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Media

Provide user controls

Give users the following types of controls for all playable files: Play, Pause/Resume, Stop, Rewind, Fast Forward and Volume. QuickTime video and sound files automatically provide these controls. If you use other types of media formats, you may need to design the controls yourself. Animated GIFs are usually presented with no user controls. In general, provide Play and Stop functions by using a scripting language.

Provide text equivalents for visual and auditory content

To make your site accessible to users with vision and hearing impairments, provide text and/or audio descriptions of visuals, and transcripts (word-for-word text versions) plus descriptions of audio content. Many people cannot use video, images, or sound, but they can use equivalent information provided via other media. The equivalent text or audio descriptions should convey the same information as the video or audio content.

Use the right technique for providing accessible multimedia:

• For images and animation, use alt text to provide a brief description, and the longdesc attribute to provide explanations longer than a sentence or two. Longdesc provides an invisible link read by screen readers to a detailed description located on a different Web page.

• For audio and video, provide a hyperlink to a trascript plus a description near the play button or link to the clip. Descriptions should generally be longer than transcripts because they need to descibe the setting and action.

• For Java applets, provide alt text, and if the applet uses the OBJECT element, provide text descriptions within the element.

Inform users of the content and size of media objects

Instructions for downloading media objects should include the file size, the media type, and a description of the subject matter. For video clips, you can provide a static, interlaced thumbnail image with alt text for screen readers. This information will help users determine whether they want to wait for the download.

Use animations to attract attention

Create animations that enhance explanation

Use repetitive loops sparingly

Animation or sound loops are efficient because they can run continuously without adding to file sizes. However, they can become irritating or distracting. Knowing how to design a media loop well requires judgment and sensitivity to the situation. Test to make sure that users are comfortable with your media loops and consider enabling users to stop the loop.