Re: [media] alt technologies for paused video (and using ARIA)

On May 11, 2011, at 6:50 , Silvia Pfeiffer wrote:

>>> 
>>> 1. To satisfy use case 1: @aria-label
>> (http://www.w3.org/WAI/PF/HTML/wiki/Media_Alt_Technologies#Example_1:_A_Cl
>> ockwork_Orange)
>> 
>>  <video poster="media/ClockworkOrangetrailer.jpg" controls
>>         aria-label="A Clockwork Orange movie poster">
>>    <source src="media/ClockworkOrangetrailer.mp4">
>>    <source src="media/ClockworkOrangetrailer.webm">
>>    <source src="media/ClockworkOrangetrailer.ogv">
>>  </video>
>> 
>> RESPONSE:
>> This is a mistaken use of aria-label: this <video> (object) is not a
>> poster, it is the entire media offering - a multi-media resource that deaf
>> users, blind users, and deaf/blind users will consume differently based
>> upon the additional resources that the author provides.
> 
> I have come to this text by discussion with several people, including
> several blind developers of screen readers, so I don't think this is a
> mistaken use of aria-label. In fact, my examples actually had longer
> text in @aria-label and I was told to make them shorter because blind
> users don't want to have to wait until the end of reading-out of the
> label before being told additional information about the element.
> 
> Note how my proposal clearly states that this text is only relevant
> when the video is not on autoplay. This is because in this situation
> the video is represented by the placeholder image, which in this case
> is the Clockwork Orange movie poster. When the video plays, the alt
> text is not relevant because we have an audio track playing and audio
> descriptions. So, when autoplay is turned off and a screenreader moves
> onto this element, the screenreader needs to share with the blind user
> exactly what the sighted users are seeing, which is the placeholder
> image.
> 
> Also, note how I am deliberately not talking about a poster frame,
> because we are not providing accessibility information to the user
> about the markup, but about the rendering. Since there is no
> difference to the sighted user when looking at the video element
> whether the frame is extracted from the video file or from a separate
> resource, this is not something that a blind user needs to be told
> about either.

I think the point is that the poster and the aria-label are both about the video (they are peers) so it might be better to say

 <video poster="media/ClockworkOrangetrailer.jpg" controls
        aria-label="A Clockwork Orange movie trailer">
   <source src="media/ClockworkOrangetrailer.mp4">
   <source src="media/ClockworkOrangetrailer.webm">
   <source src="media/ClockworkOrangetrailer.ogv">
 </video>

> 
> It's a label for the video element, which in the instance of
> non-autoplay is simply the content of the placeholder frame. So, it's
> completely correct.
> 

I think it should be thought of as a label for the video in the element, whether or not it's playing.  So saying it's a poster is not true;  that would be the correct description of an image.


David Singer
Multimedia and Software Standards, Apple Inc.

Received on Wednesday, 11 May 2011 23:53:17 UTC