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Re: Requirements for external text alternatives for audio/video

From: Geoff Freed <geoff_freed@wgbh.org>
Date: Mon, 29 Mar 2010 07:23:26 -0400
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>, Sean Hayes <Sean.Hayes@microsoft.com>
CC: Laura Carlson <laura.lee.carlson@gmail.com>, Eric Carlson <eric.carlson@apple.com>, HTML Accessibility Task Force <public-html-a11y@w3.org>, Matt May <mattmay@adobe.com>, Philippe Le Hegaret <plh@w3.org>
Message-ID: <C7D605EE.BA5B%geoff_freed@wgbh.org>
On 3/28/10 7:18 PM, "Silvia Pfeiffer" <silviapfeiffer1@gmail.com> wrote:

On Mon, Mar 29, 2010 at 7:38 AM, Sean Hayes <Sean.Hayes@microsoft.com> wrote:
> I don't disagree with the need to provide appropriate alternatives to media, but the mechanism of providing a transcript is perhaps not best provided through the mechanism of trapping captions. As you say, captions would in fact probably not be an adequate replacement for the media without the text of description being included at minimum. Thus a transcript is more like the alt text on an image, a different semantic beast than captions, and probably better provided by other means.
>
> I think there is an important larger issue here. Is the text mechanism intended to provide captions and subtitles; or is the intention, as Silvia's examples would seem to suggest, to use it turn HTML5 into a time based media like SMIL or HTML+TIME.   If the latter, and this mechanism is intended to address corporate branding and advertising, then I think we are straying out of the remit of accessibility into something much larger which would need to be taken up in the wider group.

The two examples that you are providing are two extremes:
captions/subtitles on the one end, and SMIL/HTML+Time on the other.
Right now and for the purposes of this group we are focused on
captions/subtitles. But already with the features of DFXP there is a
possibility to go a step further, without going all the way to the
complexity of SMIL/HTML+Time - which, IMO, needs to come in at a
different level.

What I was describing is simply time-aligned text that is a bit more
capable than just being plain text. In particular I am talking about
hyperlinks, which are essentially nothing more than styled text, but
provide Web functionality - something that should be very important to
us in the given context. This has nothing to do with going all the way
to SMIL/HTML+Time. It is still no more than captions or subtitles, but
with the possibility of linking out at a given time.

Think about it: we could have captions that allow us to explain things
further - e.g. a movie about a historic event with names of people
mentioned and you could click through on the names of the people and
find out what they were really like and why they are portrayed as they
are in the movie. Directly related "supplementary material" - not
banned to another resource as it currently is in DVDs. Actually
available at your fingertip when you are interested in it.

Or we could have captions of a political discussion with links to
explain some background on the speakers.

Or we could have captions that would link to a dictionary entry for
words that are used very infrequently in a language.

Or, of course, we could have links in ads to the eCommerce site of the
current ad, so we can directly go and purchase the product.

GF:  I wouldn't argue against any of these cases, and in fact would argue that some of examples Silvia mentions have advantages for people with learning disabilities who rely on captions for clarification or other purposes.  But Sean may have a point- this may be something for the wider HTML 5 group to deal with, not necessarily the accessibility group.  I'd have to give it some thought.


This is not difficult to do on top of what we have right now, but
requires the ability to at least interact with links inside timed
text.

Note that I am not even sure if current DFXP/TTML supports hyperlinks,
but if it doesn't I would be very keen on introducing them because
they are extremely useful. Since DFXP/TTML is declared as being easily
extensible, that should not be so hard to do.

GF:  DFXP/TTML itself does not directly support hyperlinking (Sean, plz correct me if I'm wrong).  I believe the only way to do so is to use XLink, as specified in the Requirements table at http://www.w3.org/TR/ttaf1-dfxp/#requirements.

Regards,
Silvia.
Received on Monday, 29 March 2010 11:24:02 GMT

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