Editing Closed captioning (section)

=== Technical development of closed captioning ===
Closed captioning was first demonstrated in the United States at the First National Conference on Television for the Hearing Impaired at the University of Tennessee in Knoxville, Tennessee, in December 1971.<ref name="caphist" /> A second demonstration of closed captioning was held at Gallaudet College (now [[Gallaudet University]]) on February 15, 1972, where [[American Broadcasting Company|ABC]] and the [[National Bureau of Standards]] demonstrated closed captions embedded within a normal broadcast of ''[[The Mod Squad]]''.
At the same time in the UK the BBC was demonstrating its Ceefax text based broadcast service which they were already using as a foundation to the development of a closed caption production system. They were working with professor [[Alan Newell (English computer scientist)|Alan Newell]] from the University of Southampton who had been developing prototypes in the late 1960s.

The closed captioning system was successfully encoded and broadcast in 1973 with the cooperation of PBS station [[WETA-TV|WETA]].<ref name="caphist" /> As a result of these tests, the FCC in 1976 set aside Line 21 for the transmission of closed captions. PBS engineers then developed the caption editing consoles that would be used to caption prerecorded programs.

The [[BBC]] in the UK was the first broadcaster to include closed captions (called subtitles in the UK) in 1979 based on the [[Teletext]] framework for pre-recorded programming.

==== Real-time captioning ====
Real-time captioning, a process for captioning live broadcasts, was developed by the [[National Captioning Institute]] in 1982.<ref name="caphist" /> As developed in 1992, real-time captioning used [[stenotype]] operators who are able to type at speeds of up to 375 words per minute provide captions for live television programs, allowing the viewer to see the captions within two to three seconds of the words being spoken.

Improvements in [[speech recognition]] technology mean that live captioning may be fully or partially automated. [[BBC Sport]] broadcasts use a "respeaker": a trained human who repeats the running commentary (with careful enunciation and some simplification and [[markup language|markup]]) for input to the automated text generation system. This is generally reliable, though errors are not unknown.<ref>{{cite web|url=https://www.bbc.com/news/uk-england-tyne-41473443|title=Match of the Day 2: Newcastle subtitle error leaves BBC red-faced|date=2 October 2017|work=[[BBC Online]]|access-date=2 October 2017}}</ref>

In the 1980s, [[DARPA]] sponsored a number of projects aimed at developing automatic speech recognition software. Much of this work was done by researchers at Carnegie Mellon University. In the 1990s, this program included a novel focus of using this technology for news transcription purposes.<ref>{{cite journal|pages=191–192|title=Speech Recognition by Machine: A Review|volume=6|number=3|year=2009|journal=International Journal of Computer Science and Information Security|arxiv=1001.2267 |last1=Anusuya |first1=M. A. |last2=Katti |first2=S. K. }}</ref> Later developments have yielded live, real-time AI-based captioning generating systems.<ref>{{cite news|url=https://www.theverge.com/2025/1/9/24339817/vlc-player-automatic-ai-subtitling-translation|title=VLC player demos real-time AI subtitling for videos}}</ref>