LaserDisc (LD) is a home video format and the first commercial optical disc storage medium. It was developed by Philips, Pioneer, and the movie studio MCA, and was initially licensed, sold, and marketed as DiscoVision in the United States in 1978. The discs typically have a diameter of , similar in size to the phonograph record. Unlike most later optical disc formats, LaserDisc is not fully digital; it stores analog video signals.