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Laserdisc, LD, or video laser disc was the first optical disc storage media, and an industry-wide term for consumer laser video. During its life, the format has also been known as LV (for LaserVision, actually a player brand by Philips). The players are also sometimes referred to as VDPs (Video Disc Players). Before release it was promoted under the name "Discovision".

LD was invented by Philips in the late 1960s and first demonstrated by Philips and MCA in 1972. It was available on the market in 1978, or about the same time as the VCR and six years earlier than the CD. There are more than 1 million players in home use in the US (compared to 85 million VCRs), and more than 4 million in Japan (ten percent of households there). LD has been largely replaced by DVD.

Video was stored on LD as an analog signal, while audio could be stored in a combination of several different formats. NTSC LDs carried two analog audio tracks, plus two uncompressed CD-quality PCM digital audio tracks. PAL discs could carry one pair, either analog or digital. Some later LDs featured 5.1 channel Dolby Digital in place of the right analog audio track, and a small number included 5.1 channel DTS in place of the standard digital tracks.

Laserdiscs were recorded in one of two formats: CAV (constant angular velocity) or CLV (constant linear velocity). CAV discs were spun at a constant rotational speed during playback, with one video frame read per revolution, whereas CLV discs spun progressively slower as the disc was played from inside edge to outside edge. CAV could hold up to 30 minutes of content per side, while CLV could hold twice that. The advantage of the CAV format was that its simpler playback method allowed "trick play" features such as freeze frame, slow motion, and reverse on all LD players, unlike CLV which only supported those features on high-end models with digital video buffers. The vast majority of titles were only available in CLV.

LD had a number of advantages over VHS. It featured a far sharper picture and level of sound quality, with the ability to deliver multiple audio channels, both analog and digital. This allowed "special editions" of movies with extras like director commentaries to be released. Access was random, meaning that one could go to any point on the disc very quickly (depending on the player and the disc, within a few seconds at the most). This instant seeking allowed a new breed of laserdisc-based video arcade games, beginning with Dragon's Lair, to be born. As LDs were read optically instead of magnetically, a properly-manufactured LD would theoretically last beyond one's lifetime, and as the discs had no moving parts, they were cheaper to manufacture.

The format was not without its disadvantages. The discs were 12 inches across, and were both fragile and heavy. There was no way for home user to record to an LD. Depending on the format, each side of an LD could hold at most 30 or 60 minutes of content, and then the disc would have to be turned over. Most players did this automatically by rotating the optical pickup to the other side of the disc, but except in high-end models with a pre-read buffer, this was accompanied by a pause in the movie of around 10 seconds, and if the movie was longer than two hours, it eventually required putting in a second disc.

Many early laserdiscs were not manufactured properly. Sometimes a substandard adhesive was used to sandwich together the two sides of the disc, causing the disc to delaminate slightly and allowing oxygen to cause the metallic part of the discs to oxidize. This eventually destroyed the disc, a process known as "laser-rot" among LD enthusiasts. (Early CDs suffered similar problems, including a notorious batch of defective discs manufactured by Philips-DuPont Optical in Europe during the early Nineties.)

The format was not well-accepted outside of videophile circles in North America, but became more popular in Japan. Part of the reason was marketing. In North America the cost of the players and discs were kept far higher than VHS to make up for lack of demand. In Japan, LD was marketed like DVD (LD's replacement) was on its release—prices were kept low to ensure adoption, so in Japan an LD and a VHS tape were often identically priced. LD quickly became the dominant format-of-choice amongst Japanese collectors of anime, helping drive its acceptance.

A very small number of LDs were mastered, exclusively in Japan, using an anamorphic image technology, similar to the 16x9 anamorphic system used in DVDs. Among the very few films available in this format were Terminator 2, Basic Instinct and Luc Besson's Atlantis. Displaying the squeezed image correctly required a widescreen television set, which at the time cost considerably more than a standard set, and as a result the format never caught on.

The compact disc for audio was based on the laser disc technology. One reason for the (mostly) failure of laser discs may have been that it was not possible to record them, and the competing video cassette recorder devices could record using tape cassettes. When they were first introduced, laser discs were believed to be disruptive technology, a promise they failed to fulfill. Compact discs and DVDs were to be disruptive instead.

Although LDs and their players have been completely supplanted by DVD and are no longer manufactured, many LDs were considered definitive releases of movies and are still highly coveted by movie enthusiasts. Boxed multi-disc LD editions of several films are prized as collector's items.

External link

• The Laserdisc FAQ