Laserdisc

   

Laserdisc was the first optical disc storage medium, and was used primarily for the presentation of movies. During its development, the format was referred to as the "Optical Videodisc System" before MCA, who owned the patent on the technology, re-named the format "Discovision" in 1969. They marketed it under that name until "Laserdisc" began being used in the late 1980s by Pioneer Electronics. MCA also owned the rights to the largest catalog of films in the world at the time, and they directly manufactured and distributed the discs of their movies under the "MCA DiscoVision" label. In addition, they manufactured discs for other companies, including Paramount, Disney and Warner Brothers. Some of them added their own names onto the disc-jacket in order to signify that the movie was not owned by MCA. When MCA folded into Universal several years later, Universal began re-issuing many of the early DiscoVision titles as Universal discs. The DiscoVision versions had largely been avaliable only in pan and scan and had utilized poor transfers. The Universal versions were largely better. 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).

History

LD was invented by David Paul Gregg (died 2003) in 1958, patented in 1961 and 1969, 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.

Technical information

Video was stored on LD as an analog signal, while audio could be stored in either analog or digital format and in a variety of surround sound codecs. Like on a CD, the surface of the disc is an aluminium foil covered by pits and lands, but whereas on a audio CD (or DVD) the pits and lands will signify binary codes, on a LD the distance between two pits represents an analog sample level, the accuracy of which is dependent on the quality of the measurement.

NTSC discs could carry two analog audio tracks, plus two uncompressed PCM digital audio tracks, which were generally CD quality. PAL discs could carry one pair, either analog or digital. Dolby Digital (also called AC-3) and DTS, which are now common on DVD titles, first became avaliable on Laserdisc. Star Wars: Episode I (1999) was released on Laserdisc in Japan, and holds the distinguishing record of being both the first home video release to include 6.1 channel Dolby Digital EX Surround, and the only Laserdisc to ever include the EX codec. Many later discs forwent an analog audio track entirely, offering the choice of a CD-quality PCM audio track (carried directly via the player's optical output) or Dolby Digital, which could exceed CD sound quality. Players could generally down-convert PCM tracks using an internal digital to analog converter and output the sound in analog form via RCA connection. This allowed people who were not equipped with either Dolby Digital compatible hardware or a reciver with an optical audio input to watch those discs. DTS equipped discs would still be equipped with an analog channel, as DTS uses the space the PCM tracks would normally occupy.

Unlike DVDs, which carry Dolby Digital audio in unmodulated form on a dedicated track, Laserdiscs stored Dolby Digital in a frequency modulated form on a track normally used for analog audio. Extracting Dolby Digital from a Laserdisc required a player equipped with a special "AC-3 RF" output and an external demodulator in addition to an AC-3 decoder. The demodulator was neccesary to take the 2.88 MHz modulated AC-3 information off the disc via the RF output, and turn it into a 384 kbit/s signal that the decoder could understand. DTS audio took the place of the PCM audio tracks, and required only a direct connection via Optical Audio cable and a decoder to be heard.

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.

Many Laserdisc player manufactured from the late 1980s through the formats death had both composite (red, white and yellow RCA type connectors) and S-Video outputs on the rear panel. When using the S-Video connection, the player would utilize it's own internal comb filter, designed to help reduce picture noise, while using the composite outputs forced the player to rely on the comb filter of the display device, if so equipped. Although using the S-Video connection was often considered to yield superior results in the late 80s and early 1990s, most of today's mid and high level television sets contain better comb filters than what the vast majority of players were equipped with. In these instances, where a player is being used with a more modern display, using the composite output and allowing the display device's internal comb filter to do the work often yields the better results.

Laserdisc vs. VHS

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 such as director commentaries to be released, a practice initiated by the Criterion Collection, with their 1984 LD edition of Citizen Kane. 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. LDs would never "wear out" or lose quality with each playback as VHS tapes do.

The format was not without its disadvantages. The discs were 30cm (12 inch) across, and were both fragile and heavy. There was no way for home users 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 1990s.)

Laserdisc vs. DVD

It is interesting to note that the differences between LD technology and DVD have lead some videophiles to prefer LD. Laserdiscs use only analog video and always carry some form of analog audio. Many purists believe that analog media is capable of higher quality than digital A/V carriers such as CD and DVD. However, this is rarely achieved in practice. Only expertly mastered analog LDs may exhibit this superior quality and even then it requires very expensive high-end components (LD player, amplifier, television, etc.) in order to actually realize the benefits.

An advantage to the Laserdisc format over DVD is that video is not digitally-encoded and compressed, and therefore does not experience problems such as artifacting (most visible as blockiness during high motion sequences) or color banding (subtle visible lines in gradient areas, such as skies) that is inherent in the MPEG-2 encoding process as video is prepared for DVD. However, the meticulous (and expensive) frame-by-frame tuning of the lossy MPEG-2 encoding process coupled with the variable bit-rate technology generally employed on big-budget DVD releases effectively eliminates this, and an optional feature of the MPEG-2 compression standard allows much higher color resolution to eliminate the visible effect of color banding on some high-end home theatre equipment.

A disadvantage with the analog nature of Laserdiscs is that most players exhibit a slight but perceivable 30 Hz video flicker, and slight dust and wear on the hardware or disc can degrade video and audio over time. The DVD format, however, does not introduce any flicker, and the format's digital nature and sophisticated error-correction scheme can often produce spotless video/audio from a DVD, even with dust and scratches on the surface. Laserdisc players also suffered a problem known as "crosstalk". The issue came up when the wide wavelength laser inside the player accidentally picked up picture information from a track adjacent to where it was reading on a disc. The added information usually showed up as distortion in the picture. Some players were better at compensating for and/or avoiding crosstalk entirely than others.

Success of the format

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 decks and tapes. In Japan, the LD strategy was very similar to the strategy taken by DVD manufacturers early in it's life: prices were kept low to ensure adoption, resulting in minimal price differences between VHS tapes and the higher quality Laserdiscs. LD also quickly became the dominant format of choice amongst Japanese collectors of anime, helping drive its acceptance.

Nontheless, the Laserdisc format did not allow for recording onto the discs, while the competing video cassette recorder devices could record using tape cassettes. Combined with the cumbersome disc size and high North American prices for both players and media, the format was doomed to obscurity. 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 the Laserdisc format has been completely supplanted by DVD, and players are no longer manufactured outside Japan, 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. There are many films that are only available on LD. As well, there are various films for which the LD is the most desirable release due to extra scenes, superior mastering, or lack of DVD availability. Thus, many LDs are still very much in demand.

Examples include the anime Five Star Stories, which was only released on LD despite its extreme popularity. Enthusiasts have been known to pay $700 or more for this LD. Likewise, the LD releases of the original Star Wars trilogy are in high demand among fans as, out of all home video releases of the pre-'Special Edition' versions of the films, they offer the highest video and audio quality.

It should be noted that the popularity of the LD format in Japan is still great enough that Pioneer continues to manufacture and market two players. The first, the DVL-919 is a DVD/Laserdisc combination unit that was sold for a short while in the U.S. and was subsequently discontinued in 1999 when the format had lost the vast majority of it's waning support. The second, a Laserdisc-only player, model designation CLD-R5, is also manufactured and sold at a lower cost. Rumor has it that select Pioneer dealers still have access to left-over, North American specifcation DVL-919s but this should be taken with a grain of salt.

Certain Japanese players, which are considered to be of higher quality or of greater capacity for quality playback than the North American units are occasionally imported by enthusiasts. These include the CLD-R7G, LD-S9 and HLD-X9. All three are manufactured by Pioneer and all three contain technology that was never offcially avaliable in North America. In the case of the LD-S9 and CLD-R7G the added benefits mainly have to do with the internal comb filters the units utilize when operating via S-Video connection. The LD-S9 shares it's highly advanced comb filter with the HLD-X9, which was also a Muse LD player with a red-laser system.

Laserdisc variations

In 1991, several manufacturers announced specifications for what would become known as "MUSE" Laserdisc. Encoded using technology adopted from "Hi-Vision" (Japanese HDTV) hardware, MUSE discs would operate like standard Laserdiscs but would contain material transfered in High Definition (1080i) anamorphic widescreen. The MUSE players were also capable of playing standard NTSC format discs and are said to have superior performance to non-MUSE players. The MUSE-capable players had several noteworthy advantages over standard Laserdisc players, incuding a red laser with a much narrower wavelength than the lasers found in standard players. The red laser was capable of reading through disc defects such as scratches and even light disc-rot that would cause most other players to stop, stutter or drop-out. Crosstalk was not an issue with MUSE discs, and the narrow wavelength of the laser allowed for the virtual elimination of crosstalk with normal discs. In order to view MUSE encoded discs, it was neccesary to have a MUSE decoder in addition to a compatible player and an HDTV. Equipment prices were high, and even in Japan the market for MUSE was tiny. Players and discs were never offically sold in North America, although several distributors imported MUSE discs along with other import titles. Terminator 2, Lawrence of Arabia,A League of Their Own, Bugsy, Close Encounters of the Third Kind, Bram Stoker's Dracula and Chaplin were among the theatrical releases avalible on MUSE. Several documentaries, including one about race cars at Japan's Suzuka Circuit were also released.

Shortly before the format's death, a small number of discs were sold in Japan which contained an anamorphic image technology marketed as "squeeze", similar to the 16x9 anamorphic system used in DVDs. Among the very few films available in this format were Terminator 2, Basic Instinct, and The Fugitive. Unlike MUSE discs, Squeeze titles required a widescreen television set to display the squeezed image correctly, and they ran at standard resolution, around 480i. Widescreen sets cost considerably more than a standard set at the time, and as a result the format never caught on.

There are also "LD singles" which are 18 cm (7" aprox. , the same size as a 45-RPM record) across rather than the full 30 cm (12" aprox.) size. LD singles only contained a few minuites of video, enough for a music video or two. They are much rarer than the full-size LDs, especially in North America.

Some laser discs, called "picture discs", have artistic etching on one side of the disc to make the disc more visually attractive than the standard shiny silver surface. This etching might look like a movie character, logo, or other promotional material. Sometimes that side of the LD would be made with colored plastic rather than the clear material used for the data side. Picture disc LDs only had video material on one side as the "picture" side could not contain any data. Picture discs are rare in North America.

Pioneer Electronics, one of the format's largest supporters/investors, was also deeply involved in the karaoke business in Japan, and used laserdiscs as the storage medium for music and additional content such as graphics. The format was generally called LD+G. While several other karaoke labels did manufacture laserdiscs, there was nothing like the breadth of competition in that industry that exists now, as almost all manufacturers have transitioned to CD+G discs (enroute, possible, to a new DVD based format).

There existed another type of video media, CRV Disc, or "Component Recordable Video Disc". CRV discs resemble early PC CD-ROM caddies. The plastic housing of a CRV disc encloses an optical disc that resembles a standard LD. CRV discs existed as both pre-recorded releases and also as blank media that could be recorded, much like CD-R media. CRV was rarely used by the consumer due to the high cost of the equipment and media.

External links

de:Laserdisk fr:Laserdisc ja:レーザーディスク


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