Captions allow viewers who are deaf or hard of hearing to follow the dialogue and the action of a program simultaneously. They can also provide information about who is speaking or about sound effects that may be important to understanding a news story, a political event, or the plot of a program. Captions are created from the transcript of a program. A captioner separates the dialogue into captions and makes sure the words appear in sync with the audio they describe. A specially designed computer software program encodes the captioning information and combines it with the audio and video to create a new master tape.
Open captions appear on all television sets and can be viewed without a decoder.
With the widespread availability of closed-caption technology, open captions are rarely used. A computer translates the phonetic symbols into English captions almost instantaneously. The slight delay is based on the captioner's need to hear the word and on the computer processing time. Although most real-time captioning is 98 percent accurate, the audience will see occasional errors. The captioner may mishear a word, hear an unfamiliar word, or have an error in the software dictionary.