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Living Examples - Multimedia Synchronization
(B) Equivalent alternatives for any multimedia presentation shall be synchronized with the presentation.

All media types should contain an equivalent alternative that is synchronized with the original presentation format.

Auditory synchronization needs to accommodate users with hearing disabilities and users who access the multimedia file with a computer system or a user agent that does not contain sound capabilities.

There is technology on the market that allows the web developer or multimedia content developer to add text-to-speech, captioning, and audio descriptions (among other abilities) to some of the more popular media platforms.

Those who do not have access to such technology have sometimes captured detailed transcripts of the video's dialog and narrative into a separate HTML file, with the link being placed on the page next to or directly underneath the video element. However, it should be understood that such a transcript is not considered truly synchronized with the presentation.

Multimedia presentations need to accommodate users with visual disabilities and users who are accessing the multimedia file with a user agent that has difficulties with video plug-ins.

People with visual disabilities will be able to hear a video's dialog or narrative, but will miss out on the "play-by-play"-esque action (e.g. video footage of a sporting event or footage from a news scene) that is not described in the audio. A method that is sometimes referred to as "voice-over" is currently being used successfully by some companies involved in the home video industry: audio descriptions fill in the gaps in film dialog by describing facial expressions, body language, actions, and other visual clues.

This method is "synchronized" because the voice-overs are an actual part of the multimedia presentation, as opposed to being contained within a separate file.

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Curator: Courtney Ritz
Responsible NASA Official: Joe Stevens
Last Updated: March 6, 2009

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