closed captioning

n.A transcription of a television program audio track encoded in the signal that allows hearing-impaired viewers to read dialog as subtitles or on a special decoder.


The transcription generally captures only spoken language, but may use symbols or description to indicate other sounds necessary to understand the program. For example, the sound of a car off-camera driving away may be described as 'car leaving.' The closed-caption signal is encoded on line 21 of an National Television Systems Committee (NTSC) signal. Closed captioning is limited to video programs. It is distinguished from subtitles, which are captions in movies, and captioning in other settings, such as opera or theatrical productions.