UAAG 2.0 guidelines for video

The UAAG Guidelines[1] in their present form are organized by basic
principles that, when applied as a whole, provide guidance in ensuring that
a user agent and the (accessible) content it renders, and provides
interaction with, is accessible.  As such, specific guidelines that apply to
multimedia, or as we call it, time-based media, rendering and interaction
are found across several of the principles.  This document is a first pass
at extracting the guidelines of relevance to the media accessibility
subgroup.  Feedback on these guidelines, as well as the overall UAAG
document is welcome. The UAAG Implementation document [2] is also available
for review.


PRINCIPLE 2. Facilitate programmatic access

2.1.1 Platform Accessibility Architecture: Support an platform accessibility
architecture relevant to the operating environment.
(Level A)

2.1.2 Name, Role, State, Value, Description: 2.1.2 Name, Role, State, Value,
Description: For all user interface components including the user interface,
rendered content, and alternative content, make available the name, role,
state, value, and description via an platform accessibility architecture.
(Level A)

2.1.3 Accessible Alternative: If a feature is not supported by the
accessibility architecture(s), provide an equivalent feature that does
support the accessibility architecture(s). Document the equivalent feature
in the conformance claim. (Level A)

2.1.4 Programmatic Availability of DOMs: If the user agent implements one or
more DOMs, they must be made programmatically available to assistive
technologies. (Level A)

2.1.5 Write Access: If the user can modify the state or value of a piece of
content through the user interface (e.g., by checking a box or editing a
text area), the same degree of write access is available programmatically.
(Level A)

2.1.6 Properties: If any of the following properties are supported by the
accessibility platform architecture, make the properties available to the
accessibility platform architecture: (Level A)

(a) the bounding dimensions and coordinates of rendered graphical objects
(b) font family of text
(c) font size of text
(d) foreground color of text
(e) background color of text.
(f) change state/value notifications

2.1.7 Timely Communication: For APIs (for non-web-based user agents)
implemented to satisfy the requirements of this document, ensure that
programmatic exchanges proceed at a rate such that users do not perceive a
delay. (Level A).

PRINCIPLE 3: Perceivable - The user interface and rendered content must be
presented to users in ways they can perceive

3.1.1 Identify Presence of Alternative Content The user has the ability to
have indicators rendered along with rendered elements that have alternative
content (e.g. visual icons rendered in proximity of content which has short
text alternatives, long descriptions, or captions). In cases where the
alternative content has different dimensions than the original content, the
user has the option to specify how the layout/reflow of the document should
be handled. (Level A).

3.1.2 Configurable Default Rendering: The user has a global option to
specify which types of alternative content by default and, in cases where
the alternative content has different dimensions than the original content,
how the layout/reflow of the document should be handled. (Level A)

3.1.3 Browse and Render: The user can browse the alternatives, switch
between them, and render them according to the following (Level A):

   1. synchronized alternatives for time-based media (e.g., captions, audio
descriptions, sign language) can be rendered at the same time as their
associated audio tracks and visual tracks, and
   2. non-synchronized alternatives (e.g., short text alternatives, long
descriptions) can be rendered as replacements for the original rendered
content.

3.1.4 Rendering Alternative (Enhanced): Provide the user with the global
option to configure a cascade of types of alternatives to render by default,
in case a preferred type is unavailable. If the alternative content has a
different height or width, then the user agent will reflow the viewport.
(Level AA)

3.6.1 Configure Text:  The user can globally set the following
characteristics of visually rendered text content, overriding any specified
by the author  or user agent defaults (Level A):

    * (a) text scale (i.e., the general size of text) ,
    * (b) font family, and
    * (c) text color (i.e., foreground and background).

PRINCIPLE 4. Ensure that the user interface is operable

4.1.1 Keyboard Operation: All functionality can be operated via the keyboard
using sequential or direct keyboard commands that do not require specific
timings for individual keystrokes, except where the underlying function
requires input that depends on the path of the user's movement and not just
the endpoints (e.g., free hand drawing). This does not forbid and should not
discourage providing mouse input or other input methods in addition to
keyboard operation. (Level A)

4.9.2 Time-Based Media Load-Only: The user has the option to load time-based
media content @@DEFINE@@ such that the first frame is displayed (if video),
but the content is not played until explicit user request. (Level A)

4.9.5 Playback Rate Adjustment for Prerecorded Content: The user can adjust
the playback rate of prerecorded time-based media content, such that all of
the following are true (Level A):

    * The user can adjust the playback rate of the time-based media tracks
to between 50% and 250% of real time.
    * Speech whose playback rate has been adjusted by the user maintains
pitch in order to limit degradation of the speech quality.
    * Audio and video tracks remain synchronized across this required range
of playback rates.
    * The user agent provides a function that resets the playback rate to
normal (100%).

4.9.6 Stop/Pause/Resume Multimedia: The user can stop, pause, and resume
rendered audio and animation content (including video and animated images)
that last three or more seconds at their default playback rate. (Level A)

4.9.6 Navigate Multimedia: The user can navigate along the timebase using a
continuous scale, and by relative time units within rendered audio and
animations (including video and animated images) that last three or more
seconds at their default playback rate. (Level A)

4.9.7 Semantic Navigation of Time-Based Media. The user can navigate by
semantic structure within the time-based media, such as by chapters or
scenes, if present in the media (AA).

4.9.8 Track Enable/Disable of Time-Based Media. During time-based media
playback, the user can determine which tracks are available and select or
deselect tracks. These selections may override global default settings for
captions, audio descriptions, etc.


4.9.9 Sizing Playback Viewport: User has the ability to adjust the size of
the time-based media up to the full height or width of the containing
viewport, with the ability to preserve aspect ratio and to adjust the size
of the playback viewport to avoid cropping, within the scaling limitations
imposed by the media itself. (Level AA)

4.9.10 Scale and position alternative media tracks. User has ability to
scale and position alternative media tracks independent of base video.
(Level AAA)

4.9.11 Adjust Playback Contrast and Brightness. User has ability to control
the contrast and brightness of the content within the playback viewport. 

1. http://www.w3.org/WAI/UA/2010/ED-UAAG20-20100430/
2. http://www.w3.org/WAI/UA/2010/ED-IMPLEMENTING-UAAG20-20100430/ 

Jim Allan, Accessibility Coordinator & Webmaster
Texas School for the Blind and Visually Impaired
1100 W. 45th St., Austin, Texas 78756
voice 512.206.9315    fax: 512.206.9264  http://www.tsbvi.edu/
"We shape our tools and thereafter our tools shape us." McLuhan, 1964

Received on Tuesday, 4 May 2010 20:07:13 UTC