Web Accessibility Policy of the State of Maine
7.1 - Provide synchronized captions for multimedia containing speech.
Multimedia generally refers to recorded or live media containing both video and audio tracks. Captioning (as in "closed captioned") is essentially a text transcript of the audio synchronized with the audio/video tracks of the presentation.
Individuals who are deaf or hard of hearing may require captions to access the audio information in multimedia.
Whenever possible, captions should be implemented using Synchronized Multimedia Integration Language (SMIL) to synchronize the display of text from a transcript with the video. As a less desirable alternative, captions can be added to a standard video recording and then converted to a web format.
Ref: WCAG 1.4, 508 b
7.2 - Provide audio descriptions for multimedia with significant video.
Audio descriptions are verbal descriptions of the actions and images displayed in a video that are inserted during pauses in the regular dialog or audio track. Audio descriptions are only necessary if significant information that is presented visually is not discernable from the dialog or audio track.
Individuals who are blind or low-vision may require audio descriptions to access the visual information in multimedia.
Carefully consider whether audio descriptions are necessary to present the significant information of a multimedia recording. Many speech-intensive events, such as speeches, lectures, or conferences, may not need audio description.
Ref: WCAG 1.3