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

From: <bugzilla@jessica.w3.org>
Date: Tue, 12 Oct 2010 22:30:13 +0000
To: public-html-a11y@w3.org
Message-Id: <E1P5nML-0000lq-6e@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=10642

--- Comment #52 from Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no> 2010-10-12 22:30:10 UTC ---
(In reply to comment #51)

> > To reuse @alt

> That would indicate that @alt is an alternative text for the video element,

HTML5 decides what @alt on <video> means.  @alt would anyhow only be a short
alternative text - if the video or audio indeas is very short (perhaps it only
demos how pronounce a hard German word, for instance), then @alt could be
enought, I guess.

Understanding @alt as a practical "textual substitute"( see Vlad Alexander [1])
rather than a full textual description, would in my view be helpful also for
<video>.
[1] http://rebuildingtheweb.com/en/offer-to-save-longdesc/

@alt, by the way, has a strong connection to images: in <img alt=*>, <area
alt=*>, <input type="image" alt=*> it is connected to images, in some form. So
I am not as pessimitic that authors will "jump to conclusions" about what @alt
means. (The only place in HTML4 were it is not linked to images is for the
<applet> element.)

> which it's not - the @title fulfills that role, IIUC.

Question:  If the @src of <video> is bogus, or if the @poster attribute is
bogus,  or if the user agent is textual, then how would suggest that the
element should be represented? 

To me it seems logical if @alt then would display.  @title never displays
unless you activate it somehow. Besides, it doesn't make sense to me to give
@title any different semantics for <video> than it has for <img> - for <img>,
then it offers additional information, perhap it contains copyright or creator
info and so on.

> What I wanted to point
> out is that there is a need for both, an alternative short text for the video
> element and another one for the image. If @alt and @title satisfy that, fine.
> But I think it may confuse authors as to the role that @alt plays, since in
> other elements is the alternative text for the element, not for an attribute
> therein.


I think what is needed is this: @poster as well as @alt should be defined the
same way. As you put it "The alt texts are input  into making the decision to
view the video, just like the poster is for people  with sight." 

Unless you meant to suggest that @alt should contain a "textual substitute" for
the very content of the video itself, then thtere is at leaste no technical
problem, right. I agreee that @title eventually could contain info about the
video itself. 

As I see it, the link between @alt and poster image should not be too stron,
just as the link between the @alt in <area> and its image map image is also not
"too strong": it is the practical issues that matter. E.g. the @alt in an
<area> does not describe in detail the part of the image that it is connected
to - it usually consentrates on describing the link which <area> contains.

The author must decide: would a direct description of the image frame that
@poster contains be the best way to attract attention to the movie? Or would
some other description do it better? Often videos can be used in place of
images, e.g. in news articles - the poster will serve an illustrative role in
itself. In those case I think it would make sense to let the @alt contain a
description of the image - especially if the scene is telling.

PS: If "textual substitute" is equal to an "in your face" textual replacment
(unlike @title, which is optional), and if you are interested in in having one
textual substitute representation for the "video itself", as well as another
textual substitute representation for the "poster image itself", then  I don't
think it would be overkill to use an <img> elment for poster. (But if we don't
need more than one textual substitute representation of the video, then I think
@alt is perfect.)

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Received on Tuesday, 12 October 2010 22:30:14 GMT

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