Video Home System
| Video Home System | |
|---|---|
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| Bandwidth: | ½ ″ (1.27 cm) |
| Colour: | Subcarrier |
| Volume: | Longitudinal track,
HiFi on a helical track |
| Running time: | SP: 0.5-5 hours (PAL)
0.5-3.5 hours (NTSC). Double / triple Run length with LP / SLP. |
| Introduction: | 1976 |
VHS is an analog recording and playback system for video recorders developed by JVC and first launched in Japan in 1976 . VHS established itself as the standard for private video magnetic tape recordings and was not replaced by a digital system ( DVD ) until 1995, despite the development of better analog systems . In contrast to many competing systems, VHS uses a so-called "M" loading mechanism, which requires two video heads for continuous signal transmission, but allows more compact devices.
Meaning "VHS"
Video Home System was the official name for VHS from the start (see web link).
Some believe that the official reading Video Home System is a backronym and that the abbreviation originally stood for Vertical Helical Scan , the recording method used on magnetic tape. However, this is questionable, since in addition to the 2- inch - quadruplex system all analog formats with helical scanning work. According to other reports, VHS stood for Victor Helical Scan ; JVC (Victor Company of Japan) is simply called Victor within Japan .
Cassettes
A VHS cassette contains a long magnetic tape that is wound from one reel to another when played in the video recorder. It runs slowly past the fast rotating head drum of the video recorder. The cassettes can be protected (with most brands sold as empty cassettes) by breaking out a tab on the rear long side to prevent the recordings from being deleted. Re-recording is then possible by covering with a piece of adhesive tape.
VHS tapes are one-sided, so they cannot be inserted upside down. When viewing the recording, there is no need to turn the cassette in the middle of the playing time; it must be rewound before the next use. Newer video recorders often offer a very high winding speed. However, the speed of the fast picture search is limited for technical reasons: it strains the mechanics and the magnetic tape and, for technical reasons, is only possible with VHS with picture disturbances that would completely cover the actual picture content at too high a speed.
The magnetic tape of the VHS cassette is not freely accessible, but protected by a flap. It is only opened in the recorder and the mechanism pulls out enough tape that half of the video drum can be wrapped around. The door can also be opened by pressing the small rectangular latch near the door hinge on the right side of the cassette with your finger. You unlock the locking mechanism of the flap and have a clear view of the magnetic tape after it has been folded up.
While z. For example, with audio cassettes, the end of the tape is usually recognized by the device simply by the fact that the reels can no longer turn, this is not possible with video systems with a head drum: the thin magnetic tape would become too tight around the fast rotating one when rewinding to the physical end of the tape Lay the drum with the heads protruding slightly, and the tape and heads would be damaged. This is why transparent plastic tape is used for the ends of the tape in VHS cassettes: A small light source ( lamp or LED ) built into the recorder fits into the front center opening on the underside of the cassette and constantly illuminates the tape from the inside. When the flap is open, openings are exposed on the two narrow sides of the cassette, in front of which there are light sensors (e.g. phototransistors ) in the device . If the end of the tape is near, the light can fall through the transparent tape onto the sensor and the playback or winding process is stopped immediately.
Furthermore have VHS tapes a lock mechanism that prevents the rotation of the reels when the cassette is not loaded in the machine, which Bandsalat is prevented. The lock is released in the device by inserting a pin into the rear central opening of the cassette and lifting the locking lever off the tape reels.
Technical specifications
VHS stores each field in its own helical track on the tape. The full screen method is not supported. Modern devices with hi-fi stereo can record analog encoded Dolby Surround signals.
Recorders that work with the NTSC television standard use a significantly higher tape speed in normal recording mode than PAL and SECAM devices. All empty cassettes can be used in all recorders, but the running time indicated on the cassettes is no longer correct. To distinguish between the formats T- (minutes) for NTSC (for example T-120) and E- (minutes) for PAL (for example E-180). The reduced tape speed on PAL recorders is a result of the technical progress that became available after the development of the NTSC VHS specifications.
The common VHS cassettes for PAL usually have a running time of around two to four hours and are marked with E- (for PAL / SECAM) and the playing time in minutes based on the standard play mode (SP). The actual time is often a few minutes longer. Empty cassettes with a running time of less than two hours (E-30, E-60 and E-90) are sometimes more expensive than longer ones due to the number of pieces, especially with commercially recorded cassettes, there are also various special lengths. With cassettes for NTSC, the usual running time is only one and a half to three hours.
On many devices, the beginning of a recording is marked by an index signal, which allows easy access to a specific point on the tape later. With some devices, these markings can be inserted at any point during the recording or removed again later.
In English-speaking countries, when feature films were released on VHS, “ Pan & Scan ” was common, in which a considerable part of the image content is lost on the left and right. This was widespread in German-speaking countries until the early 1990s, after which letterbox with the familiar black bars above and below was often used. Since the picture resolution of conventional American (NTSC) tube televisions is significantly worse both vertically (because of the lower number of lines) and horizontally (because of the lower bandwidth) than with European (PAL) sets, the letterbox format would only be problematic in the USA Loss of picture quality was possible and its use on VHS tapes was therefore not common there.
An anamorphic 16: 9 picture format is possible, but it is unusual, especially with commercially recorded cassettes, because of the incompatibility with the 4: 3 format (on televisions without 16: 9 switchover). If anamorphic programs are recorded with VHS, the corresponding televisions can evaluate the widescreen signal and automatically switch to 16: 9.
Recording details
The magnetic tape is 12.7 mm (half-inch) wide and moves at just a few centimeters per second (PAL: 2.339 cm / s, NTSC: 3.335 cm / s). For recording and playback, the tape runs in a semicircle around a slightly inclined drum with a diameter of 62 mm. The drum has two opposing read / write heads that are used alternately; the head with tape contact is always active. Due to the inclined mounting of the drum, the heads run diagonally across the belt and sweep it diagonally from top to bottom.
The analog TV signal, which has a bandwidth of around 4.8 to 5.5 MHz depending on the country, is separated into brightness and color signals by the video recorder, the brightness information is limited to 3 MHz with a low pass. A carrier signal is frequency-modulated with the brightness signal and then stored on tape. The frequency modulation enables a comparatively low susceptibility to interference in the recording, since the amplitude of the signal can be maximally amplified and limited. The carrier for the brightness signal (Y signal) is between 3.8 MHz for black (ultra black sync pulse) and 4.8 MHz for white. The two sidebands are limited to a range of 1–8 MHz.
The FM carrier frequency was chosen so that there is still space in the lower frequency range. There the color (chroma signal) is stored with a maximum bandwidth of 500 kHz using the color subcarrier reduced to 627 kHz. The human eye has a significantly reduced resolution for colors. Since the color signal is not recorded with frequency modulation but with amplitude modulation , it is particularly sensitive to noise. The process of storing the color information below the picture signal is called the color-under process and has made affordable color video recorders for home use possible by greatly reducing the requirements for exact compliance with tape and drum speeds.
The auxiliary oscillator (5.06 MHz) for mixing up or down mixing the color signal during recording or playback is coupled to the head wheel servo and thus to the tape-to-head speed. This avoids color errors caused by fluctuations in tape travel. In addition, the downmixed color subcarrier is rotated 90 ° in phase during each line, so that crosstalk of the color signal between two adjacent lines or tracks is prevented (this is independent of the 180 ° phase shift inherent in the PAL television standard).
In order to achieve the required tape-to-head speed for recording, the video head drum of a PAL recorder rotates at 25 revolutions per second (NTSC: 30 revolutions per second), so that a total of 50 or 60 fields of the two heads are scanned per second - each helical track corresponds to a field, the switching between the heads takes place at the beginning of the vertical blanking interval , so that the resulting short picture disturbance cannot be seen on the screen. The relative speed between the rotating head and the tape is a few meters per second. (PAL: 4.867 m / s, NTSC: 6.953 m / s.) With PAL-VHS, 208 parallel video tracks (length: 9.734 cm, width: 0.049 mm) are written diagonally on the tape.
At the two edges of the tape there are still two longitudinal tracks that are recorded and played back by non-rotating magnetic heads at a precisely defined distance behind the head drum. One of these tracks contains pulses that show the recorder the exact position of the helical tracks so that it does not try to read between two helical tracks during playback, which would lead to severe picture disturbances. The other track records the sound. Since the tape runs slower than an audio cassette , the sound quality of this so-called linear tone is quite limited, and almost all recorders on this track only work in mono. With newer recorders, the sound is therefore also written to the helical tracks or read from there. For this purpose, there are two more heads on the head drum. This so-called hi-fi sound has a much higher quality. Hifi VHS recorders also record the sound in the longitudinal track for compatibility with conventional devices.
Longplay and super longplay
Many devices have a long-play mode (LP), in which the running time is doubled by reducing the tape speed and thus also the quality (this can be particularly evident in the image search and the quality of the linear sound track). B. 10-hour recordings possible with an E-300 cassette. When playing such recordings on VHS devices without LP mode, they are played back with strong interference and sometimes at twice the speed. More rarely, there is also an extended play mode (EP) or super long play mode (SLP), which enable even longer runtimes.
In the NTSC area, the super long play mode (SLP) with a third tape speed to extend the recording time is standard. Only a few recorders offer halved tape speed there. The final tape speed of NTSC-SLP and PAL-LP is almost the same.
| PAL SP | PAL LP | NTSC SP | NTSC LP | NTSC EP / SLP |
|---|---|---|---|---|
| 2,339 | 1.170 | 3.335 | 1,668 | 1,112 |
Although the reduced tape speed noticeably affects the quality of the recording, even with cassettes with a high-grade coating, it was often used in view of the initially high cassette prices. In order to be able to record very long programs in one go, LP was also required later.
Usual VHS tape lengths and playing times
| Tape lettering |
Tape length |
Playing time (PAL) | Play time (NTSC) | |||
|---|---|---|---|---|---|---|
| SP | LP | SP | LP | EP / SLP | ||
| PAL market | ||||||
| E-30 (VHS-C) | 45 m | 30 min | 1 h | 22.5 min | 45 min | 1 h 8 min |
| E-120 | 175 m | 2 h | 4 h | 1 h 26 min | 2 h 52 min | 4 h 18 min |
| E-180 | 259 m | 3 h | 6 h | 2 h 9 min | 4 h 18 min | 6 h 27 min |
| E-240 | 348 m | 4 h | 8 h | 2 h 53 min | 5 h 46 min | 8 h 39 min |
| E-300 | 435 m | 5 h | 10 h | 3 h 36 min | 7 h 20 min | 10 h 49 min |
| NTSC market | ||||||
| T-30 (VHS-C) | 63 m | 45 min | 1 h 30 min | 30 min | 1 h | 1 h 30 min |
| T-120 | 248 m | 2 h 49 min | 5 h 38 min | 2 h | 4 h | 6 h |
| T-160 | 328 m | 3 h 43 min | 7 h 26 min | 2 h 40 min | 5 h 20 min | 8 h |
| T-180 | 369 m | 4 h 13 min | 8 h 27 min | 3 h | 6 h | 9 h |
The E-300 cassettes use a particularly thin carrier material in order to be able to wind the more than 430 meters of tape onto the cassette spools. At around 430 meters, the VHS cassette was considered exhausted for a long time. However, when using D-VHS DF-480 cartridges, SP can run for 5 hours and 45 minutes.
While conventional DVD recorders (with single-layer media) usually only offer 1, 2, 4 or 6 hours of total playing time, depending on the quality, a PAL-VHS recorder can record up to 5 hours, in LP mode up to 10 hours continuously.
Image resolution
Since the TV signal is recorded directly (without intermediate storage), all lines (including those without image content) must be taken into account, that is 625 lines per frame for PAL and 525 lines for NTSC. The vertical picture resolution is 485 lines for NTSC frames and 576 lines for PAL. In the horizontal direction, the resolution is 220–240 lines. Since this is calculated on the level of the image and VHS was developed for 4: 3 formats, the actual brightness resolution per scanline is a maximum of around 280-300 pieces of information (i.e. around 160 oscillations per scanline.)
Due to the system, the image resolution (the brightness information) of VHS is limited - vertically by the underlying television standard with its fixed number of lines, horizontally by the selected FM carrier frequency. This is independent of the quality of the device or the magnetic tapes used. As a result, thin vertical lines in the image are only shown blurred, which is clearly noticeable in negative ways when displaying human hair (hair looks greasy). At hard contrasts (e.g. white to black) you can often see a thick line in between on VHS recordings (in this case gray.) Slightly higher frequencies are only saved with a weak amplitude.
The complete field (with all lines) is recorded in a single track. During recording and playback, the synchronization with the beginning of the line (H-Sync) is often not exact, so that a slight "line wobble" can be observed (especially in LP mode). A so-called Time Base Corrector can help in the professional field .
Since the color carrier is reduced for magnetic recording and the color signal can only be stored in the bandwidth that is still available in quadrature amplitude modulation (and not frequency modulated), it is subject to strong noise influences.
Color is recorded with a significantly reduced resolution. Only about 30-40 different color values are saved per line. VHS also uses a system for color noise reduction in which the color values of several lines are averaged, so that the vertical color resolution is also significantly reduced. Despite the noise reduction, image areas with high color saturation flicker violently. Another consequence of the color noise reduction is the "bleeding" of the color in the case of multiple video copies - the color signal comes out of the device later than when it was recorded, which means that the color areas slide noticeably downwards in the image compared to the brightness values when copied several times . This makes VHS unsuitable for ( semi- ) professional purposes, but offers a good compromise for home use in order to minimize color flicker.
Audio quality
The standard audio track is a mono signal recorded linearly at the lower edge of the tape (similar to audio cassettes) with a maximum bandwidth of 10 kHz and a signal-to-noise ratio of only about 40 dB. Later devices sometimes saved two separate channels (i.e. stereo) instead of the mono track. Some very high-quality devices were also equipped with the Dolby B noise reduction system.
Finally, in the mid-1980s, the hi-fi stereo sound process was developed, in which the audio signal is also written in the oblique video tracks, making linear stereo recording obsolete. For reasons of compatibility, the mono track is also retained with hi-fi stereo recorders. The (analog) hi-fi stereo sound is frequency-modulated with a separate pair of heads written “into the depth” of the magnetic layer, while the video signal only magnetizes the surface. The audio track contains the left channel on a 1.4 MHz carrier and the right channel on a 1.8 MHz carrier. This means that audio and video frequencies overlap. In order to achieve the best possible separation of the two signals, the angles of the narrow openings of the audio heads are slightly offset compared to the video heads.
HiFi VHS recorders offer a sound quality that comes very close to the CD , which is why such devices were sometimes used for purposes other than those intended as audio recorders, especially in the early days. Some recorders even offered their own hi-fi audio mode, in which only the pure audio signal was recorded and the video heads were switched off in order to avoid impairment of the sound quality due to the video signal, which in this case was unused (and therefore mostly black). Up until the mid-1990s, almost all hi-fi VHS recorders also had manual audio control.
Devices with hi-fi stereo sound achieve a bandwidth of 20 Hz to 20 kHz with a signal-to-noise ratio of around 75 dB . The disadvantage is that, due to switching between the two rotating heads, there is sometimes interference in the form of a crackling noise at 50 Hz. This problem occurs particularly when playing on a device other than the recording device. In addition, with older tapes, this audio information first becomes illegible before image disturbances occur as the age progresses.
Number of heads
Since the drum is only wrapped around half of the magnetic tape, at least two heads at a theoretically 180 ° angle are required to continuously read (or write) the tape: one for the odd-numbered, the other for the even-numbered TV lines. The video tracks written by the heads are close together. Due to the field method, however, the synchronizing signal of a line in the first field would now be in the range of the image signal of a line of the next field. To prevent this, the heads of the VHS signal are at an angle of approx. 179 ° to each other. This means that each field begins at an alternating position. Image and sync signals are each at the same position on two adjacent tracks in the fields and cannot interfere with one another.
Sometimes recorders with three heads were offered. The third head only served to enable an interference-free still image.
In longplay mode, the tape moves at half SP speed, which results in a track image with video tracks that are only half as wide. Recorders with a long play function therefore have two additional, narrower video heads. At the same time, the additional long-play heads are also used for the interference-free still image and for the image search in SP mode.
Two additional heads are provided for hi-fi stereo, on the one hand to realize the different angle (azimuth) of the head gap opening (for the audio / video signal separation) and on the other hand to write the sound on the magnetic tape shortly before the video signal . Usually, hi-fi stereo devices are also equipped with the longplay function, so that they then have 6 heads.
Some very high quality VHS recorders are also equipped with a seventh head. This is a rotating erase head that enables scenes to be seamlessly inserted into existing recordings ("insert cut").
In addition to the rotating head drum, every VHS recorder has a fixed full-track erase head and a so-called combination head. This consists of an audio read / write head, audio track erase head and sync head. He is responsible for the longitudinal track and the synchronous track. With the latter, the heads of the drum are synchronized to the tracks recorded at an angle on the tape during playback (English tracking). In devices with an auto-tracking function, the electronics automatically set the optimal tracking by slightly adjusting this control loop and measuring the video or audio playback level.
Device connections
Most VHS recorders have a TV tuner so that they can record even when the television is switched off (or another television channel selection), and accordingly offer an analog TV connection that connects to the antenna of analog terrestrial television or the socket of analog cable television is connected. To avoid the need for an external antenna distributor , the recorders also have an antenna output so that the signal can be looped through the recorder to the television. In addition to the antenna or cable signal that is passed through, the antenna output also offers an HF -modulated version of the image and sound signal generated by the recorder itself, which initially represented the usual way of forwarding the played image to the television, as television up to the middle of the 1980s rarely had other signal inputs than the antenna connection. NTSC devices usually “transmit” on one of two switch-selectable channels in the VHF range (often channels 2 and 3), PAL devices mostly in the UHF range (earlier often channel 36, which was reserved for such purposes, in newer ones Devices sometimes use a very high-frequency channel such as channel 68 or 69).
For output to the television, however, the SCART connection became established in European devices from 1984 onwards, in some cases in addition to a standard composite / sound connection (for stereo devices with three plugs: video, audio left, audio right ) is available. With NTSC devices, on the other hand, the composite connection prevailed, SCART is extremely uncommon in the NTSC area. Both the SCART and the composite connection offer an unmodulated baseband video signal and thus a significantly better picture quality than the antenna output, provided that the television has the appropriate input sockets in addition to the antenna connection. In order to be able to record directly from another device, most devices also offer a composite video and an audio input (if a SCART socket is available, integrated into this).
In addition to the composite signal, SCART can also transmit an even higher quality RGB signal and, in a newer version, an S-video signal, but this option is not used with VHS video recorders because a composite signal has the maximum possible image quality of VHS already fully exhausted.
Cassette prices
At the end of the 1970s, shortly after the system came onto the market in Germany, an E-180 cassette cost around 45 to 55 DM (around 58 to 71 euros in today's currency). At the turn of the millennium, the price for cassettes with a playing time of two to four hours was around 1.50 euros. Even five-hour tapes were available for around 3 euros. Cassettes with a playing time of less than two hours (e.g. E-30, E-60 and E-90) were considerably more expensive and could cost well over 5 euros per tape. In the meantime (2016) the prices have risen again significantly due to the increasingly limited distribution of VHS cassettes and the discontinuation of production. Cassettes with a playing time of 240 minutes are usually no longer available for less than 5 euros. Since production has ceased, prices for unused cartridges are likely to continue to rise, but it can be assumed that the quality of the remaining stocks will decline due to aging and / or improper storage.
Versions of VHS
There are now some improved versions of the VHS standard. So-called VHS-HQ devices, on the market from around 1985, offer a slightly improved picture quality compared to the traditional VHS recorders. The HQ method is upwardly and completely downwardly compatible to a limited extent: HQ recordings also look a little better on devices without HQ, conversely, tapes that were recorded with the old VHS devices appear even more dull and blurred when played on HQ devices than the VHS standard technically allows. Today, specifications comparable to VHS-HQ are standard for all VHS recorders.
The S-VHS system, introduced in 1987, is a further developed VHS standard which, by choosing a higher FM carrier frequency and using high-quality tape material, offers around 60% more horizontal image resolution and can therefore store the brightness signal in practically full resolution. S-VHS did not achieve any resounding market success, but was able to establish itself as one of the alternatives with superior quality to the VHS system. VHS videos can be played on S-VHS machines. The reverse does not apply, only a few (and then specially marked) VHS devices can play S-VHS videos, but only in VHS quality. In the Professional S system variant , semi-professional S-VHS devices were also produced, which are compatible with the normal S-VHS standard and VHS. S-VHS recorders often offer an S-Video input and output, as the composite signal common in the VHS sector no longer completely covers the image quality that can be achieved with S-VHS. This fact has led to a confusion between S-VHS (a recording format) and S-Video (a signal transmission standard).
The M-Format (from M-Loading , later further developed to the M-II-Format using metal tapes ) is a professional video system for analog component recording of the very highest image quality. It uses cassettes in two different sizes; the large cassettes correspond to the VHS design, but contain a higher quality tape, and the cassette housing has been designed differently for the purpose of clear visual differentiation. Apart from the identical cassette design, the system is in no way compatible with VHS.
The development of the M format from VHS can be compared with the emergence of the Betacam format from Betamax . With a greatly reduced tape running time, you can achieve a comprehensive increase in image quality with parameters at TV studio level. The M and M-II format were also intended for studio applications, but were only able to prevail against the worldwide distribution of Betacam and Betacam SP in a few countries, so the system was the standard at Austrian ORF for a long time . Today, the M format is no longer important, the M-II format was occasionally used in the industrial video sector until 2000.
W-VHS was an analog format for recording HDTV broadcasts that was introduced in 1994. This system could not establish itself either, only a very small number of devices were produced, which were only available for a short time in the USA and Japan.
D-VHS is a digital format based on S-VHS cassettes which supports HDTV recordings in addition to SDTV . D-VHS recorders can also record and play back cassettes in the traditional analog VHS format.
D-9 is a further digital variant of VHS from system developer JVC, based on D-VHS (but not compatible due to completely different recording formats), with image quality at the highest level. D-9 is qualitatively in the range of Digital Betacam and supports four digital audio tracks in uncompressed DAT audio quality.
Under the system name Alesis Digital Audio Tape, there is another format derived from the VHS system, a digital multi-track audio recording system, the so-called ADAT from Alesis. Using a modified, high-quality VHS tape drive and the S-VHS video cassette, it records eight-channel PCM audio signals in DAT sound quality. A recording of image information by ADAT, however, is not intended.
For use in home video, only the normal VHS was practically relevant. The improvements - with the exception of HQ and the hi-fi stereo capability, which have since become standard in VHS recorders - did not find lasting dissemination and became obsolete with the introduction of HDD / DVD recorders.
Compact cassettes
VHS-C is a version of the VHS format with smaller cassettes, but with an identical track image and the same technical parameters. These mini-cassettes were specially designed for camcorders and, thanks to their playability using adapters, found enormous popularity in every conventional VHS video device. There is also such a mini version of S-VHS , called S-VHS-C .
history
First launched in Japan in 1976 as a pure NTSC system, VHS became the standard in home video in Europe in 1980 after it had prevailed on the market against Sony's Betamax and VCR / Video 2000 from Grundig and Philips. Interestingly, the VHS development is based on a Sony patent acquired by JVC. One of the main reasons for the success was the license fees demanded by the system inventors of the other formats, while JVC made the licensing much more generous than the competition. That led to the format war .
From the beginning, VHS was consistently developed with the private user in mind and offered comparatively inexpensive, reliable and simply constructed devices. This is often seen as the decisive point through which VHS was able to win large market shares despite its lower picture quality. The maximum running time of the cassettes was also initially higher with VHS than with Betamax; a very strong argument in favor of VHS for the American market, as it made it possible to record a complete football game on a cassette.
Another aspect underestimated by Sony's VHS competitor Betamax was the power of the porn industry . While Sony (and thus Betamax) turned its back on this, the first pornographic film appeared on VHS. Shortly afterwards, the first video stores opened that exclusively offered pornographic material on VHS cassettes.
There is the Japanese documentary "Hi wa Mata Noboru" about the emergence of VHS (especially the secret development and the resistance against the Japanese Ministry of Commerce) and the reasons for the success in Japan against Sony's Betamax, in English "Dawn of a New Day: The Man Behind VHS ”.
After VHS had been the market-leading home video system for around twenty years, it was gradually replaced by digital DVD from around 2000 . Sales of VHS devices have declined particularly since DVD devices with a recording function existed. From around 2002, more DVD than VHS videos were sold. The last Hollywood film to appear on VHS was A History of Violence in 2006 . On October 28, 2008, JVC announced the discontinuation of production of devices of this format. The last major manufacturer of VHS cassettes, Distribution Video & Audio Inc., announced on December 22, 2008 that production would end for the end of the year. At the end of July 2016, the last remaining manufacturer of VHS recorders worldwide - Funai Electric - ceased their production. In 2015 he had sold 750,000 units. VHS tapes are still commercially available; the Japanese manufacturer TDK is still producing these for the German market (as of September 24, 2016).
| year | EST | DVDs | Blu-ray discs | HD DVDs | VHS tapes | |
|---|---|---|---|---|---|---|
| 1999 | k. A. | 2,100,000 | - | - | 39,800,000 | |
| 2000 | k. A. | 8,200,000 | - | - | 35,800,000 | |
| 2001 | k. A. | 18,900,000 | - | - | 31,700,000 | |
| 2002 | k. A. | 35,500,000 | - | - | 28,600,000 | |
| 2003 | k. A. | 64,100,000 | - | - | 20,800,000 | |
| 2004 | k. A. | 90,200,000 | - | - | 13,000,000 | |
| 2005 | k. A. | 98,700,000 | - | - | 5,600,000 | |
| 2006 | k. A. | 100,800,000 | - | - | 2,000,000 | |
| 2007 | k. A. | 103,300,000 | 372,000 | 130,000 | 800,000 | |
| 2008 | k. A. | 101,300,000 | 1,700,000 | 500,000 | 200,000 | |
| 2009 | 1,000,000 | 106,600,000 | 6,200,000 | 100,000 (HD-DVD + VHS) | ||
| 2010 | 2,900,000 | 103,400,000 | 12,000,000 | k. A. | k. A. | |
| 2011 | 4,200,000 | 101,200,000 | 17,200,000 | k. A. | k. A. | |
| 2012 | 4,900,000 | 89,400,000 | 23,100,000 | k. A. | k. A. | |
| 2013 | 5,200,000 | 87,800,000 | 29,300,000 | k. A. | k. A. | |
| 2014 | 5,900,000 | 76,900,000 | 27,900,000 | k. A. | k. A. | |
| 2015 | 9,200,000 | 71,500,000 | 28,800,000 | k. A. | k. A. | |
| 2016 | 12,500,000 | 60,400,000 | 26,300,000 | k. A. | k. A. | |
| 2017 | 15,800,000 | 53,000,000 | 26,200,000 | k. A. | k. A. | |
Source: Bundesverband Audiovisuelle Medien e. V.
copy protection
The VHS standard was redefined by the developer and rights holder JVC in 1985 under pressure from the film industry (and improved or worsened depending on the point of view). VHS licensees were only allowed to build video recorders with Automatic Gain Control (AGC) whose control time constant was not allowed to exceed a defined maximum. Originally intended to improve the image signal on the receiving side through automatic control, this technology could be used to implement the analog copy protection ( Macrovision ) developed by the Macrovision Corporation . A small part of the commercial video cassettes produced in the film industry's copy plants, a larger part of the video store rental cassettes, which is dependent on the respective manufacturer or rental company, contains the macrovision signal, which confuses the AGC of the receiving video recorder. The AGC is stimulated by changing light-dark signals in the blanking interval to continuously readjust the brightness. The result is unusable copies of rental or purchase video cassettes provided with macrovision due to strong fluctuations in brightness and color saturation.
Simply playing Macrovision cassettes from the video recorder to the television works without interference, as the latter builds the entire return signal itself through generators and its AGC has a longer time constant and is therefore hardly influenced by the interference. From the point of view of the film industry, so-called black copies have been made more difficult; from the point of view of the consumer, the otherwise generally permissible production of private copies - even of backup copies of cassettes once purchased - has been made more difficult or even impossible. Removing the interfering signals is technically quite simple, but the sale of corresponding additional devices was banned in most EU countries around 2003. Building it yourself is no problem for a reasonably experienced electronics technician. Such "copy amplifiers" can still be found on eBay too. A very simple option was often to use a second SCART connection on the television itself. This simply looped through the now MV-free signal. However, some devices, especially higher quality ones, output the video signal including MV via the SCART output.
Another possibility was to loop the HF signal output by the video recorder through a second Betamax or Video 2000 recorder. This also filtered out the macrovision signal.
See also
Individual evidence
- ↑ spiegel.de from September 15, 2015, What happened to the DVD? , accessed on May 19, 2020.
- ↑ https://www.heise.de/newsticker/meldung/Die-Letzt-ihrer-Art-VHS-Cassetten-haben-nicht-mehr-her alten- 2733692.html
- ↑ Never rewind: New technology replaces the VHS cassette on chip.de.
- ↑ Virtual Reality: Closer . In: ZEIT ONLINE . ( zeit.de [accessed on August 13, 2018]).
- ↑ Farewell, VHS! - Last delivery of VHS cassettes. Georg Wieselsberger, January 5, 2009, accessed June 5, 2016 .
- ↑ Geoff Boucher: VHS era is winding down: The last big supplier of the tapes is ditching the format, ending the long fade-out of a product that is used in the home theater . In: Los Angeles Times , December 22, 2008 (English)
- ↑ Martin Holland: The last Japanese manufacturer of VHS video recorders ceases production. In: heise online. July 21, 2016. Retrieved July 21, 2016 .
- ↑ No more tape clutter: Funai's last VHS recorder rolls off the tape . Rheinische Post , July 29, 2016, accessed on July 30, 2016
- ↑ Blu-ray - Sales Quadrupled. John Mc Donald, February 8, 2010, accessed June 5, 2016 .
Web links
- oldradio.de Technical description of the VHS magnetic tape recording (PDF; 1.69 MB)