Laser disc
| Storage medium Laser disc
|
|
|
|
| General | |
|---|---|
| Type | Optical storage medium |
| capacity | PAL disc per side: 64 min. (CLV), 32 min. (CAV) NTSC disc per side: 60 min. (CLV), 30 min. (CAV) |
| size | 30/20/12 cm (diameter) |
| use | Data storage, analog films |
| origin | |
| developer | MCA , Philips , Pioneer |
| Launch | 1978 |
| successor | DVD |
The laser disc ( LD ), also known as a laser vision disc , is an optical storage medium for videos in home use. Because of their high quality, LDs have also been used in the professional sector. The scanning is carried out contactless by a laser . In contrast to tapes, records, video tapes and other video disk technologies, there is no mechanical wear and tear. In contrast to video CD and DVD, the video signal was recorded in analog form. In the early days of the laser disc, the same applied to the audio signal, but in 1987 a digital one was introduced alongside the analog stereo audio track. There was also experimentation with digital soundtracks such as Dolby Digital 5.1 or DTS. As with the DVD, chapters and features could be selected directly. With a diameter of 30 cm, the laser disc was a considerable size compared to other optical media. This diameter is identical to that of a long-playing record. At the turn of the millennium, it was almost completely superseded by the DVD and is now only of importance in collectors' circles.
History of the Laserdisc
DiscoVision
The first system that used a laser beam to scan image information was developed by MCA in 1971 and presented to the public in 1972 under the name DiscoVision . However, it was not ready for the market until 1978 and was introduced on the American market.
Due to production errors in the reflective layer of the image plates, which led to the rapid appearance of "laser rot" ("rot" = "rot"), MCA and Sony carried out extensive recall campaigns. DiscoVision image disks that are still preserved today are therefore usually infected with "laser red" and can only be played back with image interference or not at all. They are therefore more likely to be considered collectibles.
LaserVision
At the same time, a system was developed by Philips and published under the name LaserVision , which was offered in Europe and the USA. The first LaserVision players were launched on May 26, 1982. In Germany the system was introduced some time later with further developed playback devices.
The uncompressed image and sound information stored in analog form was scanned with a helium-neon laser , the sound information being available in hi-fi stereo sound and stored separately from the image information.
While the format did not establish itself in the private market in Europe, it was found in 2% (1998) of US households and 10% (1999) of households in Japan due to its high quality. The LD was the first medium with exclusive special editions that included extras such as audio commentary, trailers and background reports. Often the filmmakers were asked for the LD editions or made new transfers. This basis established an industry that today helps BluRay and DVD to their success.
LaserVision interactive
Unlike in the private sector, the optical disc developed for commercial applications. The basis of this development were interactive controls (e.g. Teleselect, ILDIS), which used the possibilities of single image access in connection with a computer or a database. Pilot projects in the point-of-sales area were the “job profiles” of the Federal Labor Office and “The District of Celle”. Another area of application was education and training. The main importance of such projects was that future applications in the field of broadband communication could be anticipated and tested. This became most evident in the MEDKOM project , where an image disk changer was used as the central storage medium.
LaserDisc
Pioneer developed the LaserVision system further and in 1986 presented the successor system LaserDisc , which in NTSC format contained two digital audio tracks with 44.1 kHz in addition to the two analogue ones . In the PAL system, the analog tracks were dropped in favor of the digital ones; there was no bandwidth for all four.
In 1992 "Dolby Digital Surround" with 5.1 or 6.1 EX was introduced in the LaserDisc system. The audio information was available on one of the two audio tracks, which are normally used in analog format, as a modulated RF signal that had to be converted into a baseband signal with the help of an external demodulator before it could be forwarded to the amplifier via S / PDIF. Some mostly high-priced AV receivers had the demodulator integrated at the time and accordingly offered an RF-AC3 input, such as the Denon AVC-3800: Contrary to what is often misleading - even in specialist literature - the frequency-modulated RF signal is on both the LaserDisc digital in nature, even if present as a modulated broadband signal at the RF output. If this were not the case, a lossless reconstruction of the AC3 frames would not be possible.
"Dolby Digital Surround" was only possible with video disks recorded in NTSC format due to the "analog" sound track required. The second "analog" sound track often contained a Spanish or French language version in mono or a commentary by the director.
In 1995, "dts Digital Surround" was introduced on the digital sound track. LaserDiscs and CDs allow a data rate of 1235 kbit / s, DVDs a data rate of 754.5 or 1509.75 kbit / s. The "dts Digital Surround" sound is available with LaserDiscs in PAL and NTSC format. The technical requirement for using DTS sound is a digital sound output on the playback device. Since the sound of DTS LaserDiscs in PAL could only be heard with a DTS decoder and DTS was not yet widely used, LDs with DTS in PAL are rare. With those in NTSC, a mix in Dolby Surround was usually also placed on the analog tracks.
In 1996, with the film “ Mikrokosmos ”, PALplus was introduced as the coding method .
In the late 1990s, Pioneer launched a number of LD / VCD / CD / DVD players. They were the only players that could play DVDs and LaserDiscs. The last model that was offered in Germany was the Pioneer DVL-919E. The price at that time was around DM 2,800.
technology
In contrast to the video CD (VCD) or DVD , the video image is stored on the LD in analog form. During mastering, the video signal is modulated and pressed alternately as "depression" and "non-depression" at the zero crossings of the signal. In an LD player, a PLL synthesizer follows these wells and uses them to regenerate the original signal. Error detection and correction are principally not possible.
The picture quality is judged to be excellent despite the limitations of the PAL or NTSC color system.
LDs are available in three sizes: 30 cm (LP), 20 cm (EP) and 12 cm. The two large formats can be recorded on both sides.
The recording takes place in different rotation modes : CAV or CLV. CAV (Constant Angular Velocity) allows slow motion and still images in optimal quality, but the playing time is limited to 30 minutes (NTSC) or 36 minutes (PAL) per side. CAV discs always rotate at 1500 / min (PAL) or 1800 / min (NTSC). The CLV process was developed to accommodate feature films on the medium that can be played on both sides. CLV (Constant Linear Velocity or also called Extended Play) allows 60 minutes (NTSC) or 64 minutes (PAL) per side with the same quality. Here the disks also rotate very quickly at first, but become slower as the film progresses, as up to 3 images per revolution are stored when the reading head has moved towards the outer diameter. With CLV, slow motion and fast motion are only possible with players with a “digital frame store” (such as the Pioneer DVL-909 or -919).
The 12 cm version is often referred to as CD-Video , but has nothing to do with the DVD predecessor Video-CD . 6 minutes of picture and sound and a further 20 minutes only of sound can be recorded. An additional audio-only component can be played by any CD player. The regular video track, however, is completely incompatible with CD or DVD formats and cannot be read by the corresponding drives.
Audio process on the laser disc
In Germany only laser discs with analog sound were released until 1985. They had two audio tracks for playback in stereo or two-channel sound, and - with the appropriate coding of the audio signal - in Dolby Surround Pro Logic .
In 1986 the first records with digital sound (16-bit, 44.1 kHz - corresponding to the audio CD) came onto the market. This involved two additional audio tracks for stereo or Dolby Surround Pro Logic playback, which replaced the analog audio tracks in the case of PAL LaserDiscs, but were arranged parallel to the two analogue audio tracks in the case of NTSC LaserDiscs. Every NTSC LaserDisc with digital sound therefore also contains the analog sound tracks at the same time. Most players allow the user to switch between analog and digital sound at any time in the film - important for laser discs that e.g. B. had the actual film sound on the two digital tracks, while comments from the director on the individual scenes were stored on the analog sound tracks as bonus material; In addition, the analog tracks were mixed in a more compressed form, while the digital tracks were deliberately recorded with maximum dynamics - so you could choose according to personal taste. Bilingual versions of laser discs were theoretically possible with it, but this option was almost never used. Using all four audio tracks (two analog, two digital) even trilingual or quadrilingual LaserDiscs would have been possible, but in this case only with sound in mono, or once in stereo and twice in mono in the case of a trilingual LD.
In addition, the format also allowed the use of DTS and Dolby Digital (also known as AC-3 ). The data rate of DTS is fixed at full rate DTS (1536 kbit / s), while with the standardization of the DVD a new half rate DTS of 768 kbit / s was introduced in order to save space. With Dolby Digital, the maximum bit rate is lower than on DVDs (384 kbit / s to 448 kbit / s). A Dolby Digital soundtrack is only available on laser discs, which the NTSC - television standard match. For this purpose, the Dolby Digital coded sound was modulated onto the RF signal of the left analog channel on the NTSC laser disc (with NTSC laser discs, two analog audio channels could be retained in addition to the digital sound due to the lower video bandwidth). To convert the signal into a standard digital signal, an AC3-RF output on the LD player and an AC3-RF input on the amplifier are required for decoding. Since these inputs were only built into the very expensive top-class devices, there were (and are) special AC3-RF demodulators to buy that do this conversion (AC-3 RF to AC-3 S / PDIF). To do this, the AC3-RF output of the laser disc player is connected to the RF input of the demodulator. The demodulator is in turn connected to the amplifier via digital cable ( coaxial or TOSLINK ). Well-known manufacturers of these devices were Yamaha, Kenwood, Sony and Pioneer, today they are only available from small series manufacturers such as BDE Elektronik. Sometimes there were also external Dolby Digital decoders (such as the Yamaha DDP-1 or DDP-2) with a built-in RF signal converter. These devices with (for those times) much better AC3 decoders were also used if the decoder built into the amplifier was of inferior quality or simply only Dolby Surround was available.
There were also brief attempts to introduce laser discs with Dolby Digital sound in Germany. For this purpose, NTSC laser discs with German sound were pressed. This was technically possible because many of the players at the time were able to output both a PAL and an NTSC signal. However, the format has not caught on - only two laser discs with AC3 sound have been released in Germany ( True Lies and The Long Kiss Goodnight ).
The only German laser disc with DTS - soundtrack was Brother of Sleep , which in addition also one of three German LDs with anamorphic imaging was.
Quality compared to VHS and DVD
- resolution
- All four formats named below offer 576 visible horizontal lines in PAL format ( 480 lines for NTSC ).
- The video frequency bandwidth of 3 MHz for VHS only allows about 240 light-dark changes per image line. This results in an image with the unusual resolution ratio of around 320 × 576.
- With Super-VHS ( S-VHS ) the resolution has been increased to 533 × 576 (PAL).
- For VHS and S-VHS, however, it must be remembered that the exact horizontal position (phase position) of the possible light-dark changes is arbitrary, since the recording formats are analog. This leads to a better representation than the mere indication of the resolution might suggest.
- LD: limited to 640 × 576 pixels (PAL) by the transmission format used (PAL / NTSC)
- DVD: limited to 720 × 576 pixels (PAL) by standardized number of pixels (based on the television standard )
- Image errors
- VHS: increasingly due to wear and tear, drop-outs, shimmering colors in rich blue or red tones
- LD: large area flicker and "laser red" (decomposition of the reflective layer after approx. 10-20 years due to errors in the manufacturing process for many laser discs from some factories)
- DVD: Digital compression artifacts . These often show up with fast camera pans, recordings with extremely high levels of detail or very soft gradients ( quantization levels ).
- volume
- VHS: analog, mono (longitudinal track) or hi-fi stereo (on the helical track)
- LD: Digital, PCM , 2–4 channels, alternatively multi-channel sound
- DVD: Digital, PCM or compressed , 1–7 channels, multiple audio tracks
The cult around the laser disc
At the time of its manufacture, the laser disc was mainly used by high-end users. There were various reasons for this: For high-end users, the picture quality, superior to VHS cassettes, and the excellent sound were in the foreground. In Germany, the companies Laser Paradise and Astro in particular contributed to the spread of the medium. Both companies mainly pressed horror and splatter films onto the medium, such as Dawn of the Dead or Tanz der Teufel .
Since the laser disc was never a mass medium, it was mostly only available in large metropolises in the specialist departments of electronics stores. A few committed mail order companies such as “Frankfurt Laserdiscs” also offered them nationwide and thus ensured greater distribution.
Another provider was the Berlin company Laser-Eye-Land, which tried to promote the distribution with its own imports from Japan, USA, Hong Kong and Singapore. Special "uncut" versions of well-known action and horror films were also sold there, which were often not available on German laser discs and VHS tapes.
The Laserdisc differed from the VHS cassette in terms of sound and picture quality, especially in terms of additional material: Laserdisc contained extensive bonus material such as a making of , interviews, audio commentary , scenes that were canceled and often small magazines or other gimmicks . This is probably also the reason why many old (and new) fans still crowd around the laser disc, continue to collect it or complete their collection. Such elaborately designed laser discs were mostly released as a box in a special collector's version, which was also quite expensive. When the last German laser disc was pressed in 1999, many companies had already switched to the aspiring DVD . The laser disc has only recently become accessible to the “normal consumer” due to the massive drop in prices, and so many now remember the interest in the LD at that time.
The laser disc is interesting for newcomers today due to the "closed" collection area. There is only a manageable number of titles, for example around 1200 German or around 140 NTSC titles with DTS sound or 23 in widescreen (16: 9 or "Squeeze") or 54 releases from Astro Records and Filmworks.
various
A Hi-Vision-LD (or HD-LD / MUSE LD) was offered in Japan from 1992 . It had an even better picture quality ( HD TV with 1035i) compared to the normal LD, but did not catch on and was withdrawn from the market in 1997.
It was also possible to make your own recordings with laser disc recorders, but only in CAV mode . Devices like the Sony LVR300 cost approximately US $ 18,000. There were also special blanks in the caddy .
The laser disc became known to a wide audience through the career information centers (BIZ) of the Federal Employment Agency , where information films on laser discs ("image plates") could be viewed for many years. The 30 cm LP version was used, which was mostly played on one side.
The image plate was also used for training purposes - for example by the Bundeswehr or the former Deutsche Bundespost or Deutsche Post AG. The viewer was given the opportunity to intervene interactively in the further course and thus determine the continuing action or the following film sequences (to a limited extent) himself. At the end of the 1990s, the optical disk was retired from Deutsche Post AG in favor of the video CD . IBM used the laserdisc to train their dealers. A PC with a DOS operating system controlled an external video disk player.
The laser disc is also known to some for its use in the arcade games Dragon's Lair and Space Ace .
Between 1982 and 1999 around 1200 German-language feature films were released on Laserdisc. The last German LDs appeared in autumn 1999. There are contradicting information about the really last German-language laser disc:
- cmv-Laservision calls it: "Sado" (9/1999) two months after "The return of the zombies" (7/1999)
- laser-disc.de names: "Mike Mendez 'Killers" (Laser Paradise) and "Snow White" (Lime Pictures) (10/1999)
The world's last LaserDisc was made in Japan in 2001. The title is called "Tokyo Raiders" and was released on September 21, 2001.
The release of Star Wars: Episode I on Laserdisc in Japan was the only version of this film available in Dolby-Digital 5.1 EX until the normal DVD version was released.
In the movie " Back to the Future II ", in the scene in which Marty and Doc Brown want to put Jennifer down in a side street in the future , you can see a large amount of laser discs in the background, which apparently need to be disposed of.
See also
- SVCD
- Optical storage
- Computer output on laser disk
- DAPHNE (emulator)
Individual evidence
- ↑ Kristine R. Brancolini: New and Emerging Video Technologies: A Status Report. (No longer available online.) In: Wisconsin Library Association. October 29, 1998, archived from the original on October 15, 2007 ; accessed on February 21, 2008 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Julie Flaherty: Bittersweet Times for Collectors of Laser Disk Movies. In: The New York Times. April 29, 1999, accessed February 21, 2008 .
- ↑ Archived copy ( Memento of the original from September 10, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Chapter 7 Making Digital Audio a Reality. Retrieved November 17, 2016 .
- ↑ Back of the Denon AVC-3800. (No longer available online.) Archived from the original on September 24, 2015 ; Retrieved February 7, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Back to the future - When yesterday was today still tomorrow . In: MobileGeeks Germany . October 21, 2015 ( mobilegeeks.de [accessed March 9, 2017]).
Web links
- laserdisc.holin.de - Some facts about the laserdisc
- laserdiscarchive.co.uk List of almost all LD players ever produced with technical data, operating instructions and photographs (English)
