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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 07:47:52 +0000
To: public-html-bugzilla@w3.org
Message-Id: <E1PHtn6-0004Oi-Ud@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=10642

--- Comment #76 from Silvia Pfeiffer <silviapfeiffer1@gmail.com> 2010-11-15 07:47:51 UTC ---
(In reply to comment #75)
> > However, my argument is not that we do not need a text alternative for the
> > poster. I do argue that we need that. But I also argue that when we have a text
> > replacement for the video, we can include the text replacement for the poster
> > in that piece of text - it does not have to be separate.
> 
> It does have to be separate, because the purpose of the poster and the purpose
> of the video content are distinct. For one thing, the poster could be content
> not found in the video, like rendered text of the video's title. For another,
> the poster itself serves the purpose of arousing interest among users in
> playing the video.
> 
> People who can't see still want to know _why_ this content is important before
> playing it. If that information is not important enough for a blind user, then
> it should follow that it provides no meaningful information to a sighted user.
> In which case, @poster should be removed, because it adds no value to HTML5. Of
> course none of that is true, which is why the issue was raised.
> 
> Worse, proposing to use one field for these distinct purposes is something that
> doesn't really belong in the specification. It indicates we're not making a
> technical decision, but rather just routing around damage. It's the kind of
> advice that belongs in WCAG techniques, but only after the HTML WG has failed
> to provide the necessary functionality for users. Half-steps like this have no
> place in the spec itself.


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. Maybe you misunderstand how the
poster is presented? It is indeed presented as a replacement for the video
imagery. It is not possible to look at the poster as a separate image - that
would defeat its purpose as a video poster image. A sighted user who does not
inspect the HTML code does not know whether this picture is from inside the
video or not, nor does he/she need to know. Whatever is shown looks to the user
like it is part of the video - and it could come from inside the video or not.
So, what is shown needs to be communicated in the text alternative for the
video. If the imagery shows text (be that from a poster or from the first video
frame), then that text should be in the text alternative for the video. If it
shows a person, then the description of that person should be in the text
alternative for the video.

I believe some of the communication problems we have here is the name of the
attribute: @poster. I believe that many people think this has something to do
with movie posters - advertising material that is being used as separate
content from the video (or rather: movie). This is not what the @poster
attribute is. The @poster attribute defines nothing more than a thumbnail for
the video and it stands in the video's place. If that thumbnail is used as a
separate resource, it would be in an <img> element and thus have all its own
text alternatives.

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Received on Monday, 15 November 2010 07:47:54 GMT

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