Rationale

For those who are deaf or hard of hearing, audio content is not accessible. Videos without descriptions are not accessible to the blind. In both cases, the information needs to be provided in an alternative format. These alternative formats are also used frequently by those who have hardware or environmental limitations. For example, the captions on a video can be selected when the audio would be distracting to others in the area or the area is too noisy the hear the audio.

Be aware that Section 508 requires that equivalent alternatives for any multimedia presentation be synchronized with the presentation. If the product is to be used by or sold to the U.S. government, for example technical support sites, the equivalent alternative (such as captions and audio descriptions of the video) must be synchronized with the presentation.


Techniques

The following techniques and examples support Checkpoint 4 from the IBM Web Accessibility Checklist.

In an accessible site, a distinction is made between a transcript and a description of multimedia content. Descriptions and transcripts can be on the same page, on a separate page, or on a page with a listing of the descriptions of all significant clips on the site. The current convention is to create a hyperlink to the transcript and description near the multimedia clip or to integrate the description into an available track of the multimedia content.

One of the following techniques is the minimum required for audio content:

The following technique is recommended to enhance the accessibility of audio content:

One of the following techniques is the minimum required for video content:

Using WGBH's Media Access Generator (MAGpie), authors can add captions once and save them to three multimedia formats: Apple's QuickTime, the World Wide Web Consortium's Synchronized Multimedia Integration Language (SMIL) and Microsoft's Synchronized Accessible Media Interchange (SAMI) format. MAGpie can also integrate and synchronize audio descriptions into SMIL presentations.

For Windows Media Player use the Synchronized Accessible Media Interchange (SAMI) technology to provide synchronized captioning when producing a video.

RealPlayer allows the user to turn on or off captioning. For more information about RealPlayer visit: www.real.com/.

For additional information about media formats, tools and players that enable captions and video descriptions, see the W3C techniques on video and audio and the CPB/WGBH National Center for Accessible Media (NCAM) resources for developers of rich media. The NCAM site includes a showcase of examples of accessible rich media, with links to resources to help implement similar solutions.

Examples

The following example illustrates a transcript of speech and other sounds that enable the user to understand the audio content more clearly:

[phone rings]

Man: Are you going to answer the phone?

[phone rings]
[phone rings]
[phone rings]

Woman: No, I'm screening my calls.

[answering machine picks up in the background]

Techniques for Flash

If you wish to develop a multimedia clip using Macromedia's Flash, there are some "best practices" that can be used to optimize the accessibility of the Flash elements on the Web page:

  1. Caption audio content. For movie clips and other meaningful Flash objects, make sure that there is a full description of what is happening in the clip. Do not rely on subtitles only.
  2. Make sure there are text equivalents for non-text elements. Use the Accessibility Panel to provide text equivalents for non-text objects.
  3. Give names to graphic elements.
  4. Use the Description choice to create longer text equivalents. This is especially important for text fields.
  5. Group elements together by using the Make Child Objects Accessible choice.
  6. Hide or group looping elements together.
  7. Use color effectively. Make sure that there is enough contrast between foreground and background, avoid blinking elements, and use something other than color to communicate with the end user.
  8. Ensure that your elements function independently of particular devices. Use keyboard shortcuts to help with navigation and use ActiveX to trap focus.
  9. Use descriptions to inform the user about the status of controls and make this available to a screen reader.
  10. Make sure that elements on the Web page are accessed in a logical order. If some content needs to be hidden because elements are not on the screen, use the visibility property to hide it until it is accessed.
  11. Provide a description for a Flash movie by adding text within, or as a title attribute for, the OBJECT element which embeds the Flash movie.
  12. Use controls that mirror HTML controls. Some screen readers may not be able to read complex controls such as dials, sliders, spin buttons or tree structures.

Testing

Test the Web site to ensure that it complies with accessibility requirements.

Tools

You will not need to install any tools to test this checkpoint.

Techniques

The following techniques are required to verify that multimedia content is accessible:


Action Result
1. Manually verify there are accessible alternatives to audio content.For more information on audio and video players, see: WGBH National Center for Accessible Media. Pass:Fail:
2. Manually verify there are accessible alternatives to video content.
For more information on audio and video players, see: WGBH National Center for Accessible Media.
Pass:Fail:
3. If the Web site includes Macromedia Flash content, use a screen reader to test the Flash content for accessibility. (See the screen reader documentation for instructions on reading Flash content.) Pass:Fail:

©2001, 2008 IBM Corporation

Last updated January 17, 2008.