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

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Thu, 12 May 2011 10:13:48 +1000
Message-ID: <BANLkTinW8PmrHrKFzBM4m9nvD0=ZuX_RNQ@mail.gmail.com>
To: David Singer <singer@apple.com>
Cc: John Foliot <jfoliot@stanford.edu>, HTML Accessibility Task Force <public-html-a11y@w3.org>, James Craig <jcraig@apple.com>, Michael Cooper <cooper@w3.org>
On Thu, May 12, 2011 at 8:48 AM, David Singer <singer@apple.com> wrote:
> 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>
>>> 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">

I think that would be wrong. The sighted user doesn't gather from the
placeholder frame that it is a movie trailer. Rather, they see what is
in the image. We could, however, just use "A Clockwork Orange", that
would still be appropriate because that is the text on the placeholder

>   <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.

We have had the discussion in the call if it should be @alt rather
than @aria-label. I am not opposed to it. I took @aria-label by
recommendation from a blind screenreader developer. But it seems also
from today's discussion that @aria-label is a confusing attribute name
and might tend to encourage people to provide a label for the video.
Similarly, @alt may be confusing since people may want to provide a
summary of the video content, which is not what it should contain.

I'm barely trying to go there, but .. maybe we should call this
@posteralt just to make sure people only describe the content of the
placeholder frame. In this case, however, neither @alt nor @aria-label
attribute are allowed on the video: @posteralt would replace them and
would behave like @alt, just under a different name. Or we could call
it @aria-poster to stick with the naming scheme of new accessibility

Received on Thursday, 12 May 2011 00:14:36 UTC

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