Re: UAAG 2.0 guidelines for video

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.

Received on Tuesday, 4 May 2010 23:24:38 UTC