What are Captions?
Captions are text versions of the spoken word. Captions allow the content of web audio and video to be accessible to those who do not have access to audio. Though captioning is primarily intended for those who cannot hear the audio, it has also been found to help those that can hear audio content and those who may not be fluent in the language in which the audio is presented.
Common web accessibility guidelines indicate that captions should be:
* Synchronized - the text content should appear at approximately the same time
* No standard method for displaying text synchronized with other media.
* Need for a standard Timed Text format synchronized with some other timed media.
Timed Text applications
* Subtitles of movies on the Web (foreign languages)
* Captions for people lacking audio devices or having hearing disabilities
* Karaoke
* Scrolling news, credits rolls
* TickerTape, marquee, "crawls"
* Text overlay
* TelePrompter
SMIL Interoperability
* Good interoperability on synchronization level
* Not so good interoperability for media
o Text: Plain
Why a Standardized Timed-text Format?
On the Web, there is no standard method for displaying text which is synchronized with other elements, such as video and audio. The three most popular multimedia players-- Apple's QuickTime Player, Microsoft's Windows Media Player and RealNetworks' RealPlayer-- support only their own proprietary text formats (QText, SAMI and RealText, respectively). As a result, multimedia authors must write synchronized text files in multiple formats if they wish to support more than one player. A standardized timed-text format
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