Typical applications of timed text are the real time subtitling of foreign-language movies on the Web, captioning for people lacking audio devices or having hearing impairments, karaoke, scrolling news items or teleprompter applications.
The W3C is developing a Timed Text (TT) specification that covers many aspects of timed text on the Web. It has been adopted as a W3C Recommendation.
The issue of developing an interoperable timed text format came up during the development of the SMIL 2.0 specification. Today, there are a number of incompatible formats for captioning, subtitling and other forms of timed text used on the Web. This means that when creating a SMIL presentation, the text portion often needs to be targeted to one particular playback environment. This poses an issue for creating interoperable SMIL presentations. Moreover, the accessibility community relies heavily on captioning to make audiovisual content accessible to a hearing-impaired audience. The lack of an interoperable format adds a significant additional cost to the costs of captioning Web content, which are already high.
Timed Text enriches the user experience for services involving timed text, and is seen as an important stimulus for instance in the usage of captioning and subtitling. The organizations willing to work on Timed Text include vendors of streaming multimedia technology, web browser companies, representatives of the accessibility community, caption content producers and consumer electronics companies.