Closed Captioning

Closed captioning (CC) is a text track encoded with a video signal that viewers can switch on or off, distinguishing it from open captions, which are permanently burned into the picture. Beyond dialogue, captions typically include speaker labels, sound effects (e.g., [applause], [door slams]), and music cues, making broadcast and streaming content accessible to deaf and hard-of-hearing audiences as well as viewers in sound-restricted environments.

The technology originated in the United States in the early 1970s through work at PBS and the National Bureau of Standards, with the first regularly captioned programs broadcast in 1980 via the National Captioning Institute. In the analog era, captions were transmitted on Line 21 of the NTSC vertical blanking interval under the EIA-608 standard. Digital television adopted CEA-708, which supports multiple languages, font choices, and positioning.

Captioning is regulated in many jurisdictions. In the U.S., the Television Decoder Circuitry Act of 1990 required caption decoders in TV sets 13 inches or larger, and the Telecommunications Act of 1996 plus FCC rules progressively mandated captioning of most broadcast programming. The 21st Century Communications and Video Accessibility Act (CVAA) of 2010 extended obligations to internet-delivered video that previously aired on U.S. television. The UK's Ofcom sets caption quotas for licensed broadcasters, and the EU's Audiovisual Media Services Directive requires member states to ensure progressive accessibility.

Captions differ from subtitles, which traditionally translate dialogue for hearing viewers and omit non-speech audio, though streaming platforms increasingly blur the distinction. They also differ from SDH (Subtitles for the Deaf and Hard-of-Hearing), a hybrid format common on DVDs and Blu-rays.

For researchers and MUN delegates, captioned archives of UN proceedings, parliamentary debates, and press briefings are valuable primary-source tools, often searchable via the caption text itself.