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Digital/Internet/MPEG Captioning
Oregon's Deaf and Hard of Hearing Services (ODHHS)-Technical Assistance Center
ODHHS Information and Technical Assistance Series
Digital/Internet/MPEG Captioning
(Source: Gary Robson, Cheetah Systems)
Can captioning be done on the Internet?
Yes, it can. At least one company (Cheetah Broadcasting) is doing this. Realtime captions are created during a live event, and then transmitted through a Web page, Internet Chat (IRC), iChat, WebChat, America Online, CompuServe, or some similar online system. This can be done for radio programs including the audio.
Can digital (MPEG) movies be captioned?
There is currently no standard for captioning in MPEG files, and no place in the file designated to hold the captions. SMPTE (Society of Motion Picture/Television Engineers) has formed a committee to handle this, and when the committee comes up with a technical solution, vendors will start implementing ways to do it.
Within SMPTE, the Committee on Multimedia Technology (M21) has a working group called "Closed Captioning & Subtitles (M21.22). Further information can be found at SMPTE´s web site, http://www.smpte.org.
You may find both the EIA-708 standard and Microsoft´s SAMI (Synchronized Accessible Media Interchange) proposal pertinent to this question.
Are there encoders available for digital formats?
Several manufacturers have encoders for D2, which typically cost about $2,000 more than the traditional NTSC encoders. There is at least one D1 encoder available as well.