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SelectaVision

From Academic Kids

SelectaVision was originally the name for a video playback system developed by RCA using specialized disc-based media, in which video and audio could be played back on a TV using a special analog needle and groove system similar to phonograph records.

The format was commonly known as "videodisc", leading to much confusion with Laserdisc format, which is mutually incompatible with this format.

The name "SelectaVision" was also used for some early RCA brand VCRs.

Contents

Development and Lifespan

It was first developed in the 70’s by RCA and first sold in 1981 in the United States and Canada. It was discontinued in 1984.

How SelectaVision Worked

SelectaVision used a special medium known as a Capacitance Electronic Disc (CED). The VideoDisc was a 12 in (305 mm) platter housed in a special caddy. The video and audio signal is stored on the Videodiscs via hills and valleys etched in grooves on both sides of the discs much like a phonograph record. To play a Videodisc, you inserted the caddy into the player and the platter would be extracted. A needle would read the video and audio signals from the grooves.

Unlike a phonograph record, where physical movement (vibration) of the stylus in the groove of the platter led to an audio signal, the stylus in a SelectaVision player slid along the crests of the groove, at a platter speed of 450 rpm. The varying thickness of the groove layer provided differing amount of capacitance between the stylus and a nickel subtrate within the platter (hence the technical term Capacitance Electronic Disc). This varying capacitance was measured by the player circuitry, providing an audio/video signal.

Also unlike a phonograph record (and more like a floppy disk), the grooves on a CED did not consist of a single groove in a spiral, but of concentric grooves, each containing a fixed amount of audio/video time (8 interlaced video frames, or 4 complete video frames—1/15 of a second).

The platter is stored inside the case, aka sleeve or caddy, which is lined on the inside with cotton fabric. The platter itself is surrounded by the "spine", a plastic ring (actually squarish on the outside edge) with a thick, straight rimlike edge, which extends outside of and latches into the caddy, serving as a cover. When the disc is inserted into the player, both the platter and the spine are contained inside.

Features of SelectaVision

Like VCR’s, SelectaVision Videodisc Players had features like rapid forward/reverse and visual search forward/reverse as well as a pause feature. Since they were a disc based system unlike the tape system of VHS and Beta VCR’s, they did not require rewinding. Early discs were generally monaural but later discs included stereo sound. Other discs could be switched between two separate mono audio tracks, providing features such as bilingual audio capability.

Each side of a CED disc could be split into up to 63 "chapters", or bands, which on some later players could be accessed directly. Novelty discs and CED-based games were produced whereby accessing the chapters in a specified order would string together a different story each time.

Disadvantages of SelectaVision

In comparison to VCR technology, CEDs suffered a few disadvantages. Most significantly, nearly all CED players (save some very late models) could only play one side of the disc at a time, which was limited to about 60 minutes of video. In order to play the entirety of a video recording longer than 60 minutes, the disc would have to be manually turned over. Due to the sensitive nature of the discs, the platters themselves were never meant to be exposed to open air outside of a player. In order to flip a CED disc, the disc's sleeve would be inserted into the player to enclose and store the platter, and the sleeve would then be removed (with platter now inside), flipped over, and reinserted into the player (which would again extract the platter, now with the reverse side facing the stylus). Movies longer than 2 hours would require a second disc, which would need to be swapped in the player with the first disc after the 2 hour mark.

Due to the discs' sensitivity, and the unavoidable friction between the stylus and the platter, repeated playing could lead to degradation of the video signal. Furthermore, any particulates that found their way into the player, the disc sleeve, or any indelicate use of the sleeve to insert or extract the platter from the player could result in scratches or other interference to the platter, which often resulted in rapid "skipping" of the audio/video signal, as well as serious signal degradation. Through ideal conditions and use, RCA suggested that a CED had a quality lifespan of about 500 plays, but this does not take into account the many factors that can impact disc life.

Milestones

The first movie distributed in letterbox widescreen format, Amarcord, was released on SelectaVision in 1984.

See also

References

  • Cowie, Jefferson R. Capital Moves: RCA's Seventy-Year Quest for Cheap Labor. Ithaca, N.Y.: Cornell University Press, 1999. ISBN 0801435250.
  • Daynes, Rob and Beverly Butler. The VideoDisc Book: A Guide and Directory. New York: John Wiley and Sons, 1984. ISBN 0471803421.
  • DeBloois, Michael L., ed. VideoDisc/Microcomputer Courseware Design. Englewood Cliffs, N.J.: Educational Technology Publications, 1982. ISBN 0877781834.
  • Floyd, Steve, and Beth Floyd, eds. The Handbook of Interactive Video. White Plains, NY: Knowledge Industry Publications. 1982. ISBN 0867290196.
  • Graham, Margaret B.W. RCA and the VideoDisc: The Business of Research. (Also as: The Business of Research: RCA and the VideoDisc.) Cambridge: Cambridge University Press, 1986. ISBN 0521322820, ISBN 0521368219.
  • Haynes, George R. Opening Minds: The Evolution of Videodiscs & Interactive Learning. Dubuque, Iowa: Kendall/Hunt Publishing Co., 1989. ISBN 0840351917.
  • Isailovi´c, Jordan. VideoDisc and Optical Memory Systems. Englewood Cliffs, N.J.: Prentice-Hall, 1985. ISBN 0139420533.
  • Lardner, James. Fast Forward: Hollywood, the Japanese, and the VCR Wars. (Also as: Fast Forward: Hollywood, the Japanese, and the Onslaught of the VCR.) New York: W. W. Norton & Co Inc., 1987. ISBN 0393023893.
  • Lenk, John D. Complete Guide to Laser/VideoDisc Player Troubleshooting and Repair. Englewood Cliffs, N.J.: Prentice-Hall, 1985. ISBN 0131608134.
  • Schneider, Edward W., and Junius L. Brennion. The Instructional Media Library: VideoDiscs, (Volume 16). Englewood Cliffs, NJ: Educational Technology Publications. ISBN 0877781761. 1981.
  • Sigel, Efrem, Mark Schubin and Paul F. Merrill. Video Discs: The Technology, the Applications and the Future. White Plains, N.Y. : Knowledge Industry Publications, 1980. ISBN 0914236563. ISBN 0442277849.
  • Sobel, Robert. RCA. New York: Stein and Day/Publishers, 1986. ISBN 0812830849.
  • Sonnenfeldt, Richard. Mehr als ein Leben (More than One Life). ?, 2003. ISBN 3502186804. (In German.)
  • Journals:
    • The Videodisc Monitor
    • Videodisc News
    • Videodisc/Optical Disk Magazine
    • Video Computing

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