An alternative for time-based media or audio description of the prerecorded video content is provided for synchronized media, except when the media is a media alternative for text and is clearly labeled as such.
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Rationale
The purpose of this checkpoint is to provide a way for blind or visually impaired people to access the visual information that is provided in multimedia, and for a hearing impaired of deaf user to access the information in multimedia presentation. The visual information is either provided in an audio description or in a full multimedia text alternative.
The first option is to provide an audio description which complements the existing audio track with information that a blind or visually impaired person would not otherwise be able to access. During pauses in the existing audio track, a narrator describes the important visual details that are that are not already explained in the soundtrack.
The second option to meet this checkpoint is to provide a full multimedia text alternative. A full multimedia text alternative describes everything that is happening in the multimedia, and is not limited to the pauses in dialogue. In addition to the visual information, the text alternative also includes a transcript of all dialogue. The text alternative includes textual representations of all of the video, audio, and interaction from the multimedia, so that a blind or visually impaired user has the same information as a sighted user.
People who are deaf, are hard of hearing, or who are having trouble understanding audio information for any reason can read the text presentation as well.
Required development techniques
Compliance with this checkpoint requires all the following technique to be met.
This technique is defined in the WCAG 2.0 Level A Success Criterion for item 1.2.3 (link resides outside of ibm.com).
- Audio descriptions: Provide audio descriptions of video, or a full multimedia text alternative including any interaction that presents equivalent information for prerecorded multimedia.
Examples for General developers
1. Audio descriptions: Provide audio descriptions of video, or a full multimedia text alternative including any interaction that presents equivalent information for prerecorded multimedia.
To comply with this technique, at least one of the following examples must be implemented.
Example 1
Provide a full text alternative for an audio-only file, such as a podcast.
Hearing impaired users may not be able to listen to a podcast (or any other audio only format). Providing a transcript ensures full access to the content of the audio-only file for all users. The transcript must identify the speakers and include descriptions of any other sounds heard (such as sound effects).
Example 2
Provide a full text alternative for a video-only file.
An example of a video-only content would be a training module that captures a software demonstration. This is very common in IBM, when a tool like Camtasia or Simulation Producer is used to record and playback the actions that take place on the user's computer, without added audio. Other examples include silent movies or an animation with no sound.
A full text alternative of the file would describe, in text, exactly what is happening on the screen. All mouse clicks, screen shots, and images should be described, as well as any interaction or other information that is being conveyed in the video.
Example 3
Provide an audio description of a video-only file.
An audio description would of the video would server as an alternate format for a blind user. The audio description should describe everything that is happening in the video file, and should be available either as a separate, downloadable file, or be synchronized with the video.
Example 4
Provide a sound track that includes an audio description.
- Providing a sound track that includes audio description as the primary sound track.
The National Center for Accessible Multimedia, which is part of the Media Access Group at WGBH, maintains a small multimedia clip that shows the opening to the movie "The Lion King". The clip contains audio description (as well as captions). Please visit the NCAM site to play the video clip (link resides outside of ibm.com), and to hear the audio descriptions in use. If this were the only version of the movie available, it would satisfy this example. - Providing a sound track that includes audio description AND associating it with the synchronized media content. This technique is also demonstrated by the Lion King example above. The audio description was added to the original soundtrack during pauses in the dialogue. The original version of the movie is still available without audio description.
For additional information, refer to WCAG 2.0 examples for providing a sound track that includes audio description (link resides outside of ibm.com).
Example 5
Provide a full synchronized media text alternative including any interaction.
A full multimedia text alternative will allow a person to experience all of the video information, audio information, and interaction that the multimedia presents, in an alternative format. An example of this (using the Lion King example above) would be to provide a text alternative a movie, which would be very much like a screenplay, modified to exactly match what happens on the screen. The alternative would include everything that would be found in a transcript, along with the text from the audio description, sounds, scene changes, character expressions, and additional descriptive text if necessary.
For additional information, refer to WCAG 2.0 examples for providing a full multimedia text alternative including any interaction (link resides outside of ibm.com).
Required test techniques
The following test tools and techniques are required to test this checkpoint.
Test tools:
Install the following tools to test this checkpoint:
Required accessibility verification test techniques:
Use the following accessibility verification test (AVT) techniques to validate the Web content. It is recommended that these tests be performed in order.
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Test the Web site with a Web syntax analyzer to verify the compliance criteria as follows:
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Verify the compliance criteria for the type of multimedia that applies as per instructions below.
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Verify the following compliance criteria with a screen reader.
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Pass:
Fail:
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©2009 IBM Corporation
Last updated May 28, 2009.
W3C Recommendation 11 December 2008: http://www.w3.org/TR/WCAG20/ (link resides outside of ibm.com)
Copyright 1994-2009 W3C (Massachusetts Institute of Technology, European Research Consortium for Informatics and Mathematics, Keio University), All Rights Reserved.