Laserdisc

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Not to be confused with disk laser, a flat-configuration solid-state laser.
Laserdisc

A LaserDisc (left), compared with a DVD.
Media type Optical disc
Encoding NTSC, PAL
Capacity 60 minutes per side CLV
30 minutes per side CAV
Developed by Philips & MCA
Usage Home video
Data Storage
Optical disc authoring
Optical media types
Discontinued Optical Disc Formats
Standards
Further reading
This box: view • talk • edit
Laserdisc certification mark

The Laserdisc (LD) is an obsolete home video disc format, and was the first commercial optical disc storage medium. Initially marketed as Discovision in 1978, the technology was licensed and sold as Reflective Optical Videodisc, Laser Videodisc, Laservision, Disco-Vision, DiscoVision, and MCA DiscoVision until Pioneer Electronics purchased the majority stake in the format and marketed LaserDisc in the mid to late 1980s.

While technologically superior to the then rival VHS and Betamax systems, the laserdisc never obtained more than a niche market with videophiles in America. In Japan, the format was better supported and thus more prevalent. In Europe, it remained largely an obscure format. The technology and concepts provided with the Laserdisc would become the forerunner to Compact Discs and DVDs.

Contents

[edit] History

Laserdisc technology, using a transparent disc[1], was invented by David Paul Gregg in 1958 (and patented in 1961 and 1990)[2][3]. 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. Laserdisc was first available on the market, in Atlanta, on December 15, 1978, two years after the VHS VCR and four 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. Several of the scientists responsible for the early research (Richard Wilkinson, Ray Deakin and John Winslow) founded Optical Disc Corporation (now ODC Nimbus).

In 1979, the Museum of Science and Industry in Chicago opened their "Newspaper" exhibit which used interactive Laserdiscs to allow visitors to search for the front page of any Chicago Tribune newspaper. This was a very early use of digitally interactive technology in Museums and could even be among the first.[citation needed]

The first Laserdisc title marketed in North America was the MCA DiscoVision release of Jaws in 1978. The last two titles released in North America were Paramount's Sleepy Hollow and Bringing Out the Dead in 2000. A dozen or so more titles continued to be released in Japan, until the end of 2001. The last Hong Kong-released Laserdisc-format movie title was Tokyo Raiders. Production on Laserdisc players did not stop until January 2009 when Pioneer stopped making them. The format was released in 1981 and a total of 3.6 million Laserdisc players were sold in Japan.[4]

It was estimated that in 1998, Laserdisc players were in approximately 2% of US households (roughly two million).[5] By comparison, in 1999, players were in 10% of Japanese households.[6] Laserdisc 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, the Laserdisc has always remained an obscure format. The format was, however, chosen by the British Broadcasting Corporation (BBC) for the BBC Domesday Project in the mid-1980s, a school-based project to commemorate 900 years since the original Domesday Book in England.

[edit] Technical information

The standard home video laserdisc is 30 cm (11.81 inches) in diameter and made up of two single-sided aluminum discs layered in plastic. Although read and featuring properties similar to a compact disc or DVD, a Laserdisc is for the most part an entirely analog system with video stored in the composite domain with analog sound and/or some form of digital audio. The first laserdiscs featured in 1978 were entirely analog but the format evolved to incorporate simple digital stereo sound to multi-channel formats such as Dolby Digital and DTS.

Since digital encoding and compression schemes were either unavailable or impractical in 1978, three encoding formats based on the rotation speed were used:

  • CAV (Constant Angular Velocity) or Standard Play discs supported 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 crosstalk 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. One of the most intriguing advantages of this format was the ability to reference every frame of a film directly by number—a feature of particular interest to film buffs, students and others intrigued by the study of errors in staging, continuity etc.
  • 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 per side, or 2 hours per disc. For films with a run–time less than 120 minutes, this meant they could fit on a single disc, lowering the cost of the title and eliminating the distracting exercise of "getting up to change the disc"—at least for those who owned a dual-sided player. The vast majority of titles were only available in CLV. (A few titles were released partly CLV, partly CAV. For example, a 140-minute movie could fit on two CLV sides, and one CAV side, thus allowing for the CAV-only features during the climax of the film.)
  • 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 in a steady linear pace as a CLV disc is read. With the exception of 3M/Imation, all Laserdisc manufacturers adopted the CAA encoding scheme, although the term was rarely (if ever) used on any consumer packaging.

As Pioneer introduced Digital Audio to Laserdisc in 1985, they further refined the CAA format. CAA55 was introduced in 1985 with a total playback capacity of 55 minutes 5 seconds, and was necessary to resolve technical issues with the inclusion of Digital Audio. Several titles released between 1985 and 1987 were analog audio only due to the length of the title and the desire to keep the film on 1 disc (e.g., "Back to the Future"). By 1987, Pioneer had overcome the technical challenges and was able to once again encode in CAA60—allowing a total of 60 minutes, 5 seconds. Pioneer further refined CAA, offering CAA45—encoding 45 minutes of material, but filling the entire playback surface of the side. Used on only a handful of titles, CAA65 offered 65 minutes 5 seconds of playback time. The final variant of CAA is CAA70, which could accommodate 70 minutes of playback time. There are not any known uses of this format on the consumer market.

All of these timing parameters are based on the NTSC standard of 30fps. The PAL and SECAM standards of 25fps increases the playback capacity of all the various formats by 20%.

[edit] 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 encoded channels, (EFM, CIRC, 16 bit and 44.1 kHz sample rate)[7]. 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. The digital sound signal in both formats are EFM-encoded as in CD[7]. 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.[8] 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.

The two FM audio channels occupied the disc spectrum at 2.3 and 2.8 MHz on NTSC formatted discs and each channel had a 100 kHz FM deviation. The FM audio carrier frequencies were chosen to minimize their visibility in the video image, so that even with a poorly mastered disc, audio carrier beats in the video will be at least -35db down, and thus, invisible. Due to the frequencies chosen, the 2.8MHz audio carrier (Right Channel) and the lower edge of the chroma signal are very close together and if filters are not carefully set during mastering, there can be interference between the two. In addition, high audio levels combined with high chroma levels can cause mutual interference, leading to beats becoming visible in highly saturated areas of the image. To help deal with this, Pioneer decided to implement the CX Noise Reduction System on the analog tracks. By reducing the dynamic range and peak levels of the audio signals stored on the disc, filtering requirements were relaxed and visible beats greatly reduced or eliminated. The CX system gives a total NR effect of 20db, but in the interest of better compatibility for non-decoded playback, Pioneer reduced this to only 14db of noise reduction (the RCA CED system used the 'original' 20db CX system). This also relaxed calibration tolerances in players and helped reduce audible pumping if the CX decoder wasn't calibrated correctly.

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 components, and many early discs had poorly mastered 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 far 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 analog discs also applied CX Noise Reduction, which improved the signal-noise ratio of their audio.

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 audio channel to the modulated AC-3 stream. If the player did not have an AC-3 decoder available, the next most attractive playback option would be the digital Dolby Surround or stereo audio tracks. If either the player did not support digital audio tracks (common in older players), or the disc did not include digital audio tracks at all (uncommon for a disc which is mastered with an AC-3 track), the only remaining option was to fall back to a monophonic presentation of the left analog audio track. However, many older analog-only players not only failed to decode AC-3 streams, but weren't even aware of their potential existence. Such a player will happily play the analog audio tracks verbatim, resulting in garbage output in the right channel.

On a DTS disc, digital PCM audio is not available, so if a DTS decoder was also not available, the only option is to fall back to the analog Dolby Surround or stereo audio tracks. In some cases, the analog audio tracks were further made unavailable through replacement with supplementary audio such as isolated scores or audio commentary. This effectively reduced playback of a DTS disc on a non-DTS equipped system to mono audio—or in a handful of cases, no film soundtrack at all.[9]

Only one 5.1 surround sound option existed on a given Laserdisc (either Dolby Digital or DTS), so if surround sound is desired, the disc must be matched to the capabilities of the playback equipment (LD Player and Receiver/Decoder) by the purchaser. A fully capable Laserdisc playback rig includes a newer Laserdisc player that is capable of playing digital tracks, has a digital optical output for digital PCM and DTS audio, is aware of AC-3 audio tracks, and has an AC-3 coaxial output; an external or internal AC-3 RF demodulator and AC-3 decoder; and a DTS decoder. Many A/V receivers combine the AC-3 decoder and DTS decoder logic, but an integrated AC-3 demodulator is rare both in Laserdisc players and in newer A/V receivers.[10]

[edit] Hardware

The earliest players used Helium-neon laser tubes to read the media with red-orange light, while later players used infrared semiconductor laser diodes. Many Pioneer VP-1000, LD-1100, LD-660 and PR-8210s are still in good working order. Pioneer used very high-quality Helium-Neon laser tubes in their players and, unlike the Magnavox Magnavision players (VH-8000, VH-8005), 'out-gassing' of the laser tube in a Pioneer player is a rare event. Optical hobbyists have also been known to cannibalize the laser tube machines. From 1978 until 1984, basically all LaserDisc players, either industrial or consumer, used Helium-Neon laser tubes.

In March 1984, Pioneer introduced the first consumer player with a solid-state laser, the LD-700. It was also the first LD player to load from the front and not the top. One year earlier Hitachi introduced an expensive industrial player with a laser diode, but the player was made only in limited quantities. After Pioneer released the LD-700, laser tubes were no longer used in consumer players, despite their advantages, though Philips continued to use laser tubes in their industrial units for a short time after. Helium-Neon lasers had a tighter, lower wavelength laser that created a smaller spot on the disc, leading to better tracking. In addition, the laser tube generated less photon-shot noise than the solid-state diode laser, resulting in a less-noisy picture on-screen.

The picture produced by a solid-state based LD player could be instantly recognized; it was slightly softer and large expanses of color, such as a blue sky in the image, would have a tendency to have small streaks across it. Also, the infrared diode laser did not cope as well with disc defects requiring "fast" response, such as dirt trapped under the surface of the disc (inclusions), an off-center hole or track errors caused during mastering. Because of this, collectors with large MCA DiscoVision collections tended to use their tube-based LaserDisc players for playback of these discs since DiscoVision discs were riddled with just these sorts of defects. In addition to being the first LD player to use a laser diode, the Pioneer LD-700 was also the first player ever to have a 'tilt' mechanism for tracking. This could measure any warp of the laser disc and physically tilt the laser to maintain accurate tracking — which greatly reduced crosstalk on CLV Extended Play discs — arguably, the tilt-servo was one of the greatest advances in the format.

Most machines made were single-sided; players which required manually turning the disk over to play the other side. A number of players were made that were double-sided, in that the machine could automatically reverse the spin direction and move the pickup head to the other side of the disk. While Pioneer produced some industrial "jukeboxes" that held more than 50 discs, only one consumer player, the LD-W1, could hold more than a single disc; the W1 held two discs and could automatically change discs and sides by rotating the entire mechanism, including both the laser and turntable. Electrically, the LD-W1 was the internal circuitry of the Elite LD-S1 combined with the disc/side changing mechanism.

Many Laserdisc players manufactured from the late 1980s through the time of the format's end had both composite (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 yielded 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 may yield better results.[citation needed]

[edit] Combi-players

Most players made after the mid-1980s were capable of also playing audio CDs. These players included a 12 cm (4.7 in) indentation in the loading tray, where the CD would be placed for play. At least one Pioneer model also operated as a CD-changer, with several 12 cm indentations around the circumference of the main tray.

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, 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 Pioneer DVL-909 lacks support for DTS output. However, a modification to the player can allow this player to support DTS streams on DTS discs, essentially turning the DVL-909 into a Pioneer Elite DVL-91.

The last model DVD/LD player was the Japanese only DVL-H9, but the older 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 competent, 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. Manufacturing of the DVL-919 continued until January 1, 2009 when Pioneer announced [11] that production would cease after a final production run of 3000 DVL-919 and other model laser disc players.

[edit] High-end Japanese players

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 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.

[edit] PAL Laserdiscs

PAL laserdiscs had a longer playing time than NTSC discs, but had fewer audio options. PAL discs only have 2 audio tracks, consisting of either 2 analog-only tracks on older PAL LDs, or 2 digital-only tracks on newer discs. In comparison, newer NTSC LDs have 4 tracks, 2 digital and 2 analog altogether, with one of the analog tracks sometimes being used to carry a modulated AC-3 signal for 5.1 channel audio (for decoding and playback by newer LD players with an "AC-3 RF" output). However, older NTSC LDs made before 1984 (such as the original DiscoVision discs) only have 2 analog audio tracks.

[edit] Branding

Laserdisc Cover for Tiny Toon Adventures: How I Spent My Vacation

During its development, MCA, which co-owned the technology, referred to it as the Optical Videodisc System, "Reflective Optical Videodisc" or "Laser Optical Videodisc", depending on the document; changing the name once in 1969 to Disco-Vision and then again in 1978 to DiscoVision (without the hyphen), which became the official spelling. Technical documents and brochures produced by MCA Disco-Vision during the early and mid-'70s also used the term "Disco-Vision Records" to refer to the pressed discs. MCA owned the rights to the largest catalog of films in the world during this time, and they manufactured and distributed the DiscoVision releases of those films under the "MCA DiscoVision" software and manufacturing label — consumer sale of those titles beginning on December 15, 1978.

Philips' preferred name for the format was "VLP", after the Dutch words Video Langspeel-Plaat, which in English-speaking countries stood for Video Long-Play. The first consumer player, the Magnavox VH-8000 even had the VLP logo on the player. For a while in the early and mid-'70s, Philips also discussed a compatible audio-only format they called "ALP", but that was soon dropped as the Compact Disc system became a non-compatible project in the Philips corporation. Until early 1981, the format had no 'official' name; however, the LaserVision Association, made up of MCA, Universal-Pioneer and Philips/Magnavox, was formed to standardize the technical specifications of the format (which had been causing problems for the consumer market) and finally named the system officially as "LaserVision".

In Europe, the format was introduced in 1983 with the LaserVision name although Philips used "VLP" in model designations, such as VLP-600. Philips tried renaming the entire format in 1987 to "CD-Video", and while the name and logo appeared on players and labels for years, the 'official' name of the format remained LaserVision. In the early 1990s, the format's name was finally changed to LaserDisc.

[edit] Pioneer

Pioneer Electronics also entered the optical disc market in 1977 as a 50/50 joint-venture with MCA called Universal-Pioneer and manufacturing MCA designed industrial players under the MCA DiscoVision name (the PR-7800 and PR-7820). For the 1980 launch of the first Universal-Pioneer player, the VP-1000, the name became Laser Disc (with a 'rainbow' type logo joining the two words) and in 1981 the intercap was eliminated and "LaserDisc" became the final and common nickname for the format, although the official name was LaserVision. However, as Pioneer reminded numerous video magazines and stores in 1984, LaserDisc was a trademarked word, standing only for LaserVision products manufactured for sale by Pioneer Video or Pioneer Electronics. A 1984 Ray Charles ad for the LD-700 player bore the term "Pioneer LaserDisc brand videodisc player." From 1981 until the early '90s, all properly licensed discs carried the LaserVision name and logo, even Pioneer Artists titles.

The Laserdisc turtle, used on the non-program side of some single sided Laserdiscs

On single sided Laserdiscs mastered by Pioneer, playing the wrong side will cause a still screen to appear with a happy, upside down turtle that has a Laserdisc for a stomach (nicknamed the "Laserdisc Turtle"). The words "Program material is recorded on the other side of this disc" are below the turtle. Other manufacturers used a regular text message without graphics.

[edit] MCA

During the early years, MCA also manufactured discs for other companies including Paramount, Disney and Warner Bros. Some of them added their own names to the disc jacket to signify that the movie was not owned by MCA. After Discovision Associates shut down in early 1982, Universal Studio's videodisc software label, called MCA Videodisc until 1984, began reissuing many DiscoVision titles. Sadly, quite a few, such as Battlestar Galactica and Jaws, were time-compressed versions of their CAV or CLV DiscoVision originals. The time-compressed CLV re-issue of Jaws no longer had the original soundtrack, having had incidental background music replaced for the videodisc version due to licensing cost (the music wouldn't be available until the THX LaserDisc box set was released in 1995). One Universal/Columbia co-production issued by MCA DiscoVision in both CAV and CLV versions, The Electric Horseman, is still not available in any other home video format with its original score intact; even the most recent DVD release has had substantial music replacements of both instrumental score and Willie Nelson's songs.

[edit] Pioneer PR7820

The Pioneer PR7820 was first mass-produced industrial laserdisc player — sold originally as the MCA DiscoVision PR-7820. This unit was used in many GM dealerships as a source of training videos and presentation of GM's new line of cars and trucks in the late '70s and early '80s. After MCA DiscoVision shut down, Pioneer continued to sell the player under the Pioneer name as the Pioneer Model-III. Was a full Level-III player and could accept a data-dump from discs themselves. Could also be controlled by an external computer as well as gen-locked to external video sources.

The 7820 is the only player ever sold to either the industrial or consumer market that was entirely designed and engineered by the technicians at MCA Disco-Vision and contained all of their preferred design approaches, such as playing the disc with the laser on top (instead of underneath) and moving the disc radially to provide tracking instead of moving the laser radially. MCA engineers designed the player at the DiscoVision labs in Torrance, CA and Universal-Pioneer mass produced it in Japan. The 7820 was such a high quality player that MCA themselves used it at their DiscoVision disc pressing plant in Carson, CA for quality control checks of both master discs and finished sets. Unfortunately, this caused problems because the 7820 could easily play discs that the poorly designed and quite primitive consumer player, the Magnavox VH-8000, simply couldn't cope with.

In 1980, Discovision Associates released a factory update (it could also be retrofitted to existing 7820s) that reduced disc search times to less than 3 seconds, and added the ability to jump up to 99 tracks during vertical blanking, giving essentially "instant" searches. An external computer interface box was also made available at the same time which contained additional memory that increased the total size of a disc-based computer program the 7820 could store and execute to 256k.

The 7820 was the first LD player to use solid-state tangential tracking — instead of a tangential tracking mirror, the 7820 used an electronic CCD delay line to provide tangential tracking corrections, giving the player superb color quality. It wasn't until 1985/6 that the tangential mirror began to be replaced by electronic correction, first by Yamaha in their first consumer LD player, and eventually, by Pioneer themselves.

MCA DiscoVision had no suggested retail price for the PR-7820; depending on the number purchased, it varied from $3,500 to $2,200 per unit if more than 1000 were bought at once. Fully functional 7820s are not easily available on eBay and are nearly impossible to find in fully functional condition. Because they are made of steel, weight is a problem for shipping the units.

[edit] Other significant players

[edit] Laserdisc vs. VHS

LD had a number of advantages over VHS. It featured a far sharper picture with a horizontal resolution of 425 TVL lines for NTSC[citation needed] and 440 TVL lines for PAL discs, while VHS featured only 240 TVL lines with NTSC. 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. 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, and the duplication process was much simpler. A VHS cassette has at least 14 parts including the actual tape while laserdisc has one part with five or six layers. A disc can be stamped out in a matter of seconds; duplicating videotape required a complex bulk tape duplication mechanism and was a timeconsuming process.

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 (however, see Laser rot, below). By contrast, a VHS tape holds all of its picture and sound information on the tape in a magnetic coating which is in contact with the spinning heads on the head drum, 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 or malfunctioning model) to mishandle the tape and damage it by creasing it, frilling (stretching) its edges, or even breaking it.

[edit] Special editions

The format's support for multiple audio tracks allowed for vast supplemental materials to be included on-disc and made it the first available 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,[citation needed] 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.

[edit] Disadvantages of Laserdiscs

Despite the apparent advantages over competing technology at the time (namely VHS), the format was not without its flaws. The discs were 12" in diameter, heavy, cumbersome, easier than a VHS cassette to damage when handling, and manufacturers did not market LD units with recording capabilities to consumers. Also, because of their size, greater mechanical effort was required to spin the discs at the proper speed, resulting in much more noise generated than other media.

In addition, perfect still frames and random access to individual still frames were limited only to the more expensive CAV discs, which only had a playing time of approximately 30 minutes per side. In later years, Pioneer and other manufacturers overcame this limitation by incorporating a digital memory buffer, which "grabbed" a single frame from a CLV title.

Despite their large physical size, the space-consuming analog video signal of a Laserdisc limited playback duration to 30 (CAV) or 60 minutes (CLV) per side because of the hardware manufacturer's refusal to reduce line count for increased playtime. 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. One exception to this rule is the Pioneer LD-W1, which had two disc platters.

[edit] Laser rot

Main article: Laser rot

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.[citation needed] The adhesive contained impurities that were able to penetrate the lacquer seal layer and chemically attack the metalized reflective aluminium layer, causing it to oxidize and lose its reflective characteristics. This was a problem that was coined "laser rot" (or, "LaserRot", after the original official pascal-case "LaserDisc" name of the underlying product) among LD enthusiasts. Some forms of laser rot could appear as black spots that looked like mold or burned plastic which would cause the disc to skip and the movie to exhibit excessive speckling noise. But, for the most part, rotted discs may actually appear perfectly fine to the naked eye.

Later optical standards have been known to suffer similar problems, including a notorious batch of defective CDs manufactured by Philips-DuPont Optical in Europe during the early 1990s.

Coincidentally, the Laserdisc movie that has the most reported laser rot is the film Eraser (1996), as noted by the contributors of LaserDisc Database. The discs for this title were replicated by Sony Digital Audio Disc Corporation, U.S., in Terre Haute, Indiana.

[edit] Laserdisc vs. DVD

[edit] Video

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 so adequately, these two signals cannot be completely separated. On DVDs, data is stored in the form of blocks which make up each independent frame. The signal produced is dependent on the equipment used to master the disc. Signals range from composite and split, to YUV and RGB. Depending upon which format is used, this can result in far higher fidelity, particularly at strong colour borders or regions of high detail (especially if there is moderate movement in the picture) and low-contrast details like skin tones, where comb filters almost inevitably smudge some detail.

Compared to the entirely digital DVD, Laserdiscs use only analog video. As the Laserdisc format is not digitally encoded and does not make use of compression techniques, it is immune from video 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. However, proprietary human-assisted encoders manually operated by specialist experts can vastly reduce the incidence of artifacts.

[edit] Audio

DVDs almost exclusively use compressed audio formats such as Dolby Digital and DTS which offer multichannel sound. Most Laserdiscs were encoded with stereo (often Dolby Surround) CD quality audio 16bit/44kHz tracks as well as analog audio tracks.[12] Many later release Laserdiscs included Dolby Digital and DTS audio tracks but at slightly lower bitrates than DVD.

[edit] Disadvantages of Laserdiscs

Given the analog nature of Laserdiscs, without any forms of checksum or error correction, slight dust and scratches cause various problems that could affect video quality. Wearout and/or calibration drift on the playback hardware also play a role in degrading video quality, audio quality, and tracking accuracy. In contrast, the DVD format's digital nature and error correction ensures that the signal from a damaged disc will remain identical to that from a perfect disc right up until read errors become so bad as to prevent the disc from producing any usable data.

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 comes up when the optical pickup inside the player accidentally picks up the encoded video information from a track adjacent to where it was reading on the disc. The added information shows up as distortion in the picture, 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. 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", 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.

On most television sets a given DVD player will produce a picture that is visually indistinguishable from other units, and quality differences between players only becomes easily apparent with higher-end equipment due to some post-processing of the MPEG-2 stream. In contrast, Laserdisc playback quality is highly dependent on hardware decoder quality (as with any analog format). Major variances in picture quality could appear between different makes and models of LD players, even when tested on a low to mid-range television. This had long lasting ramifications, as the pricing for high end players has remained comparably high (anywhere from US$200 to well over $1,000), while older and less desirable players can be purchased in working condition for as little as $25.

[edit] Advantages of Laserdiscs

Laserdisc players were known to provide the operator with a great degree of control over the playback process. Unlike many DVD players, the operator is immediately tied to the transport mechanism: pause, fast-forward, and fast-reverse commands are always accepted. There were no "User Prohibited Options" where content protection code instructs the player to refuse commands to skip a specific part (such as fast forwarding through an FBI warning). However, some DVD players, particularly in the higher-end units, have the ability to ignore the blocking code and play the video without restrictions. With CAV laserdiscs the user can access each individual frame of a video; a feature not common among DVD players.[citation needed] However, Some DVD players have cache features which stores a certain amount of the video in RAM which allows the player to index a DVD as quickly as an LD, even down to the frame in some players.

While Dolby Digital and DTS offer multichannel sound, many Laserdisc enthusiasts claim that the uncompressed PCM tracks can often outperform the respective DVDs of a title in richness and depth (and, because of the ways in which 5.1 tracks are often mastered, in dimension as well). One important factor in newer DVD releases' small advancement over Laserdiscs is their opting for 16bit/44kHz sound in lieu of the DVD standard's little-known 24bit/96kHz capabilities.

Another advantage of Laserdisc is that damaged spots can be skipped, while a DVD will become unusable. Some newer DVD players feature a repair+skip algorithm, which alleviates this problem by continuing to play the disc, filling in unreadable areas of the picture with blank space or a frozen frame of the last readable image and sound. The success of this feature depends upon the amount of damage. Laserdisc players, when working in full analog, recover from such errors faster than DVD players. Direct comparison is, however, almost impossible due to the differences between the two media. A 1" scratch on a DVD will probably cause more problems than a 1" scratch on an Laserdisc, but a fingerprint taking up 1% of the area of a DVD would almost certainly cause fewer problems than a similar mark covering 1% of the surface of an Laserdisc.

Some Laserdisc proponents believe analog laserdisc is theoretically capable of higher quality than the "lossy" quality of DVD. Early DVD demo discs often had compression or encoding problems, lending additional support to such claims at the time. However, "LD-perfection" is rarely achieved in practice. Only the best LDs in the best playback systems exhibit such superior quality in comparison to the newer DVDs. Proponents of Laserdisc argue that Laserdisc maintains a "smoother", more "film-like" image while DVD still looks slightly more artificial. This is similar to the CD versus LP sound quality debates common in the audiophile community.

[edit] Comparison to other media

This is a list of modern-day, digital-type measurements (and traditional, analog horizontal resolutions in TV lines per picture height) for various media. The list only includes popular formats, not rare formats, and all values are approximate (rounded to the nearest 10), since the actual quality can vary machine-to-machine or tape-to-tape. For PAL media, replace 480 with 576 and 240 with 288. For ease-of-comparison all values are for the NTSC system, and listed in ascending order from lowest quality to highest quality.

[edit] Success of the format

The format was not well-received outside of videophile circles in North America due in large part to the high cost of the players and discs, which were far more expensive than VHS decks and tapes, and due to marketplace confusion with the technologically inferior SelectaVision, which also went by the name Videodisc. However, the Laserdisc format was more popular in Japan than in North America because 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, who sought the higher video and sound quality of laserdisc and the availability of numerous titles not available on VHS. Laserdiscs were also popular alternatives to videocasettes among movie enthusiasts in the more affluent regions of South East Asia, such as Singapore, due to their high integration with the Japanese export market and the disc-based media's superior longetivity compared to videocassette, especially in humid conditions.

The format also became quite popular in Hong Kong during the 1990s before the introduction of VCDs and DVD; although people rarely bought the discs, high rental activity helped the video rental business in the city grow larger than it had ever been previously. Interestingly, NTSC laserdiscs were used in the Hong Kong market, in contrast to the PAL standard used for broadcast. The standard conversion was effected in the player.

Despite the mild popularity, manufacturers refused to market recordable Laserdisc devices on the consumer market, even though the competing VCR devices could record onto cassette, which hurt sales worldwide. The inconvenient disc size, the high cost of both the players and the media and the inability to record onto the discs combined to take a serious toll on sales, and contributed to the format's mediocre adoption figures.

Although the Laserdisc format has been supplanted by DVD, 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.

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 Encyclopædia Britannica films reproducing classic experiments in the field which are difficult or impossible to replicate in the laboratories in educational settings.[13] These films have now been released on DVD.[14]

[edit] Laserdisc variations

[edit] Computer control

Early in the eighties, Philips produced a Laserdisc 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 1986, a SCSI equipped Laserdisc player attached to a BBC Master computer was used for the BBC Domesday Project.

Apple's HyperCard scripting language provided Macintosh computer users with a means to design databases of slides, animation, video and sounds from Laserdiscs and then to create interfaces for users to play specific content from the disc. User-created "stacks" were shared and were especially popular in education where teacher-generated stacks were used to access discs ranging from art collections to basic biological processes. Commercially available stacks were also popular with the Voyager company being possibly the most successful distributor.[15]

Commodore International's 1992 multimedia presentation system for the Amiga, AmigaVision, included device drivers for controlling a number of Laserdisc players through a serial port. Coupled with the Amiga's ability to use a Genlock, this allowed for the Laserdisc video to be overlaid with computer graphics and integrated into presentations and multimedia displays, years before such practice was commonplace.

Pioneer also made computer-controlled units such as the LD-V2000. It had a back-panel RS-232 serial connection through a 5-pin DIN connector, and no front-panel controls except Open/Close. (The disc would be played automatically upon insertion.)

Under contract from the U.S. Military, Matrox produced a combination computer laserdisc player for instructional purposes. The computer was a 286, the laserdisc player only capable of reading the analog audio tracks. Together they weighed 43 pounds and sturdy handles were provided in case 2 people were required to lift the unit. The computer controlled the player via a 25-pin serial port at the back of the player and a ribbon cable connected to a proprietary port on the motherboard. Many of these were sold as surplus by the military during the 90s, often without the controller software. It is nevertheless possible to control the unit by removing the ribbon cable and connecting a serial cable directly from the computer's serial port to the port on the laserdisc player.

[edit] Video games

Main article: Laserdisc video game

A number of companies used the Laserdisc format as the basis for arcade video games during the 1980s and early 1990s, most notably Dragon's Lair and Space Ace. Hardware in the arcade cabinet jumped to various scenes on the Laserdisc according to the player's actions. The ability of Laserdisc to use full-motion video provided significantly more detailed and complex visuals (although at the expense of interactivity due to the non-realtime nature of the format) than the simplistic sprite-based graphics of other arcade games at the time. Significant players in the Laserdisc video game market included American Laser Games and Cinematronics.

[edit] MUSE LD

In 1991, several manufacturers announced specifications for what would become known as MUSE Laserdisc, representing a span of almost 15 years until the feats of this HD analog optical disc system would finally be duplicated digitally by HD DVD and Blu-ray. 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 superior in performance to non-MUSE players even with these NTSC discs. 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. There are televisions with MUSE decoding built-in and set top tuners with decoders that can provide the proper MUSE input. Equipment prices were high, especially for early HDTVs which generally eclipsed US$10,000, 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: Judgement 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.

[edit] Laserdisc sizes

The most common size of Laserdisc was 30 centimetres (12 in). These approximated the size of LP vinyl records. These discs allowed for 30 minutes per side (CAV) or 60 minutes per side (CLV). The vast majority of programming for the Laserdisc format was produced on these discs.

20 cm (7.9 in) Laserdiscs were also published. These "EP"-sized LDs allowed for 20 minutes per side (CLV). They are much rarer than the full-size LDs, especially in North America. These discs were often used for music video compilations (e.g., Bon Jovi's "Breakout", Bananarama's "Video Singles" or T'Pau's "View From A Bridge"[citation needed]).

There were also 12 cm (4.7 in) "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. The original 1989 release of David Bowie's restrospective Sound and Vision CD box set prominently featured a CD-V video of Ashes To Ashes, and standalone promo CD-Vs featured the video, plus 3 audio tracks: John, I'm Only Dancing, Changes and The Supermen.

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.

[edit] Picture discs

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.

[edit] LD-G

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).

[edit] LaserActive

Main article: Pioneer LaserActive

Pioneer also marketed a format similar to LD-G, called LD-ROM. It was used by Pioneer's LaserActive interactive Laserdisc player/video game console introduced in 1993, and contained analog video and audio, in combination with digital data (where the digital audio tracks would be on regular Laserdiscs). LD-ROM was used for several games that could be played on the LaserActive player/console.

[edit] Squeeze LD

With the release of 16:9 televisions in the mid 1990s, Pioneer and Toshiba decided that it was time to 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 same procedure was used for DVD. Unlike most DVD players, very few LD players had the ability to unsqueeze the image for 4:3 sets. If the discs 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 viewers had 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.

[edit] Recordable formats

A Pioneer LaserRecorder that could be connected to a computer or a video source
A CRV Disc with a VHS tape for size comparison

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, write-once, read-many media that could be recorded once on each side. CRVdiscs were used largely for backup storage in professional/commercial applications.[citation needed]

Another form of recordable Laserdisc that is completely playback-compatible with the Laserdisc format (unlike CRVdisc with 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 cosmetic difference between an RLV disc and a regular factory-pressed Laserdiscs is their reflective purple-violet (or blue with some RLV discs) 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 purplish color of RLVs is very similar to 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.

In spite of nonrecordability being commonly regarded as the primary weakness of the Laserdisc format, these recordable LD systems were never marketed toward the general public, and are so poorly known as to create the misconception that a home recording system for Laserdiscs is impossible.

[edit] In popular culture

  • An early single-sided prototype DiscoVision Laserdisc made an appearance in the 1977 movie Airport '77, during a scene in which a flight stewardess inserts it into what looks like a Magnavox VH-8000 "Magnavision" player for an in-flight movie.
  • In Back to the Future, an MCA LaserDisc hangs on the wall amongst Doc Brown's clocks. In Back to the Future Part II, Laserdiscs are seen bundled up and left out as garbage when Doc and Marty leave Jennifer after their arrival in the year 2015, suggesting that they have become undesireable.
  • Laserdisc players were used for the videos on the Back to the Future ride. The Ride in Hollywood closed on September 1, 2007, while the Florida version closed on March 30, 2007.
  • A LaserDisc player appears briefly in the 1989 Bond film, Licence to Kill in Felix Leiter's study as well as in a number of other scenes. Philips was a major sponsor of the film.
  • During the late 1980s, Pioneer signed contracts with major music artists, such as Madonna, Janet Jackson, and others, to release their concerts on Laserdisc only through Pioneer. To this date, the contracts are still standing, and the concerts have not been re-released on DVD by Pioneer or others. An exception is the Genesis Laserdisc of "The Way We Walk" , which was released to DVD in October 2002, under the Pioneer label.[citation needed]

[edit] See also

[edit] References

  1. ^ U.S. Patent 3,430,966  Transparent recording disc, 1969.
  2. ^ U.S. Patent 3,530,258  Video signal transducer, 1970.
  3. ^ U.S. Patent 4,893,297  Disc-shaped member, 1990.
  4. ^ "News of laser disk player production end". 2009-01-14. http://pioneer.jp/press/2009/0114-1.html. Retrieved on 2009-03-09. 
  5. ^ "New and emerging video technologies: A status report". October 29, 1998. http://www.dlib.indiana.edu/~brancoli/videostatus.html. Retrieved on 2007-10-05. 
  6. ^ "Bittersweet Times for Collectors of Laser Disk Movies". April 29, 1999. http://query.nytimes.com/gst/fullpage.html?res=9D0CE5DD123DF93AA15757C0A96F958260&sec=&spon=&pagewanted=print. Retrieved on 2007-10-05. 
  7. ^ a b "Digital audio modulation in the PAL and NTSC video disc formats, J. Audio Eng. Soc. vol. 32, pp. 883, 1984". http://www.aes.org/e-lib/browse.cfm?elib=11765. Retrieved on 2008-02-24. 
  8. ^ "Laserdisc Forever Review of Star Wars Episode 1: The Phantom Menace". May 9,2000. http://www.mindspring.com/~laserdisc-forever/phantommenace.htm. Retrieved on 2007-10-05. 
  9. ^ "DTS Digital Surround LaserDisc". January 24, 2005. http://www.blam1.com/LaserDisc/dts.htm. Retrieved on 2007-07-20. 
  10. ^ "LaserDisc FAQ". PrecisionLaserdisc.com. http://www.precisionlaserdisc.com/newfaq.html. Retrieved on 2007-07-20. 
  11. ^ http://pioneer.jp/press/2009/0114-1.html
  12. ^ "(2.7) How does DVD compare to laserdisc?". AllforMP3.com. http://www.allformp3.com/dvd-faqs/27.htm. Retrieved on 2007-07-20. 
  13. ^ Kay Hansen Littler. "Physics: CINEMA CLASSICS". Department of Physics, University of North Texas. http://www.phys.unt.edu/~klittler/demo_room/MultiMedia/CINCLSS.html. Retrieved on 2007-07-20. 
  14. ^ AAPT. "Physics: CINEMA CLASSICS". AAPT. http://www.aapt.org/Store/cinemaclassics.cfm. Retrieved on 2008-01-15. 
  15. ^ Jeff Martin. "Voyager Company CD-ROMs: Production History and Preservation Challenges of Commercial Interactive Media" (PDF). Electronic Arts Intermix (EAI) Resource Guide. http://resourceguide.eai.org/preservation/computer/pdf-docs/voyager_casestudy.pdf. Retrieved on 2007-07-20. 

[edit] Resources

  • Jordan Isailovic, Videodisc and Optical Memory Systems Vol. 1, Boston: Prentice Hall, 1984. ISBN 978-0139420535
  • Lenk, John D. Complete Guide to Laser/VideoDisc Player Troubleshooting and Repair. Englewood Cliffs, N.J.: Prentice-Hall, 1985. ISBN 0-13-160813-4.

[edit] External links

Sister project Wikimedia Commons has media related to: Laserdisc
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