In conventional movie theaters, captions are fed to the LED panel by the DTS digital audio system. The caption data reside on a CD that plays alongside the other discs in the DTS player. A reader head attached to the film projector reads a timecode track printed on the film and signals the DTS player to play the audio and captions synchronous to the film. The DTS player in turn sends the captions to the LED display. In specialty theaters, caption data are fed to the LED panel by a computer that is running special software that synchronizes the caption files to the film.
Open captions are similar to subtitles.
To provide open captions, it is necessary for studios to create and for exhibitors to obtain a special print of the film. Open-captioned films are generally presented at special screenings. The Rear Window system is a way of providing closed captions. The captions are not on the film itself, so there is no need for a special print. The captions are on a floppy disk or CD that plays in synchronization with the film.