Laserdisc

The Laserdisc was an optical video disc medium released in 1978 in various countries, but mostly a failure except in Japan. Its laser-read technology was similar to what was later used in more-successful media including the CD and DVD.

Laserdiscs are larger than CDs or DVDs in physical size, but have a lower information density. Three encoding formats were used: CAV (Constant Angular Velocity or Standard Play), supporting 30 minutes of video per side; CLV (Constant Linear Velocity or Extended Play), supporting 60 minutes per side; and CAA (Constant Angular Acceleration), used in later discs. The discs were double-sided, with some players able to play both sides without manual flipping, and others requiring a turnover as with vinyl records.

Laserdiscs were used for computer games and karaoke discs as well as their primary use as a video medium.

A modified Laserdisc was used for the BBC Domesday Project in 1986 to store a collection of media regarding life in Britain at the time. This is regarded as an example of archival obsolescence due to the use of formats that are difficult to access in the present. The LV-ROM format was used for data storage, and it was designed to be used with an Acorn computer and a specialized disc drive with a Domesday-specific controller, none of which can easily be found now in order to attempt to access the few surviving copies of these discs. Stations with the required hardware are set up at a computing museum, and some parts of the project have been recovered and converted to other formats for web or PC use, but the work in its entirety remains very difficult to access and risks getting completely lost in the future. (See Wikipedia article and Domesday Reloaded website with a partial conversion.)

Links

 * Wikipedia article
 * Pioneer Announces End of LaserDisc Player Products
 * The Laserdisc FAQ
 * Laserdisc Database
 * How to rip a Laserdisc