W3C home > Mailing lists > Public > public-html-a11y@w3.org > April 2011

Re: text track associations

From: Eric Carlson <eric.carlson@apple.com>
Date: Wed, 13 Apr 2011 07:58:20 -0700
Cc: Ian Hickson <ian@hixie.ch>, Silvia Pfeiffer <silviapfeiffer1@gmail.com>, Mark Watson <watsonm@netflix.com>, "public-html-a11y@w3.org" <public-html-a11y@w3.org>
Message-id: <052FD786-F029-4083-9114-C20C83B12614@apple.com>
To: Sean Hayes <Sean.Hayes@microsoft.com>

On Apr 13, 2011, at 6:39 AM, Sean Hayes wrote:

> Interesting approach. It's a somewhat misnamed use of a video element to supply audio and captions but not video.
> 

Why? Like video, captions are a type of visual media.

> Audio files don't work today in two of the major browsers; and It's also far from clear to me that it the spec currently allows it, but if you say as editor it does, then I guess it could be made to work. 
> 
It never even crossed my mind that a file with only audio samples shouldn't work in a <video> element. Requiring otherwise will make it more difficult for authors to write generic script libraries and for hosting services, as it is not possible to know if most media files have video from just the MIME type of file extension.

If we require the src to a <video> element to contain visual media, what should happen with a file that can change characteristics while it is playing, eg. an adaptive stream that switches to audio-only when the user's bandwidth changes?


> I think we will need to change the spec to indicate more clearly that the <video> element is supposed to work if there is no video data supplied.
> 
> For example, change:
> "A video element is used for playing videos or movies."
> To
> "A video element is used for playing videos or movies or audio".
> 
What is the difference between a "video" and a "movie"? How about "A video element is used for playing video or audio files."


> And  replacing
> "The video element is a media element whose media data is ostensibly video data, possibly with associated audio data"
> 
> With
> "The video element is a media element whose media data is ostensibly video data, audio data or possibly video data with associated audio data."
> 
Or:
"The video element is a media element whose media data is ostensibly video or audio data, or both."


> I'm also not clear if the section on "Media elements", which is indicated to 'apply equally to video and audio', means that if I supply a video to an audio element; that is supposed to play the audio data from it?
> 

Of course. Again, requiring otherwise will make it more difficult for hosting services and script authors.


> Can I create a display rectangle with CSS for an audio element to display video data?
> 
I guess this could go either way, but I think it is more logical for an <audio> element to render only audio samples. Again from the perspective of someone writing generic script or markup, I think it is useful to be able to assume that an <audio> element won't render any visual media. 

eric
Received on Wednesday, 13 April 2011 14:58:53 UTC

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