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[media] Log of requirements changes to 2.8, 3.4, 3.5, 3.6, 3.8

From: John Foliot <jfoliot@stanford.edu>
Date: Thu, 22 Jul 2010 19:33:19 -0700 (PDT)
To: <public-html-a11y@w3.org>
Message-ID: <03c701cb2a0f$69abe4a0$3d03ade0$@edu>
Summary of edits to Media Accessibility Requirements Wiki based on
comments resolutions proposed to & accepted by Media Subteam by John
Foliot and Eric Carlson:

Sec. 2.8 Sign Translation

* Addition of the following 2 new sentences in the Introductory text: 

"Acknowledging that not all devices will be capable of handling multiple
video streams, this is a SHOULD requirement for browsers where hardware is
capable of support.  Strong authoring guidance for content creator will
mitigate situations where user-agents are unable to support multiple video
streams (WCAG) - for example, on mobile devices that cannot support
multiple streams, authors should be encouraged to offer 2 versions of the
media stream, including one with signed captions burned into the media.

Selecting from multiple tracks for different sign languages should be
achieved in the same fashion that multiple caption/sub-title files are

* Clarrification to SL-3, by adding "Parallel video here means 2 discrete
videos playing in sync with each other. It is preferable to have one
discrete <video> element contain all pieces for sync purposes rather than
specifying multiple <video> elements intended to work in sync."


Sec. 3.4 Production practice and resulting requirements.

* Addition of the following sentence to the Introductory text:

"This is primarily an authoring requirement. It is a understood that a
common time-stamp format must be declared in HTML5, so that authoring
tools can conform to a required output."

* Clarification to PP-1 by adding the following sentence: "Browsers cannot
support all forms of time-stamp formats out there, just as they cannot
support all forms of image formats (etc.). This necessitates a clear and
unambiguous declared format, so that existing authoring tools can be
configured to export finished files in the required format."

* Clarification to PP-3 by adding the following sentence: "This is again
dependent on authoring practice - if the content
creator delivers a final media file that contains related accessibility
content inside the media wrapper (for example an MP4 file), then it will
require an appropriate 3rd party authoring tool to make changes to that
file - it cannot be demanded of the browser to do so." 


Sec 3.5 Discovery and activation/deactivation of available alternative
content by the user.

Added the following sentence:
"Alternative Content must be both discoverable by the user, and accessible
in device agnostic ways. The development of APIs and User Agent controls
should follow the following UAAG design guidance:"


3.6 Requirements on making properties available to the accessibility

* Changed Explanatory Text: 
"For players running on platforms that support an accessibility API any
media controls need to be connected to that API."

"For User Agents supporting accessibility APIs implemented for a platform,
any media controls need to be connected to that API."

* Changed (API-1) - Changed the following text:
"Support to expose the alternative content tracks for a media resource to
the user, i.e. to the browser."

"The existence of Alternative Content tracks for a media resource must be
exposed to the User Agent."

* Removed "(API-4) External control devices, such as remote controls, need
to be enabled to access alternative content tracks, too." 

Justification: This is a User Agent Device Requirement; while recognizing
that this is an important requirement, the HTML5 specification should be
device agnostic.


3.8 Requirements on the parallel use of alternate content on potentially
multiple devices in parallel.

* Added the following text: 
"(A request to the UAAG on clarifications to a number of these points was
made, and a detailed response was provided. The response requires review
and integration into this document, but can be found today at:
Received on Friday, 23 July 2010 02:33:53 UTC

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