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.
On this page:
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 or deaf user to access the information in a multimedia presentation. The visual information should be described either in audio format or in a full multimedia text alternative.
An audio description complements the existing audio track with information that a blind or visually impaired person would not otherwise know. During pauses in the existing audio track, a narrator describes the important visual details that are not already explained in the soundtrack.
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, as well as textual representations of all of the video, audio, and interaction from the multimedia. This enables a blind or visually impaired user to have the same information as a sighted user.
People who are deaf, hard of hearing, or have trouble understanding audio information can read the text presentation as well.
Required development and unit test techniques
To comply with this checkpoint, you must either meet techniques 1, 2 and 3 defined below, OR you must meet technique 4.
- For video with audio: Provide audio descriptions of video including any interaction that presents equivalent information for prerecorded multimedia.
- For audio-only: Provide an alternative for time-based media that presents equivalent information for prerecorded audio-only content.
- For video-only: Provide either an alternative for time-based media or an audio track that presents equivalent information for prerecorded video-only content.
- Media alternative: Provide a full multimedia text alternative.
Note: The examples presented in the techniques are not exhaustive. They are meant to illustrate the spirit of this checkpoint.
To comply with this technique, you must implement at least one of the following examples.
General example 1
Provide a soundtrack that includes an audio description.
For additional information, refer to the WCAG 2.0 examples of providing a second user-selectable audio track that includes audio descriptions (link resides outside of ibm.com).
General example 2
Provide a transcript 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.
General example 3
Provide an audio description of a video-only file. An audio description of the video would serve as an alternative format for a blind user. The audio description should describe everything that is happening in the video and should be available either as a separate downloadable file or it should be synchronized with the video.
General example 4
Provide a full text alternative for a video-only file. An example of video-only content would be a training module that captures a software demonstration. It is very common for a tool to be used to record and play back 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.
General 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, audio, and interaction that the multimedia presents, but in an alternative format. Using the Lion King example above, you could provide a text alternative to a movie, which would be very much like a screenplay, only modified to match exactly 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 the WCAG 2.0 examples of providing an alternative for time-based media (link resides outside of ibm.com).
Required unit tests for general development techniques 1-5
Manually perform the following unit tests.
©2011 IBM Corporation
Last updated July 1, 2011.
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.