A bit about subtitles

Teletext brought along with it closed captioning, a method of relaying the speech into text for the hard of hearing/deaf. It seems teletext pioneered the service which today is more popular than ever - almost all programmes on the BBC are subtitled. Also used as a translation service (for example programmes such as S4C's Pobol y Cwm are broadcast in Welsh but have English subtitles) the method makes television more accessible to a wider range of people.

Open captioning, which existed prior to closed captioning, meant printing the actual words onto the screen. This method is often used in films as an alternative to overdubbing with voice actors. Closed captioning is submitted via teletext in the vertical line blanking interval of televisions with appropriate encoders.

BBC's new iPlayer apparently has teething problems with subtitles but once they are sorted it will be the next step in subtitling:



About.com - a history of closed captioning
Subtitles, from Wikipedia