The W3C’s Timed Text Markup Language standard (TTML) and the SMPTE’s Timed Text standard (SMPTE-TT) are both free to the public, and enable captions created for television broadcast to be easily used on programs distributed over the internet.
The incompatibility of various caption file formats was once one of the chief impediments to providing captions for online video. This was a situation that needed to be rectified urgently when legislation was introduced in the US in 2010 which made it compulsory to caption online videos which had previously been captioned for TV. In 2012, the Federal Communications Commission designated SMPTE-TT as the ‘safe harbor’ standard which could be used to ensure that captions are compatible with different systems.
For more information, see our Video on demand page.
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