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

From: <bugzilla@jessica.w3.org>
Date: Mon, 04 Oct 2010 16:55:03 +0000
To: public-html-a11y@w3.org
Message-Id: <E1P2oJb-0004np-Pt@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=10642

--- Comment #41 from Maciej Stachowiak <mjs@apple.com> 2010-10-04 16:55:02 UTC ---
(In reply to comment #29)
> (In reply to comment #27)
> > (In reply to comment #26)
> > > This
> > > also applies to the first frame displayed if no explicit poster frame is
> > > provided. Since it's either this first frame or the explicitly linked image,
> > > covering them both the same way makes sense.
> > 
> > The trouble with providing poster alt text when no explicit poster image is
> > given is that we can't be sure that the UA will choose the first frame. It may
> > choose the middle frame, or the first non-blank frame.
> 
> Maybe in theory. But in practice all browser use the very first frame, because
> that is the first data downloaded together with the metadata. We might as well
> specify the use of the first frame for default posters in the spec if there is
> a loophole for compatibility across browsers.

It's not necessarily the first frame - some media formats allow an explicit
choice of poster frame to be embedded in the media container itself. However, I
do believe that in practice it is ubambiguous what the poster frame will be and
this is unlikely to vary among implementations.

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Received on Monday, 4 October 2010 16:55:06 GMT

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