Prerecorded Programs
Several systems work together in order to create closed captioning subtitles for television programming. Whoever is responsible for distributing the program (cable operators, satellite operators or broadcasters) must transcribe the audio of each distributed show. Then another group in the distribution team takes the transcription and prepares each line of the closed captioning subtitles. This task requires lining up the captions at the correct time in the video playback.
Live Television
Most broadcasters of live programs use an automatic transcription system to create closed captioning. The audio feed of the live television show is played on a computer, which then uses a speech-to-text program to transcribe it. The audio input is automatically translated into text by the computer, displayed on the screen and then sent out to viewers by the broadcasters. Because of the time it takes the computer to translate the audio, closed captioning on live programs often falls behind by a few seconds.
Caption Viewing
All modern televisions are required by the FCC to have a closed captioning function. When viewers activate this option, the embedded audio transcript of the current program begins to appear on the screen. Closed captioning subtitles are displayed on televisions by encoding the text onto an outer interval of the picture so that the lines of subtitles lie just above the normal picture. Closed captioning options and preferences are usually configured through a television's remote control.
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