Re: <video> accessibility

On Mon, 17 Sep 2007, Henri Sivonen wrote:
> 
> The spec already says that the fallback is not for old browsers. I think 
> it should drive the point even more explicitly and say it isn't for 
> accessibility alternatives in <video>-aware UAs and that accessibility 
> should be handled in the video itself.

(I assume the "not" in the first sentence is extraneous.)

I've added a note to this effect in the audio and video sections.


> Closed audio descriptions for the blind could be handled using an additional
> sound track. However, whereas captions are negligible in data size compared to
> the video track, additional soundtracks may be large enough to make content
> providers hesitate to always serve them. Points that seem to need research:
>  * Can Speex compress audio descriptions enough to be negligible compared to
> the video track so that content providers could be comfortable with always
> muxing in the audio description?
>  * If not, how to handle audio descriptions as an optional HTTP download?
> Should there be a separate audio file or an entire alternative video file?
>  * Would it be feasible to encode the descriptions as timed text and feed them
> to a speech synthetizer on the client? (Does any off-the-shelf timed media
> framework even support this sort of thing?)

I would like to see implementation experience in this area. Apple have 
proposed using new media queries for allowing the user agent to select an 
appropriate media track, which seems like a good direction to follow.


> For closed captioning, it would be good to have at least a note pointing 
> to information on how to flag an Ogg Writ track as closed captions so 
> that authors and UAs are more likely to get the same understanding of 
> what constitutes closed captions. (This may have to wait until later in 
> the development of HTML5 and Writ.) Likewise for closed audio 
> descriptions muxed in the main file, it would be good to have a note on 
> how to flag an audio track as being a closed description track.

I agree. I welcome any feedback from people who have any suggestions along 
these lines -- my own expertise is inadequate for completing this section.

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

Received on Friday, 19 October 2007 02:01:39 UTC