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Re: UAAG 2.0 guidelines for video

From: Janina Sajka <janina@rednote.net>
Date: Tue, 4 May 2010 21:56:54 -0400
To: HTML Accessibility Task Force <public-html-a11y@w3.org>, WAI-UA list <w3c-wai-ua@w3.org>, John Foliot <jfoliot@stanford.edu>
Message-ID: <20100505015654.GH2329@sonata.rednote.net>
Silvia Pfeiffer writes:
> Correction to my previous email:
> 
> The HTML5 media elements already have an attribute to control the playback rate:
> 
>            attribute float defaultPlaybackRate;
> 
> (see http://www.whatwg.org/specs/web-apps/current-work/multipage/video.html#media-elements).
> 
Well, since we're a W3C working group, I think we're looking at:
http://dev.w3.org/html5/spec/Overview.html#dom-media-playbackrate

Glad to see it's there, but not sure whether it's complete per the UAWG
requirements:
*	I don't see a supported range. UAWG wanted .5 to 2.0, which is
*	not particularly large.
*	I also believe we have a requirement for maintaining pitch
*	during the time-scale modification. Perhaps that's what the
*	editor's drft means when it says "monotonically," though I'm not
*	sure that's the best terminology.

In my opinion this will be an important feature for I18N as well as A11Y
support. For instance, anyone listening to content not in their native
language will doubtless discover enhanced comprehension by reducing
playback rate--provided pitch is maintained and no negative artifacts
are produced by the transformation.

Janina

> 
> So, my questions will only be for contrast and brightness.
> 
> Sorry about the confusion.
> 
> Regards,
> Silvia.
> 
> 
> On Wed, May 5, 2010 at 9:23 AM, Silvia Pfeiffer
> <silviapfeiffer1@gmail.com> wrote:
> > Hi Jim,
> >
> > I have read of all these requirements. It's quite an impressive list
> > and will certainly be useful to John as he is putting together the
> > requirements list discussed in the last phone conference of the media
> > a11y subgroup in the HTML5 a11y TF.
> >
> > I believe that most of these requirements are already being taken care
> > of or are in development - much of it is not yet present in browsers,
> > but that is more an implementation issue than a specification issue.
> > It is probably important for this group to continue to monitor
> > progress on these issues and to remind browser vendors to implement
> > these required features.
> >
> > I am, however, concerned about the  following two requirements, since
> > they are fundamental requirements on media resources that are not
> > regarded in today's HTML5 media elements and I am not aware of any
> > plans to introduce them.
> >
> >
> > On Wed, May 5, 2010 at 4:50 AM, Jim Allan <jimallan@tsbvi.edu> wrote:
> >>
> >> 4.9.5 Playback Rate Adjustment for Prerecorded Content: The user can adjust
> >> the playback rate of prerecorded time-based media content, such that all of
> >> the following are true (Level A):
> >>
> >>    * The user can adjust the playback rate of the time-based media tracks
> >> to between 50% and 250% of real time.
> >>    * Speech whose playback rate has been adjusted by the user maintains
> >> pitch in order to limit degradation of the speech quality.
> >>    * Audio and video tracks remain synchronized across this required range
> >> of playback rates.
> >>    * The user agent provides a function that resets the playback rate to
> >> normal (100%).
> >
> >
> > Would it make sense to introduce an attribute on the media elements
> > that allows changing the playback rate? Or is this solely a feature of
> > the underlying media framework and thus a browser issue?
> >
> > Or in other words: is the playback rate something that we want a Web
> > page author to be able to specify or is it enough if it is a feature
> > that the Web browser provides to the user? If it is the first, we need
> > a new attribute, if it is the latter, we need to lobby the browser
> > vendors and potentially work towards introducing a recommendation into
> > the HTML5 specification that UAs should provide this functionality.
> >
> >
> >> 4.9.11 Adjust Playback Contrast and Brightness. User has ability to control
> >> the contrast and brightness of the content within the playback viewport.
> >
> > This is actually a very similar issue to the playback rate. Again, we
> > have to answer the question whether this is something that we want to
> > give the Web page author the ability to influence or just something
> > between the UA and the user.
> >
> >
> > Best Regards,
> > Silvia.
> >

-- 

Janina Sajka,	Phone:	+1.443.300.2200
		sip:janina@asterisk.rednote.net

Chair, Open Accessibility	janina@a11y.org	
Linux Foundation		http://a11y.org

Chair, Protocols & Formats
Web Accessibility Initiative	http://www.w3.org/wai/pf
World Wide Web Consortium (W3C)
Received on Wednesday, 5 May 2010 01:57:29 GMT

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