play the video.
> 
> Of course it may be that the first few sentences of the video content's
> alternate text does this job.  But it may not.

So, let's think this through. What would realistically be in a @posteralt that
would not be in a normal @alt (or @aria-label) for a video? The @alt would
realistically contain a description of the image being shown as a replacement
for the video. What else? It cannot provide a summary of the video, since that
would be more than the sighted user gets. That kind of content would come
through a @aria-describedby or the time-synchronized video description track
that we are preparing for. So, realistically, the @alt (or @aria-label)
contains exactly what the @poster shows. Nothing more and nothing less.

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Received on Monday, 15 November 2010 08:44:15 GMT

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