Movies, videos and animations often include audio content. This could be a voice over, important or dialogue subtitles in a translated film. You should provide captioning or text transcripts which present the same information as the audio or video and make sure they are synchronized with the multimedia presentation.
Text transcripts are simply textual equivalents of sounds. When these transcripts are presented synchronously with a video presentation, they are called captions and are used by people who cannot hear the audio track of the video material.
You can provide equivalents for sounds by a link to a text transcript or description of the sound file. The link to the transcript should appear in a highly visible location such as at the top of the page.
Some media formats (e.g. QuickTime 3.0 and SMIL) allow you to add captions and video descriptions to the multimedia clip. SAMI allows you to add captions.
Here is an example that shows captions for a scene where the phone rings and then is answered.
[phone rings]
[ring]
[ring]
Hello?"
Until the format you use supports alternative tracks, make two versions of the movie available, one with captions and descriptive video and one without.