Video 2000
| Video 2000 | |
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| Bandwidth: | ½ inch (2 × ¼ inch) |
| Colour: | depreciated color |
| Volume: | Longitudinal track (stereo) |
| Running time: | 1–4.5 hours (per side)
2–9 hours (long play; per side) |
| Introduction: | 1979 |
Video 2000 is a system for the analogue recording of color video in PAL - with some models also SECAM - on magnetic tape. It was developed by Grundig and Philips and launched in 1979 as the successor to the VCR system introduced by both companies in 1971 .
history
The Video 2000 system was presented at the International Radio Exhibition in Berlin in 1979 and met with great interest from experts. Video 2000 was a further development of the VCR system , but used a completely newly developed cassette with tape reels arranged next to one another.
VCR had given the designers the opportunity to test numerous techniques for increasing capacity (factor 1: 4). Video 2000 completed this work with a running time of up to 18 hours. The VCR designation was also retained on some Philips Video 2000 recorders. In 1985 Grundig stopped the further development and production of Video 2000 devices in favor of VHS recorders.
Initial problems at Grundig and Philips
Video 2000 was intended as the European answer to VHS from the Japanese Victor group (brand name JVC ) and Sony's Betamax , but it could not hold its own against the competition in the market. Although it was superior in terms of the technical equipment, its introduction was not initially under a good star: The first devices from Grundig and Philips worked unreliably; In addition, all Grundig recorders (with three-digit model names) showed a high failure rate after a short time due to the thin-walled plastic connectors between the drive and the motor connection board, which only occurred in the later models on the market from autumn 1983 (with four-digit model numbers ) has been repaired.
In addition, there were initially certain compatibility problems when exchanging tapes, allegedly even with lip-synchronicity, if cassettes that were recorded with Philips devices were to be played on Grundig machines. The background here is the independent development and manufacture of the drives at Grundig and Philips. The Grundig drives in all three generations had a U-Loading system, comparable to the Betamax recorders from Sony, which was, however, designed to be quite cost-effective. The first generation of Philips drives was equipped with a U-shaped tape path (erase / audio heads at the beginning and end of the "U" behind the head drum), but had an M-Load system with a cable drive and quite long transport paths. After threading, the deflection bolts were even locked in the end position by a complex mechanism. The drive was a massive component that was very complex to produce and, despite its complexity, relatively unsusceptible. The accuracy with regard to the technical parameters was better than Grundig thanks to the use of a high-precision functional group consisting of a head drum, capstan, audio / erase heads and the respective drive motors with the common base plate. In technical jargon, this type of construction of the functional group was also referred to as the “micro-world”.
Generation change improvements
However, from the second generation, or at the latest the third generation, all Grundig drives complied with the technical parameters for compatibility through appropriate detailed work. Compared to the VHS competition, however, the production costs were also a major problem with Video 2000. That's why Philips developed a completely new drive for the second generation based on the M-Load process with direct tape deflection next to the head drum and corresponding erase / audio heads next to it, as with VHS. This drive was built very compact, but still had 5 separate direct drive motors (head drum, capstan, two tape platter and a thread and cassette compartment motor) with very high quality and very short response times compared to VHS. Even the tape transport during picture search such as forward, reverse, freeze frame, slow motion, etc. was possible purely electronically via the respective direct drive motors without mechanical brakes and intervention of the thread motor to change the drive, as with VHS or Beta, and corresponded more to professional studio drives. The strip tension was also electronically controlled as in the first generation, but without a separate optoelectronic strip tension sensor. Interestingly, the Grundig technology (already in the first Grundig generation) was used here, in which the respective torque and thus the tape tension were calculated by evaluating the belt platter speeds and the power consumption of the two winding motors, a quality that even with the most expensive VHS and beta devices could never be achieved.
However, these last Philips drives were quite expensive to service due to their compactness, e.g. B. cleaning. Defects in the drive mechanism are extremely rare to this day, with the exception of the rubber pressure roller, which is easy to change. The drive was even converted into a VHS drive for a short time after Philips and Grundig decided to offer both systems on the market in parallel. This is also interesting because, up to now, the best VHS drives have been produced with it, before the simple VHS drives were switched to because of the continued high production costs. The same applies to the Grundig drives, which, as with Video 2000, always suffered from a certain vulnerability due to the belt-driven capstan drive. The achieved quality of the devices was therefore not the decisive point in the system war on VHS, but rather the high costs for the accuracy of the drive, the DTF and the respective control electronics.
In addition, the VHS developer JVC's market policy of issuing licenses for the production of VHS devices and empty cassettes proved to be more assertive than the late introduction of another video system. Grundig and Philips themselves therefore also offered VHS devices from autumn 1984, which were also very good devices because of the relationship to the Video 2000 drives already mentioned. Another unconfirmed reason for the demise of the Video 2000 system is Philips' refusal to publish pornographic content on Video 2000. Production of new devices was discontinued in 1986, the Grundig electronic division , which is geared towards professional customers, continued to sell new devices until 1988.
Before Video 2000 was discontinued, Grundig was already developing devices which enabled the cassettes to be played on both sides without turning them around (model: Video 2x4 Stereo / 2400 Reverse) and which offered the recording of hi-fi sound in helical track recording or PCM sound . However, these devices were no longer put on the market. The Video 2000 cassettes had recesses on the back for the detection of future further developments of systems with an increased number of lines (similar to S-VHS) or digital recording (similar to D-VHS).
A characteristic and unique selling point of the system was that the cassettes, like the audio cassettes , could be turned over and thus eight hours of film on one tape, or even 16 hours with the long-play devices available on the market from autumn 1984. In order to be able to find a certain part of the tape more easily even in long play mode, the Grundig models had a target run function, which was already known as Go-To from the first Philips recorders . In addition, the rewinding speeds for a correct display of the playing time and the image search speeds for good image quality have been automatically adjusted in longplay mode.
Brief technical overview
- Television standard: 625/50 black and white and color, PAL or SECAM
- Tape: ½ inch (two ¼ inch tracks)
- Head drum diameter: 65 mm
- Head drum speed: 1500 / min
- Video track width: SP = 22.5 µm / LP = 11.25 µm
- Video head gap width: 0.28 µm
- Azimuth angle of the two heads: ± 15 °
- Toe angle: 2 ° 38'51 "
- Belt speed : SP = 2,442 cm / s / LP = 1,221 cm / s
- Relative speed: SP = 5.08 m / s / LP = 5.09 m / s
- Field track length: 102 mm
- Synchronous track width: not required due to DTF, but intended as a so-called cue track with 0.3 mm for later applications
- Cassette dimensions (L × W × H) 183 × 110.5 × 25.8 mm
- Video resolution Luminance (brightness): 3 MHz = 240 lines (later, e.g. Philips VR 2840: 3.1 MHz = 250 lines)
- Video resolution chroma (color): approx. 0.5 MHz; degraded color with subcarrier at 625 kHz
- Sound: Long track (stereo) with DNS (Dynamic Noise Suppression)
- Audio track width: mono = 0.6 mm / stereo = 2 × 0.25 mm (track spacing: 0.15 mm)
- Hi-Fi stereo with PCM digital recording over video heads (as with 8mm / Hi8 video) was developed but no longer produced
- Particularities:
- DTF tracking (so-called ATF variant for simpler devices, see below)
- APF scan
- Real-time counter with tape position measurement (from second generation devices at Grundig and Philips)
- Picture search forwards and backwards free of interference zones, both for still images and for time-lapse
- A maximum of 16 hours of playing time per cassette in long-play mode
Video 2000 in the video format war
Due to the relatively late market launch of the system, Video 2000 found it difficult to assert itself against the VHS and Betamax formats . If at all, this was only possible in Western Europe and only for a time. Although the Video 2000 format was technically superior in some areas, it never achieved some key characteristics of VHS and Betamax. Here is a summary:
- Even before Video 2000 was launched, VHS and Betamax were able to gain large market shares. At that time there were also video stores with pre-recorded VHS and Betamax cassettes. The VHS system was so strengthened in terms of market policy through the rental business that the VCR (with its offshoots Longplay and SVR ), Video 2000 and Betamax were pushed out of the market.
- VHS and Betamax recorders were said to be more reliable.
- The first Video 2000 devices had compatibility problems when a Video 2000 cassette was played on a device in which it had not been recorded.
- When programs were exchanged between Grundig and Philips devices, the very first recorders also encountered problems with lip-synchronicity between picture and sound. In addition, the DTF tracking system often failed - a glitch that could not be fully controlled by the end of Video 2000 production. Although the advertising made particular reference to the compatibility with cassettes recorded by others, it could not be fully achieved.
- VHS and Betamax shone with hi-fi stereo sound in the mid-1980s . Despite the Video 2000's DNS noise reduction system, the sound quality was poor due to the lengthways track recording at the very low tape speed. However, in 1985 Philips planned to launch a Video 2000 Hi-Fi recorder with helical recording for the sound. In contrast to VHS or Betamax ( frequency modulation ), the latter should be recorded digitally (PCM) with Video 2000. Optionally, multiple tracks of digital audio should be possible for video recording. A prototype of such a device was presented at the 1984 Hi-Fi and Video Fair in Düsseldorf. This Video 2000 Hi-Fi recorder was no longer produced, however, as the decision was made in Eindhoven and Fürth, the headquarters of Philips and Grundig, to phase out the system.
- Video 2000 never quite achieved the image quality (optimally set devices) of the previous systems VCR, VCR Longplay and Super Longplay SVR due to the design-related lower relative tape-head speed .
- A positive feature of Video 2000 is the patented Autotracking DTF (Dynamic Track Following) by means of actuator-controlled head tracking. With the exception of a simpler Grundig device, which only had automatic tracking similar to the auto-tracking on VHS devices, DTF was a system component of all other Video 2000 devices. This sensitive technology should make the image reproduction for forward, reverse and still image completely free of interference zones.
- The cassettes of the system contain switchable receiving locks in the form of a switchable slide per cassette side.
technology
A difference to all other video formats on the market was that you could record on both sides of the cassette (which is why it was actually a ¼-inch format).
What was really revolutionary about this format, however, was that it managed completely without a synchronous track. This track is used, for example, in VCR or VHS to record sync pulses and thus to control the momentary angle of rotation of the head wheel with respect to the tape feed during playback. However, Video 2000 used special signals to define the video tracks. This technique was also used in Video 8 in 1985, in a simplified form with video heads that were not actuator-controlled but rather rigidly mounted. In Video 2000, it turned out to be complicated and not yet fully developed at the beginning. Even minimally damaged tapes, as can easily occur on frequently used cassettes, led to playback problems. The functional reliability of the DTF system was significantly influenced by the quality of the video tapes. High-quality high-grade tapes with a higher coercive force showed a significantly higher functional reliability with regard to the DTF system.
The Video 2000 standard provides video heads on piezoelectric elements, so-called actuators, so that the heads can precisely follow the video tracks even at tape speeds that deviate from the normal, such as during picture search. This results in an image free of interference stripes. With VHS, such a streak-free picture search was not possible without interference, even with the introduction of several video heads and a technically complex switch matrix for their scanning signals. Only the system developer JVC introduced a so-called "dynamic drum" into a few top devices almost 20 years later. H. a head drum with a motorized adjustable angle of inclination, which can achieve a level of freedom from interference comparable to that of Video 2000 when playing special functions. However, this technology requires a certain amount of time in order to be able to adapt to the inserted tape for the first time at every adjustable speed; only then does the accuracy take place as with Video 2000.
In Video 2000, the head wheel had roughly the diameter of a VHS head wheel (Video 2000: 65 mm, VHS: 62 mm) and was therefore significantly smaller than that of the previous VCR systems , which had a diameter of 105 mm. Video 2000 required a transmission of the piezo control voltage of up to ± 150 volts to the rotating head wheel by means of slip rings. For various reasons, these were also a potential source of errors, but they could be repaired quickly after cleaning the slip rings; with the exception of the first generation of Philips drives, as the head drum had to be removed for cleaning.
The cassettes were coded with three optionally punched holes side by side on each side. These holes were checked by the recorders via contacts, which enabled the recorder to recognize the cassette length (120, 180, 240, 360, 480 or 540 minutes) and the tape material immediately after it was inserted. As a result, from the second generation of devices, it was possible to display a tape counter reading accurate to the minute by evaluating the tachometer impulses of the two tape discs, something that VHS only did years later and never did with Betamax. The end of the tape was switched off on the Video 2000 cassette with the help of vapor-deposited reflective foils on both tape ends.
picture quality
With a video resolution (luminance) of 3 MHz, i.e. H. About 240 lines at 625 lines (576 lines visible) and a color resolution of 500 kHz, Video 2000 is roughly comparable to the first generation of VHS devices, but with reduced color noise, a sharper picture, but slightly higher edge noise.
Through further improvement, especially the quality of the tape material (the later Video 2000 devices could recognize the so-called high-grade cassettes due to the hole coding), the video resolution of the top devices (e.g. Philips VR 2350 , VR 2840, Grundig 2280) increased to 3.1 MHz, which corresponds to about 250 lines.
A further improvement in terms of edge definition and color noise was achieved with the last devices of the XL-Play (only Philips VR 2840) and 2x8 series (Grundig 2280 / 2280a) by reducing the video track width to 16 µm, so that a track image is practically again with the so-called lawn (6.5 µm) between the individual video tracks (with full downward compatibility at the same time) which, in addition to the azimuth angle of the video heads, also reduces crosstalk between the tracks. At the same time, longplay operation could also be covered with the same video heads. The overlap of the 16 µm wide tracks by 2.25 µm resulted in the effective video track of 11.25 µm. VHS uses two separate video heads with correspondingly reduced video tracks for long play and therefore had a better picture quality than Video 2000 in this operating mode; only later in SLP mode (e.g. JVC) was the same technology used with a further reduced belt speed.
Since the format was not further developed from 1985 onwards, the VHS-HQ devices, which were further developed at the same time, were now better in terms of picture quality than Video 2000. Here, the video resolution was also increased to 3.1 MHz (250 lines) and a number of lines further improvements realized through other filters of the HQ circuit. Interestingly enough, this also made it possible to provide copy protection for VHS purchase cassettes, which in turn was ignored by all GRUNDIG VIDEO2000 and VHS devices of the 200, 300 and 400 series.
The image quality of the Betamax system was not quite achieved, however, as this was achieved in particular by the larger video head drum (74.5 mm) and the higher relative speed (5.83 m / s) of the video heads (video resolution 3.2 MHz = 260 lines ). The color resolution and color noise were also slightly better with Betamax compared to Video 2000 and VHS, but the linear sound reproduction was worse due to the low tape speed.
Further improvements to the Video 2000 standard, for example through the already developed hi-fi sound recording via PCM sound via the video heads, were no longer brought onto the market, as was the possibility of a further increase in the video resolution as with the later S-VHS (5 MHz = 400 lines) or ED-Beta (6.25 MHz = 500 lines).
The DTF (Dynamic Track Following) tracking system
The dynamic tracking system enables the video heads to precisely follow the tracks on the tape. This prevents interference zones, such as those that occur in other systems, for example when fast forwarding.
With the dynamic tracking system, the video heads are attached to piezo plates . By applying a voltage of up to ± 150 volts, the platelets are deformed, which shifts the position of the heads.
When recording, the necessary track singing frequencies are recorded on the tape with the FM. A part of this frequency is already read out during the recording - adjacent track - and used for control. The control voltage required for this is usually obtained via a microcontroller by evaluating the "track sensing frequencies" recorded for this purpose. This makes it possible to precisely follow the center of the helical track. The signals obtained in this way are also used for other control systems.
See also
Web links
Individual evidence
- ↑ Service instructions 2x4 super electrical part, page 43