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Re: Accessibility of <audio> and <video>

From: Laura Carlson <laura.lee.carlson@gmail.com>
Date: Wed, 15 Oct 2008 13:21:46 -0500
Message-ID: <1c8dbcaa0810151121sab4a013o780dab5d8d68b340@mail.gmail.com>
To: "Patrick H. Lauke" <redux@splintered.co.uk>
Cc: "W3C WAI-XTECH" <wai-xtech@w3.org>, "HTML WG" <public-html@w3.org>, html4all <list@html4all.org>

Hi Patrick,

You wrote [1]:

> What's the error handling of a video or audio that lacks natively embedded
> alternatives, closed captions, etc?

It doesn't seem that the spec currently addresses that specifically.
Regarding video error handling the spec says:

<quote
cite="http://www.w3.org/TR/html5/video.html#video">

...the user agent may provide messages to the user (such as
"buffering", "no video loaded", "error", or more detailed information)
by overlaying text or icons on the video or other areas of the
element's playback area, or in another appropriate manner.

User agents that cannot render the video may instead make the element
represent a link to an external video playback utility or to the video
data itself.

User agents should provide controls to enable or disable the display
of closed captions associated with the video stream, though such
features should, again, not interfere with the page's normal
rendering.

User agents may allow users to view the video content in manners more
suitable to the user (e.g. full-screen or in an independent resizable
window). As for the other user interface features, controls to enable
this should not interfere with the page's normal rendering unless the
user agent is exposing a user interface. In such an independent
context, however, user agents may make full user interfaces visible,
with, e.g., play, pause, seeking, and volume controls, even if the
controls attribute is absent.

User agents may allow video playback to affect system features that
could interfere with the user's experience; for example, user agents
could disable screensavers while video playback is in progress.

</quote>

Regarding video fallback the spec currently says:

<quote
cite="http://www.w3.org/TR/html5/video.html#video">

Content may be provided inside the video element. User agents should
not show this content to the user; it is intended for older Web
browsers which do not support video, so that legacy video plugins can
be tried, or to show text to the users of these older browser
informing them of how to access the video contents.

In particular, this content is not fallback content intended to
address accessibility concerns. To make video content accessible to
the blind, deaf, and those with other physical or cognitive
disabilities, authors are expected to provide alternative media
streams and/or to embed accessibility aids (such as caption or
subtitle tracks) into their media streams.

</quote>

Regarding audio fallback the spec currently says:

<quote
cite="http://www.w3.org/TR/html5/video.html#audio">

Content may be provided inside the audio element. User agents should
not show this content to the user; it is intended for older Web
browsers which do not support audio, so that legacy audio plugins can
be tried, or to show text to the users of these older browser
informing them of how to access the audio contents.

In particular, this content is not fallback content intended to
address accessibility concerns. To make audio content accessible to
the deaf or to those with other physical or cognitive disabilities,
authors are expected to provide alternative media streams and/or to
embed accessibility aids (such as transcriptions) into their media
streams.

</quote>

[1] http://lists.w3.org/Archives/Public/public-html/2008Oct/0045.html

Best Regards,
Laura

-- 
Laura L. Carlson
Received on Wednesday, 15 October 2008 18:22:22 GMT

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