Close captioning

Closed captioning (CC) and subtitling are both processes of displaying text on a television, video screen, or other visual display to provide additional or interpretive information. Both are typically used as a transcription of the audio portion of a program as it occurs (either or in edited form), sometimes including descriptions of non-speech elements. Other uses have been to provide a textual alternative language translation of a presentation's primary audio language that is usually burned-in (or "open") to the video and unselectable. HTML5 defines subtitles as a "transcription or translation of the dialogue ... when sound is available but not understood" by the viewer (for example, dialogue in a foreign language) and captions as a "transcription or translation of the dialogue, sound effects, relevant musical cues, and other relevant audio information ... when sound is unavailable or not clearly audible" (for example, when audio is muted or the viewer is deaf or hard of hearing).

The term "closed" (versus "open") indicates that the captions are not visible until activated by the viewer, usually via the remote control or menu option. On the other hand, "open", "burned-in", "baked on", or "hard-coded" captions are visible to all viewers.

Most of the world does not distinguish captions from subtitles. In the United States and Canada, however, these terms do have different meanings. "Subtitles" assume the viewer can hear but cannot understand the language or accent, or the speech is not entirely clear, so they transcribe only dialogue and some on-screen text. "Captions" aim to describe to the deaf and hard of hearing all significant audio content - spoken dialogue and non-speech information such as the identity of speakers and, occasionally, their manner of speaking - along with any significant music or sound effects using words or symbols. Also, the term closed caption has come to be used to also refer to the North American EIA-608 encoding that is used with NTSC-compatible video.

...
Wikipedia