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Questions regarding animation requirements in UAAG 1.0

From: Ian Jacobs <ij@w3.org>
Date: Wed, 21 Feb 2001 23:40:00 -0500
Message-ID: <3A949820.45B61FD8@w3.org>
To: pschmitz@microsoft.com, aaron.m.cohen@intel.com, clilley@w3.org
CC: w3c-wai-ua@w3.org, dd@w3.org, asgilman@iamdigex.net
Patrick, Aaron, Chris,

I would greatly appreciate your comments on the questions below, to
help the User Agent Guidelines Working Group resolve some outstanding
last call issues. The questions are about user agent control of
animations. 

(I am cc'ing Al Gilman and Daniel Dardailler on this email so that
 WAI PF can track this discussion if necessary.)

In the 26 Jan 2001 draft of the User Agent Accessibility Guidelines
1.0 [1], there are two checkpoints that involve control of animations:

 --------

  4.4 Allow the user to slow the presentation rate of audio, video and
  animations. For a visual track, provide at least one setting between
  40% and 60% of the original speed. For a prerecorded audio track
  including audio-only presentations, provide at least one setting
  between 75% and 80% of the original speed. When the user agent
  allows the user to slow the visual track of a synchronized
  multimedia presentation to between 100% and 80% of its original
  speed, synchronize the visual and audio tracks. Below 80%, the user
  agent is not required to render the audio track. The user agent is
  not required to satisfy this checkpoint for audio, video and
  animations whose recognized role is to create a purely stylistic
  effect.  [Priority 1]

  4.5 Allow the user to stop, pause, resume, fast advance, and fast
  reverse audio, video, and animations that last three or more seconds
  at their default playback rate. The user agent is not required to
  satisfy this checkpoint for audio, video and animations whose
  recognized role is to create a purely stylistic effect. [Priority 1]

 --------

The UA Working Group has questions about whether a user agent can
satisfy these requirements for all classes of animation and animation
format.

1) It would seem that for animations that are composed of "frames"
   (e.g., animated GIFs, Flash animations), that this type of
   control: slow, reverse, advance, etc. is feasible.

2) It would seem that for some other classes of animations
   (e.g., animations that may be created with SMIL Animation [2]),
   it may not be feasible to satisfy our slow, advance, and
   reverse requirements.

Questions:

 * Would you agree with these two assertions? 

 * Can you help us understand (and qualify) why SMIL Animation
   animations do not lend themselves to being slowed, reversed, or
   fast advanced (and how we might explain that in our requirements,
   if necessary)? Chris indicated that SMIL 2.0 animations [3] were 
   different than SMIL Animation and could be controlled in the
   indicated manner. Why is that the case?

 * What other classes of animations should we be considering and
   have forgotten about? 

Notes:

 a) We explicitly do not require user agents to provide the indicated
    control for animation effects created through scripts. Our
    checkpoints 4.4 and 4.5 only address those animation effects 
    that the user agent can "recognize" through the format.

 b) We are not concerned here with control limitations due to
    streaming (i.e., you can't fast advance through streamed content).
 
 c) We are not concerned here with alternative content workarounds
    from the author.

Thank you for any direction you can provide,

 - Ian

[1] http://www.w3.org/WAI/UA/WD-UAAG10-20010126/
[2] http://www.w3.org/TR/2000/WD-smil-animation-20000731
[3] http://www.w3.org/TR/smil20/

-- 
Ian Jacobs (jacobs@w3.org)   http://www.w3.org/People/Jacobs
Tel:                         +1 831 457-2842
Cell:                        +1 917 450-8783
Received on Wednesday, 21 February 2001 23:40:27 GMT

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