Disc Formats | LaserDisc (LD)

During its development, the format was referred to as the 'Reflective Optical Videodisc System' before MCA, who owned the patent on the technology, renamed the format Disco-Vision in 1969. By the time the format was brought to market in 1978, the hyphen had been removed from the format name, and DiscoVision became the official name. Sales of DiscoVision players & discs began on December 15, 1978 starting in Atlanta, Georgia. MCA owned the rights to the largest catalog of films in the world during this time, and they directly manufactured and distributed the discs of their movies under the 'MCA DiscoVision' label. Pioneer Electronics, who entered the market at almost exactly the time DiscoVision titles were going on sale in 1978, began manufacturing players and printing discs under the name Laser Videodisc. By 1981, Laserdisc (first in CamelCase as LaserDisc, later without the intercap) had become the common name for the format, and the DiscoVision label disappeared, becoming simply MCA or (later) MCA-Universal Laserdisc.

MCA also 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 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 available only in pan and scan and had often utilized poor transfers. 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

Laserdisc technology, using a transparent disc, was invented by David Paul Gregg in 1958 (and patented in 1961 and 1969). By 1969 Philips had developed a videodisc in reflective mode, which has great advantages over the transparent mode. MCA and Philips decided to join their efforts. They first publicly demonstrated the videodisc in 1972. It was first available on the market, in Atlanta, on December 15, 1978, two years after the VHS VCR and five years before the CD, which is based on laserdisc technology. Philips produced the players and MCA the discs. The Philips/MCA cooperation was not successful, and discontinued after a few years.

There are more than 1 million players in home use in the U.S. (compared to 85 million VCRs), and more than 4 million in Japan (or 10% of households). LD has been completely replaced by DVD in the North American retail marketplace, as neither players nor software are now produced there. Laserdisc has retained some popularity among American collectors and to a greater degree, in Japan, where the format was better supported and more prevalent during its life. In Europe, on the other hand, LD has always remained an extremely obscure format.

Resembling a large audio Compact Disc, the standard movie laserdisc was 30 cm in diameter and made up of two single-sided stamped aluminum discs bonded with glue and sandwiched between two sheets of plastic. Laserdisc is an analog format, unlike the modern CD or DVD which are digital formats. Both formats are pressed with pits and lands making up the structure of the disc. On a digital audio CD (or DVD) the pits and lands will signify binary codes; with a Laserdisc, the pits and lands are created using frequency modulation of an analog signal, with the frequency carrier encoded using pulse-width modulation. Additionally, all laserdiscs could be encoded with chapters akin to tracks and display several modes of time, such as 'elapsed', 'left in chapter', and 'left in side'.

Audio

Audio could be stored in either analog or digital format and in a variety of surround sound formats; NTSC discs could carry two analog audio tracks, plus two uncompressed PCM digital audio tracks, which were CD quality (2 channels, 16 bit, 44.1KHz sample rate for PAL and 44056Hz for NTSC, and a 96dB signal-to-noise ratio). PAL discs could carry one pair of audio tracks, either analog or digital; in the UK the term LaserVision is used to refer to discs with analog sound, while LaserDisc is used for those with digital audio. Dolby Digital (also called AC-3) and DTS, which are now common on DVD titles, first became available on Laserdisc, and Star Wars: Episode I (1999) which was released on Laserdisc in Japan, is among the first home video releases ever to include 6.1 channel Dolby Digital EX Surround. Unlike DVDs, which carry Dolby Digital audio in digital form, Laserdiscs store Dolby Digital in a frequency modulated form within 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 necessary to convert the 2.88 MHz modulated AC-3 information on the disc into a 384 kbit/s signal that the decoder could handle. DTS audio, when available on a disc, replaced the digital audio tracks; hearing DTS sound required only an optical digital audio connection to a DTS decoder.

At least where the digital audio tracks were concerned, the sound quality was unsurpassed at the time, but the quality of the analog soundtracks varied greatly depending on the disc and, sometimes, the player. Many early and lower-end LD players had poor analog audio sections, and many early discs had poor analog audio tracks, making digital soundtracks in any form most desirable to serious enthusiasts. Early Discovision and Laserdisc titles lacked the digital audio option, but many of those movies received digital sound in later re-issues by Universal, and the quality of analog audio tracks generally got better as time went on. Many discs that had originally carried old analog stereo tracks received new Dolby Stereo and Dolby Surround tracks instead, often in addition to digital tracks, helping boost sound quality. Later discs also applied CX Noise Reduction, which improved the signal-noise ratio of analog audio. In addition many later PAL discs have no analog audio track at all, instead offering the choice of the PCM digital audio track or Dolby Digital.

Both AC-3 and DTS surround audio were clumsily implemented on laserdiscs, leading to some interesting player- and disc-dependent issues. A disc that included AC-3 audio forfeited the right analog channel to the modulated AC-3 stream. If the player did not have an AC-3 decoder available, the next most attractive option would be the stereo digital tracks. If either the player did not support digital tracks or the disc did not include digital tracks, the only remaining option was to fall back to a monophonic presentation on the analog left track. However, a player that is not aware of AC-3 streams (independent of its ability to decode them) will play the analog audio tracks verbatim, resulting in garbage output in the right channel. With a DTS disc, the PCM digital tracks are not available, so if a DTS decoder was also not available, the only option was to fall back to the stereo analog tracks.

Usually, only one surround sound option existed on a given laserdisc (Dolby Surround, Dolby Digital, or DTS), so if surround sound is desired, the disc must be carefully matched to the player's capabilities by the purchaser. It should also be noted that both the analog and digital tracks are capable of carrying Dolby Surround-encoded information (whether a particular disc does depends on the manufacturer), and that given a Dolby Surround-encoded source, Laserdisc players and surround-sound processors that implement Dolby Pro Logic are capable of surround output superior to those which only decode Dolby Surround.

CAV (Constant Angular Velocity) or Standard Play discs supported the several unique features such as freeze frame, variable slow motion and reverse. CAV discs were spun at a constant rotational speed during playback, with one video frame read per revolution and in this mode, 54,000 individual frames or 30 minutes of audio/video could be stored on a single side of a CAV disc. Another unique attribute to CAV was to reduce the visibility of cross talk from adjacent tracks, since on CAV discs any crosstalk at a specific point in a frame is simply from the same point in the next or previous frame. CAV was used less frequently than CLV, reserved for special editions of feature films to highlight bonus material and special effects.

CLV (Constant Linear Velocity) or Extended Play discs do not have the 'trick play' features of CAV, offering only simple playback on all but the high-end laserdisc players incorporating a digital frame store. These high-end laserdisc players could add features not normally available to CLV discs such as variable forward and reverse, and a VCR-like 'pause'. CLV encoded discs could store 60 minutes of audio/video. The vast majority of titles were only available in CLV.

CAA (Constant Angular Acceleration). In the early 1980s, due to problems with crosstalk distortion on CLV extended play LaserDiscs, Pioneer Video introduced CAA formatting for extended play discs. Constant Angular Acceleration is very similar to Constant Linear Velocity save for the fact that CAA varies the angular rotation of the disc in controlled steps instead of gradually slowing down as a CLV disc is read. With exception to 3M/Imation, all LaserDisc manufacturers adopted the CAA encoding scheme, even though many manufacturers still referred CAA extended play discs ubiquitously as CLV on the disc packaging.

Many Laserdisc players manufactured from the late 1980s through the time of the format's 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 its own internal comb filter, designed to help reduce picture noise by separating the luminance (brightness) and color parts of the signal, while using the composite outputs forced the player to rely on the comb filter of the display device. 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 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 better results.

In 1996, the first model DVD/LD combi-player and first Pioneer DVD player for that matter was the Pioneer DVL-9 released in Japan. The Pioneer Elite DVL-90 an updated version, followed by a similar, though supposedly lower-end model, the DVL-700, and were released in 1997. Successors to this model include the Pioneer DVL-909, Pioneer DVL-919, and the Pioneer Elite DVL-91. Although the DVD/LD combi players offered competent LD performance, they paled in comparison to high end LD players such as the Pioneer Elite CLD-99 and the Pioneer Hi-Vision/MUSE HLD-X9.

The last model DVD/LD player, the DVL-919, is still sold in the U.S. and appears on Pioneer's North American website. However, it has not been actively marketed since the late 1990s. The DVL-919 supports DTS output. The DVL-919's DVD section is unremarkable by modern standards, and does not support progressive scan (480p) even though it has component output. As noted above, the LD section, while competant, is inferior to earlier high end LD players. A few Pioneer dealers offer North American specification DVL-919s, and a unit purchased in April 2004 had a manufacture date of December 2003. Pioneer representatives reportedly state that the product is officially discontinued, and that warranty coverage for 919s will be based on the date of manufacture rather than on the date of sale.

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, HLD-X9 and HLD-X0. All Four are manufactured by Pioneer and all three contain technology that was never officially available in North American Laserdisc players. The CLD-R7G, LD-S9 and HLD-X9 share a highly advanced comb filter, allowing them to offer a considerable advantage in picture quality over most other LD players when the S-Video connection is used. The comb filter present in these players is unique and is purportedly the finest comb filter ever used in consumer A/V gear, it is still currently in use in Mitsubishi's top-spec CRT rear projection television sets (the Diamond and now defunct Platinum series sets) and Pioneer's Elite line of rear projection televisions. In addition to the advanced comb filter, the HLD-X9 contains a red laser pickup which significantly reduces crosstalk and picture-noise levels compared to players with the traditional infrared laser; it can also read through all but the worst cases of laser rot and surface wear. The HLD-X9 is, lastly, also a MUSE player, capable when properly equipped of playing back high definition laserdiscs, called Hi-Vision or MUSE discs in Japan. The HLD-X0 is Pioneer's original MUSE player, and is the player of choice for many enthusiasts despite the fact that it lacks the comb filter shared by the R7G, S9 and X9. It was entirely hand built from hand picked electronics and weighed a massive 36 kilograms. Many argue that the newer X9 was a more capable MUSE player but that the X0 had superior performance with standard NTSC discs. Nonetheless, the X9 remains the more popular of the two models, as it includes the newer comb filter and is a dual-side player, meaning that double sided discs don't need to be manually flipped over in order for both sides to be played.

LD had a number of advantages over VHS. It featured a far sharper picture with a horizontal resolution of 400 lines for NTSC and 440 lines for PAL discs, while VHS only featured 240 lines. It could handle analog and digital audio where VHS was analog only, and the NTSC discs could store multiple audio tracks. This allowed for extras like director's commentary tracks and other features to be added on to a film, creating 'Special Edition' releases that would not have been possible with VHS. Disc access was random and chapter based, like the DVD format, meaning that one could jump to any point on a given disc very quickly (depending on the player and the disc, within a few seconds at the most). By comparison, VHS would require tedious rewinding and fast-forwarding to get to specific points. Laserdiscs were cheaper than videocassettes to manufacture, because they lack the moving parts and plastic outer shell that are necessary for VHS tapes to work. (A standard VHS cassette has at least 14 parts including the actual tape. A Laserdisc has one part, with five or six layers.)

Moreover, because the discs are read optically instead of magnetically, no physical contact needs to be made between the player and the disc, except for the player's clamp that holds the disc at its center as it is spun and read. As a result, playback does not wear the information-bearing part of the discs, and properly manufactured LDs will theoretically last beyond one's lifetime. By contrast, a VHS tape holds all of its picture and sound information on the tape in a magnetic coating which rubs directly against the player heads, causing progressive wear with each use. Also, the tape is thin and delicate, and it is easy for a player mechanism (especially on a low quality model) to mishandle the tape and damage it by creasing it, frilling (stretching) its edges, or even breaking it.

The format's support for multiple audio tracks allowed for vast supplemental materials to be included on-disc and made it the first viable format for 'Special Edition' releases; the 1984 Criterion Collection edition of Citizen Kane is generally credited as being the first 'Special Edition' release to home video, and for setting the standard by which future SE discs were measured. In addition, the format's instant seeking capability made it possible for a new breed of laserdisc-based video arcade games, beginning with Dragon's Lair, to be born.

And despite their large physical size, the space-consuming analog video signal of a LaserDisc limited playback duration to 30 or 60 minutes per side. After one side was finished playing, a disc would have to be flipped over in order to continue watching the film, and many films required two discs or more. Many players, especially units built after the mid-1980s, could 'flip' discs automatically by rotating the optical pickup to the other side of the disc, but this was accompanied by a pause in the movie during the side change. If the movie was longer than what could be stored on 2 sides of a single disc, manually swapping to a second disc would be necessary at some point during the film.

To make matters worse, many early LDs were not manufactured properly; sometimes a substandard adhesive was used to sandwich together the two sides of the disc. The adhesive contained impurities that were able to penetrate the lacquer seal layer and chemically attack the reflective substrate, causing it to oxidize and lose its reflective characteristics. This was a problem that was coined 'laser rot' (or, 'LaserRot', after the original official CamelCase 'LaserDisc' name of the underlying product) 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.

The differences between LD technology and DVD have led some videophiles to prefer LD. Laserdiscs use only analog video and almost always carry some form of analog audio. Some claim that analog media are capable of higher quality than digital A/V carriers such as CD and DVD, and early DVD demo discs often had compression or encoding problems, giving LD proponents fuel for the fire. However, 'LD-perfection' is rarely achieved in practice. Only the absolute best LDs, few and far between, exhibit such superior quality in comparison to the newer DVDs, and even then, expensive equipment is required to 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 macroblocking (most visible as blockiness during high motion sequences) or contrast banding (subtle visible lines in gradient areas, such as skies or light casts from spotlights) that can be caused by the MPEG-2 encoding process as video is prepared for DVD. Fortunately, however, the meticulous frame-by-frame tuning of the 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. Some videophiles will continue to argue that Laserdisc maintains a 'smoother' more 'film-like' image while DVD still looks slightly more artificial.

A disadvantage with the analog nature of Laserdiscs is that most players exhibit a slight but perceivable 25 or 30 Hz video flicker. Slight dust and scratches could cause various problems that could affect video quality and possibly also tracking accuracy of the disc by the player. Wearout and/or calibration drift on the hardware could also play a role in degrading video quality, audio quality, and tracking accuracy. The DVD format, however, does not introduce any flicker if played on progressive scan equipment, 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 to a certain extent.

Laserdisc players sometimes suffered a problem known as 'crosstalk' on extended play discs, usually with equipment requiring service of the laser optical pickup assembly when this occurs. However, the problem with crosstalk may also occur with poorly manufactured CLV Laserdiscs or with discs that are excessively warped. The issue came up when the optical pickup inside the player accidentally picked up the encoded video information from a track adjacent to where it was reading on the disc. The added information usually showed up as distortion in the picture, usually looking reminiscent of and referred to as 'barber poles'. Some players were better at compensating for and/or avoiding crosstalk entirely than others, provided that the cause of crosstalk was the disc and not the player. However, there is no crosstalk distortion on CAV standard play LaserDiscs as the rotational speed never varies. But, if the player calibration is out of order or if the CAV disc is faulty, other problems affecting tracking accuracy could occur, such as 'laser lock', a problem where the player reads the same track and, thus, the same two fields for one frame over and over again, causing the picture to freeze as if in pause.

Laserdisc is a composite video format: the luminance (black and white) and chrominance (color) information are transmitted in one signal and it is the responsibility of the receiver to separate them. While good comb filters can do a decent job at it, these two signals cannot be completely separated. On DVDs the signals are stored separately, which results in higher fidelity particularly at strong color borders or places with lots of detail, particularly if there is moderate movement in the picture. However, this also applies to low-contrast details like skin tones, where comb filters almost inevitably smudge some detail.

Another major advantage to DVD over Laserdisc was the fact that LD playback quality was highly dependent on player quality (as with any analog format). On most television sets, a given DVD player will produce a picture that is visually indistinguishable from other units; quality differences between players only become easily apparent with higher-end equipment. This was not true of Laserdisc playback quality. Major variances in picture quality could appear between different makes and models of LD player, even when tested on a TV that was not particularly high-end. This fact has had long lasting ramifications, as the pricing for what were considered to be good players has remained comparably high (anywhere from $200 to well over $1,000), while older and less desirable players can be purchased in working condition for as little as $25.

The format was not well-received 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 was kept far higher than VHS decks and tapes (mainly to combat anticipated losses at the box office). In Japan, the LD strategy was very similar to the strategy taken by DVD manufacturers early in its 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 to drive its acceptance. Also in Hong Kong, although the retail prices of laserdiscs were relatively high, they became quite popular in the city during the 1990s before the introduction of VCDs and DVDs. The reason was people rarely bought the discs; they usually rented them and the video renting business grew larger than ever at that time.

Nonetheless, 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 inconvenient disc size and high North American prices for both players and media, the format was doomed to obscurity. When they were first introduced, LaserDiscs were believed to be what would later be referred to as 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 new players are no longer sold outside Japan, many LDs are still highly coveted by movie enthusiasts. This is largely because there are many films that are still only available on LD and many other LD releases contain supplemental material not available on subsequent DVD versions of those films. As well, there are various films which are available on DVD as well as LD, but the LD version is preferred.

The most notable example is the Criterion Collection release of Blade Runner, as it is the highest-quality release of BR to contain a widescreen transfer of the theatrical cut of the film, whereas other releases have been only in pan and scan or of the 1992 'Director's Cut'. Other examples include the LD release of the anime To-y, which fetched as much as $700 from enthusiasts, and Five Star Stories, which fetched as much as $400 prior to its long-awaited release on DVD. This LD-only widescreen experience even applies to children's classics, like the Reader's Digest-produced 1970s musical versions of Tom Sawyer and Huckleberry Finn, which are only available in pan-and-scan versions on VHS and have yet to be released on DVD.

LD players are also sometimes found in contemporary North American high school and college physics classrooms, in order to play a disc of the Physics: Cinema Classics series of mid-20th century Encyclop�dia Britannica films reproducing classic experiments in the field which are difficult or impossible to replicate in the laboratories in educational settings.[2] These films have yet to be released on DVD.

Early in the eighties, Philips produced a laservision player model adapted for a computer interface, dubbed 'professional'. When hooked to a PC this combination could be used to display images or information for educational or archival purposes, for example thousands of scanned medieval manuscripts. This strange device could be considered a very early equivalent of a CD-ROM. In one case such a 'laserdisc-ROM' was still present, although rarely used, in 2001. A LaserDisc player attached to a BBC Master computer was used for the BBC Domesday Project.

In 1991, several manufacturers announced specifications for what would become known as MUSE Laserdisc. Encoded using NHK's MUSE 'Hi-Vision' analogue TV system, MUSE discs would operate like standard Laserdiscs but would contain high-definition 1125-line (1035 visible lines) video with a 5:3 aspect ratio. 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, including 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 mild 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 necessary to have a MUSE decoder in addition to a compatible player and a MUSE-compatible TV set. Equipment prices were high, especially for early HDTVs which generally eclipsed $10,000 USD, and even in Japan the market for MUSE was tiny. Players and discs were never officially sold in North America, although several distributors imported MUSE discs along with other import titles. Terminator 2: Judgment Day, 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 available on MUSE LDs. Several documentaries, including one about Formula One at Japan's Suzuka Circuit were also released.

There were also 12cm (5 inch, same as an audio CD) 'single'-style discs produced that were playable on laserdisc players. These were referred to as CD Video (CD-V) discs, and Video Single Discs (VSD). A CD-V carried up to 5 minutes of analog laserdisc-type video content (usually a music video), as well as up to 20 minutes of digital audio CD tracks. CD-Vs are not to be confused with Video CDs (which are all-digital and can only be played on VCD players, DVD players, CD-i players, computers, and later-model laserdisc players (such as the DVL series from Pioneer that can also play DVDs). CD-Vs can only be played back on laserdisc players with CD-V capability. VSDs were the same as CD-Vs, but without the audio CD tracks. CD-Vs were somewhat popular for a brief time worldwide, but soon faded from view. VSDs were popular only in Japan and other parts of Asia, and were never really introduced to the rest of the world.

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 manufactured 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 (en route, possibly, to a new DVD-based format).

Squeeze LD

With the release of 16:9 televisions in the mid 1990s, Pioneer and Toshiba decided that it was time take advantage of this aspect ratio. Squeeze LDs are enhanced 16:9 ratio widescreen Laserdiscs. In the video transfer stage the movie is stored in an anamorphic format. The widescreen movie image was stretched to fill the entire video frame with less or none of the video resolution wasted to create letterbox bars. The advantage was a 33% greater vertical resolution compared to regular Laserdisc. This similar procedure was used on DVD. Unlike DVD players very few LD players had the ability to unsqueeze the image. So if the disc were played on a 4:3 television the image would be distorted. Since very few people owned 16:9 displays, the marketability of these special discs was very limited.

There were no titles available in the US except for promotional purposes. Upon purchase of a Toshiba 16:9 television you have the option of selecting a number of Warner Brothers 16:9 films. Titles include Unforgiven, Grumpy Old Men, The Fugitive, and Free Willy. The Japanese lineup of titles was different. A series of releases under the banner 'SQUEEZE LD' from Pioneer of mostly Carolco titles included Basic Instinct, Stargate, Terminator 2: Judgment Day, Showgirls, Cutthroat Island, and Cliffhanger. Oddly enough Terminator 2 was released twice in Squeeze LD, the second release being THX certified and a notable improvement over the first.

Recordable formats

Another type of video media, CRVdisc, or 'Component Recordable Video Disc' were available for a short time, mostly to professionals. Developed by Sony, CRVdiscs resemble early PC CD-ROM caddies with a disc inside resembling a full sized LD. CRVdiscs were blank media that could be recorded once on each side (much like WORM media, such as CD-R discs). CRVdisc was rarely used by the consumer due to the high cost of the equipment and media, and were used largely for backup storage in professional/commercial applications.

Another form of recordable laserdisc that is completely playback-compatible with the Laserdisc format (unlike CRVdisc, due to its caddy enclosure) is the RLV, or Recordable LaserVision disc. It was developed and first marketed by the Optical Disc Corporation (ODC, now ODC Nimbus) in 1984. RLV discs, like CRVdisc, are also a WORM technology, and function exactly like a CD-R disc. RLV discs look almost exactly like standard laserdiscs, and can play in any standard laserdisc player after they've been recorded. The only difference an RLV disc has over regular factory-pressed laserdiscs is their reflective purple-violet color resulting from the dye embedded in the reflective layer of the disc to make it recordable, as opposed to the silver mirror appearance of regular LDs. The color of RLVs look almost exactly like the purplish color of the dye used for some DVD-R and DVD+R discs. RLVs were popular for making short-run quantities of laserdiscs for specialized applications such as interactive kiosks and flight simulators.

Wikipedia information about Laserdisc. This article is licensed under the GNU Free Documentation License . It uses material from the Wikipedia article 'Laserdisc'