W3C home > Mailing lists > Public > public-html-a11y@w3.org > March 2012

Re: CP, ISSUE-30: Link longdesc to role of img [Was: hypothetical question on longdesc]

From: David Singer <singer@apple.com>
Date: Wed, 21 Mar 2012 14:15:39 -0700
Cc: Sean Hayes <Sean.Hayes@microsoft.com>, John Foliot <john@foliot.ca>, 'Silvia Pfeiffer' <silviapfeiffer1@gmail.com>, "'xn--mlform-iua@målform.no'" <xn--mlform-iua@xn--mlform-iua.no>, "rubys@intertwingly.net" <rubys@intertwingly.net>, "laura.lee.carlson@gmail.com" <laura.lee.carlson@gmail.com>, "mjs@apple.com" <mjs@apple.com>, Paul Cotton <Paul.Cotton@microsoft.com>, "public-html-a11y@w3.org" <public-html-a11y@w3.org>, "public-html@w3.org" <public-html@w3.org>
Message-id: <C4EEDD2B-5BB4-44DE-B483-33E5771008AF@apple.com>
To: "janina@rednote.net" <janina@rednote.net>

On Mar 21, 2012, at 13:59 , janina@rednote.net wrote:

> David Singer writes:
>> Or we simply say the obvious "If the image is not a representative frame of the video, or conveys information in addition to the content of the video, then a description of that information must also be included with the description(s) of the video that are supplied for accessibility (e.g. alt, longdesc, transcript, etc.)."
> A description of the video is not the same thing as a description of a
> rich image that is published to stand for the video.
> It's not a video until the video is running.

It's not a video when it is paused for any reason, at any time.  And when it is paused, the image is *unpredictable* because it's paused at an indeterminate point.  That's a characteristic of paused videos, they look like images when time is not advancing. Any initial paused state is just one of those paused states.

> Until then it's an icon for
> the video, or a poster for the video, or the magic doo-hickie that tells
> you something about the video (or not).

Actually, it's a frame of the video. You left out the 90%+ case.  Have a look at a very typical usage (where I, alas, can't watch the video): <http://www.bbc.co.uk/news/world-europe-17457845>.  That image is just a better initial place-holder than the first frame - which hasn't been fetched yet, when the page loads.

There is some history here.  QuickTime movies have a field in their header "poster time" - the time of the image to show as the initial image, when the first frame was unsuitable (e.g. because it's black, or the typical trailer green-frame). Clearly in the HTML case we were looking for something to show while loading the resource, so indexing into the resource was not suitable.

Occasionally, in QuickTime, people wanted to author custom frames (to be clearer, for example, or juxtapose some elements that didn't come together in any single frame of the video); for them, we provided custom poster frames as well.

> Two different things, semantically disparate. Therefore, they obviously
> need semantically distinct description.

This is an assertion that does not reflect that the media element is a single element, which needs a description.

> This should be obvious,

It ought to be obvious that a paused video looks like an image.  But apparently it's not.

It ought to be obvious that we should have, long ago, had non-timed provision for the video itself.  Short text? No. Description? No. Link to a transcript? Um, not yet.

Instead, we debate how to arrange the deck-chairs. If we had already dealt with the major problems, spending time on this as a tidy-up might be warranted; even then, all it takes is saying that the image must be included in the alternative(s) to the element (description(s), transcript, etc.).

David Singer
Multimedia and Software Standards, Apple Inc.
Received on Wednesday, 21 March 2012 21:16:08 UTC

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