videodisc or videodisk, disk used with a special player and television to reproduce both pictures and sound. A videodisc player cannot record television programs off the air for later playback, unlike a videocassette recorder (VCR) or recordable DVD (see digital versatile disc). Videodiscs generally produce pictures that are clearer in detail and truer in color than those produced by VCR tapes, and they also offer better sound quality, but the introduction of the DVD led to their becoming obsolete. Two quite different videodisc systems were developed. One operates much like a record player, using a mechanical stylus that senses varying patterns of electrical capacitance imprinted in grooves on the disc surface. That format fell into disuse, becoming superseded by the laser disc system, which uses a laser to read a track cut in a spiral pattern on the inside surface of the disc. On a laser disc, video is recorded as an analog signal and the soundtrack is either an analog or, in later versions, a digital signal.

Rigid circular plate of either metal or plastic used to record video and audio signals for playback. It resembles a phonograph record and can be played on a machine attached to a conventional television receiver. There are two major classes of videodiscs, magnetic and nonmagnetic. Magnetic videodiscs have an oxide-coated surface onto which input signals are recorded as magnetic patterns in spiral tracks. Nonmagnetic videodiscs use either a mechanical recording system analogous to that used in phonograph records, or optical technology that uses a laser to read data coded as a sequence of pits on the disc. The most common type of videodisc today is the DVD.

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