B. Equivalent alternatives for any
multimedia
presentation shall be synchronized with the presentation.
Explanation:
Providing equivalent information for
inaccessible content is one of the primary ways authors can make
their documents accessible to people with disabilities.
What is meant by equivalent?
- For graphic and audio information this
would be a text equivalent, which should convey
all essential content. Text content can be presented to the user
as synthesized speech, Braille, and visually-displayed text.
- Non-text equivalents
(e.g., an auditory description of a visual presentation, a video
of a person telling a story using sign language as an equivalent
for a written story, etc.) also improve accessibility for people
who cannot access visual information or written text, including
many individuals with blindness, cognitive disabilities,
learning disabilities, and deafness.
Equivalent information may be provided in a
number of ways, including through attributes (e.g., a text value for
the "alt" attribute in HTML and SMIL), as part of element content
(e.g., the OBJECT in HTML), as part of the document's prose, or via
a linked document (e.g., designated by the "longdesc" attribute in
HTML or a description link). Depending on the
complexity of the equivalent, it may be necessary to combine
techniques (e.g., use "alt" for an abbreviated equivalent, useful to
familiar readers, in addition to "longdesc" for a link to more
complete information, useful to first-time readers).
A text transcript is a text
equivalent of audio information that includes spoken words and
non-spoken sounds such as sound effects. A caption is
a text transcript for the audio track of a video presentation that
is synchronized with the video and audio tracks. Captions are
generally rendered visually by being superimposed over the video,
which benefits people who are deaf and hard-of-hearing, and anyone
who cannot hear the audio (e.g., when in a crowded room
For use on Windows based platforms, the Media
Access Generator, MAGpie, is an authoring tool
for making video and multimedia materials accessible to persons with
disabilities. It provides an environment for authors who want to add
captions, subtitles and audio descriptions to their work. It’s
available from the CPB/WGBH National Center for Accessible Media
(NCAM):
http://ncam.wgbh.org/Webaccess/magpie/
Examples:
A text transcript is a text
equivalent of audio information that includes spoken words and
non-spoken sounds such as sound effects.
A caption is a text transcript
for the audio track of a video presentation that is synchronized
with the video and audio tracks. Captions are generally rendered
visually by being superimposed over the video, which benefits people
who are deaf and hard-of-hearing, and anyone who cannot hear the
audio (e.g., when in a crowded room).
A collated text transcript
combines (collates) captions with text descriptions of video
information (descriptions of the actions, body language, graphics,
and scene changes of the video track). These text equivalents make
presentations accessible to people who are deaf-blind and to people
who cannot play movies, animations, etc. It also makes the
information available to search engines.
One example of a non-text equivalent is an
auditory description of the key visual elements of a
presentation. The description is either a prerecorded human voice or
a synthesized voice (recorded or generated on the fly). The auditory
description is synchronized with the audio track of the
presentation, usually during natural pauses in the audio track.
Auditory descriptions include information about actions, body
language, graphics, and scene changes.
See National Center for Accessible Media (http://ncam.wgbh.org/richmedia/examples/index.php)
for examples of equivalent
alternatives for any multimedia presentation.
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Creating Accessible Web Sites
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