VHS: Difference between revisions
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* Of special note is the format of the VHS logo. In a "true" VHS logo, the horizontal bar of the "H" extends slightly to the left-hand side of the letter. |
* Of special note is the format of the VHS logo. In a "true" VHS logo, the horizontal bar of the "H" extends slightly to the left-hand side of the letter. |
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* In the late 1980s, Tandy [[Radio Shack]] marketed a computer data backup device based on recording to VHS tape. |
* In the late 1980s, Tandy [[Radio Shack]] marketed a computer data backup device based on recording to VHS tape. |
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* Burning eight VHS cassettes releases a similar amount of heat energy as burning a [[couch|sofa]]{{fact}}. |
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== Footnotes == |
== Footnotes == |
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Revision as of 16:14, 25 August 2006
- This article is about the video format. For other uses, see VHS (disambiguation).
The Video Home System, better known by its abbreviation VHS, is a recording and playing standard for video cassette recorders (VCRs), developed by JVC (with some of its critical technology under lucrative licensing agreements with Sony) and launched in September 1976. There is a relatively popular belief that VHS officially stands for Video Home System. In fact it initially stood for Vertical Helical Scan, after the relative head/tape scan technique (making the popular version a backronym), some actually believe that it once stood for Video Head Set, due to the way the cassettes magnetic strip is read with a silver read head.[1]
VHS became a standard format for consumer recording and viewing in the 1980s and 1990s after competing in a fierce format war with Sony's Betamax and, to a lesser extent, Philips' Video 2000. VHS initially offered a longer playing time than the Betamax system, and it also had the advantage of a far less complex tape transport mechanism. Early VHS machines could rewind and fast forward the tape considerably faster than a Betamax VCR since they unthreaded the tape from the playback heads before commencing any high-speed winding. Most newer VHS machines do not perform this unthreading step, as head-tape contact is no longer an impediment to fast winding, due to improved engineering.
The week of 15 June 2003 marked the first time the DVD format (which was launched in the late 1990s) became more popular than VHS in the USA. Although still popular with home recording, the VHS tape has largely been replaced by DVD.
As of July, 2006 most studios have stopped releasing movies in VHS format, opting for DVD-only releases. VHS prerecorded movies, however, are still popular with many collectors.
Technical details
A VHS cassette contains a ½ inch (12.7 mm) wide magnetic tape wound between two spools, allowing it to be slowly passed over the various playback and recording heads of the video cassette recorder. The tape speed is 3.335 cm/s for NTSC, 2.339 cm/s for PAL. A cassette holds a maximum of about 430 m of tape at the lowest acceptable tape thickness, giving a maximum playing time of about 3.5 hours for NTSC and 5 hours for PAL at "standard" (SP) quality. Most cassettes have lower recording times because they use thicker tape, which helps avoid jams; careful users generally avoid the thinnest tapes. More recent machines usually allow the selection of longer recording times by lowering the tape speed: LP mode (for PAL and some NTSC machines) halves the tape speed and doubles the recording time, while EP mode (for NTSC and some newer PAL machines, aka SLP mode) drops the tape speed to one-third, for triple the recording time. Of course, these speed reductions cause corresponding reductions in video quality; also, tapes recorded at the lower speed often exhibit poor playback performance on recorders other than the one they were produced on. Because of this, commercial prerecorded tapes were almost always recorded in SP mode. The only exceptions were "discount" tapes, usually containing children's cartoons or older shows, usually recorded at SLP speed but sometimes including Hi-Fi audio to help enhance sound quality. An unofficial LP mode with half the standard speed exists on some NTSC machines, but is not part of the VHS standard.
As with almost all cassette-based videotape systems, VHS machines pull the tape from the cassette shell and wrap it around the head drum. VHS machines, in contrast to Betamax and Beta's predecessor U-matic, use an M-loading system where the tape is drawn out by two threading posts and wrapped around the head drum (and other tape transport components) in a shape roughly approximating the letter M. (Betamax and U-Matic use a rotating loading disk which more closely approximates the shape of the letter U, hence the name U-Matic.) VHS tapes have approximately 3 MHz of video bandwidth, and a horizontal resolution of about 240 discernible lines per scanline [1]. The frequency modulation of the luminance signal makes higher resolutions impossible within the VHS standard, no matter how advanced the recorder's technology. Signal-to-Noise ratio of the image signal is around 43 dB. The vertical resolution of VHS (and all other analog recording methods) is determined by the TV standard — a maximum of 486 lines are visible in NTSC and a maximum of 576 lines in PAL.
The video bandwidth is achieved with a relatively low tape speed by the use of helical scan recording of a frequency modulated luminance (black and white) signal, to which a frequency-reduced "color under" chroma (hue and saturation) signal is added. In the original VHS format, audio was recorded unmodulated in a single (monaural) linear track at the upper edge of the tape, which was limited in frequency response by the tape speed (about 100Hz-8Khz with 42dB S/N ratio at SP). More recent hi-fi VCRs add higher-quality stereo audio tracks (20Hz-20Khz with more than 70dB S/N ratio at SP) which are read and written by heads located on the same spinning drum that carries the video heads, frequency modulated to the unused frequency range in between the chroma and luma signals. These audio tracks take advantage of depth multiplexing: since they use lower frequencies than the video, their magnetization signals penetrate deeper into the tape. When the video signal is written by the following video head, it erases and overwrites the audio signal at the surface of the tape, but leaves the deeper portion of the signal undisturbed. The excellent sound quality of hi-fi VHS has gained it some popularity as an audio format in certain applications; in particular, ordinary home hi-fi VCRs are sometimes used by home recording enthusiasts as a handy and inexpensive medium for making high-quality stereo mixdowns and master recordings from multitrack audio tape.
Of course, for backward compatibility, hi-fi VCRs still write the linear audio track during recording and can automatically read it during playback if the hi-fi audio is not present.
A peculiarity of VHS machines is a jittering dot at the bottom of the screen, corresponding to the point at which the VCR's electronics switch from one head to the other as the rotating head drum completes reading a stripe of video. The "switching point" used to be obscured in older TV sets which tended to overscan more than newer sets.
Some higher-end VHS and S-VHS VCRs once offered "audio dubbing" and "video dubbing" functions. These would move the tape past the heads and keep the video unchanged while recording new linear audio or keep the linear audio unchanged while recording new video, respectively. This was useful, for example, for laying a song over a previously edited-together montage of short video clips that were the same total duration as that song. Without the dubbing features, this task would have required the tape to be copied to another tape which would cause generational loss. Due to the different ways in which linear and HiFi audio are recorded, these kinds of dubbing were not possible with the HiFi tracks. Another high-end feature was manual audio level control, which made the VHS HiFi format much more useful for high-quality audio-only recording purposes as discussed above. Some higher end machines, particularly S-VHS VCRs made by JVC, still offer audio and video dub features, though most modern VCRs do not.
Another linear control track, at the tape's lower edge, holds pulses that mark the beginning of every frame of video; these are used to fine-tune the tape speed during playback and to get the rotating heads exactly on their helical tracks rather than having them end up somewhere between two adjacent tracks (a feature called tracking). Since good tracking depends on the exact distance between the rotating drum and the fixed control/audio head reading the linear tracks, which usually varies by a couple of micrometers between machines due to manufacturing tolerances, most VCRs offer tracking adjustment, either manual or automatic, to correct such mismatches.
The control can additionally hold index marks. These are normally written at the beginning of each recording session, and can be found using the VCR's index search function: this will fast-wind forward or backward to the nth specified index mark, and resume playback from there. There was a time when higher-end VCRs provided functions for manually removing and adding these index marks — so that, for example, they coincide with the actual start of the program — but this feature has become hard to find in recent models.
Variations
Several improved versions of VHS exist, most notably S-VHS, an improved analogue standard, and D-VHS, which records high definition digital video onto a VHS form factor tape. Devices have also been invented which directly connect a personal computer to VHS tape recorders for use as a data backup device. W-VHS caters for analog high definition video.
Another variant is VHS-C (C for compact), used in some camcorders. Since VHS-C tapes are based on the same magnetic tape as full size tapes, they can be played back in standard VHS players using a mechanical adapter, without the need of any kind of signal conversion. The magnetic tape on VHS-C cassettes is wound on one main spool and uses a gear wheel to advance the tape; the wheel and spool can also be moved by hand. This development hampered the sales of the Betamax system somewhat, because the Betamax cassette geometry prevented a similar development.
There is also a JVC-designed component digital professional production format known as Digital-S or (officially) D9 that uses a VHS form factor tape and essentially the same mechanical tape handling techniques as an S-VHS recorder. This format is the least expensive format to support a pre-read edit. This format is most notably used by Fox for some of its cable networks.
Signal standards
VHS can record and play back all varieties of analogue television signals in existence at the time VHS was devised. However, a machine must be designed to record a given standard. Typically, a VHS machine can only handle signals of the country it was sold in. The following signal varieties exist in conventional VHS:
- PAL/625/25 (most of Western Europe, many parts of Asia (such as China and India) and Africa)
- SECAM/625/25 (SECAM, French variety)
- MESECAM/625/25 (most other SECAM countries, notably the former Soviet Union and Middle East)
- NTSC/525/30 (Most parts of North and South America, Japan, South Korea)
- PAL/525/30 (i.e. PAL-M, Brazil)
Since the 1990s dual- and multistandard VHS machines have become more and more common. These can handle VHS tapes of more than one standard. E.g. regular VHS machines sold in Europe nowadays can typically handle PAL, MESECAM for record and playback, plus NTSC for playback only. Dedicated multistandard machines can usually handle all standards listed, some high end model can even convert a tape from one standard to another by using a built-in standards converter.
S-VHS only exists in PAL/625/25 and NTSC/525/30. S-VHS machines sold in SECAM markets record internally in PAL, and convert to/from SECAM during record/playback, respectively. Likewise, S-VHS machines for the Brazilian market record in NTSC and convert to/from PAL-M.
Tape lengths
Both NTSC and PAL/SECAM VHS cassettes are physically identical (although the signals recorded on the tape are incompatible.) However, as tape speeds differ between NTSC and PAL/SECAM, the playing time for any given cassette will vary accordingly between the systems.
In order to avoid confusion, manufacturers indicate the playing time in minutes that can be expected for the market the tape is sold in:
- T-XXX indicates playing time for NTSC or PAL-M in SP speed.
- E-XXX indicates playing time for PAL or SECAM in SP speed.
It is perfectly possible to record and play back a blank T-XXX tape in a PAL machine or a blank E-XXX tape in an NTSC machine, but the resulting playing time will be different from that indicated. It can easily be derived by multiplying with 3/2 or 2/3, respectively.
For example, a T-120 tape runs for 120 minutes in NTSC-SP, but 180 minutes in PAL-SP. Conversely, an E-300 tape runs for 300 minutes in PAL-SP, but 200 minutes in NTSC-SP.
| Tape Label | Tape Length | Rec. Time (NTSC) | Rec. Time (PAL) | ||
|---|---|---|---|---|---|
| SP | EP/SLP | SP | EP/SLP | ||
| T-120 | 812 ft (247.5 m) | 2hrs | 6hrs | 2hrs 49mins | ?? |
| T-160 | 1075 ft (327.7 m) | 2hrs 40mins | 8hrs | ?? | ?? |
| T-180 | 1210 ft (368.8 m) | 3hrs | 9hrs | ?? | ?? |
| Tape Label | Tape Length | Rec. Time (PAL) | Rec. Time (NTSC) | ||
| E-120 | 173.7 m (570 ft) | 2hrs | ?? | 1hr 26mins | ?? |
| E-180 | 259.4 m (851 ft) | 3hrs | ?? | 2hrs 9mins | ?? |
| E-240 | 348.1 m (1142 ft) | 4hrs | ?? | 2hrs 53mins | ?? |
VHS vs. Betamax
As mentioned, VHS was the winner of a protracted and somewhat bitter format war during the early 1980s against Sony's Betamax format. Since Betamax was widely perceived at the time as the better format, it is often stated that VHS' eventual victory was a victory of marketing over technical excellence. In fact, however, the root causes of VHS' victory are somewhat more complex. Betamax held an early lead in the format war, offering some technical advantages, but by 1980 VHS was gaining due to its longer tape time (3 hours maximum, compared to just 60 minutes for Betamax in USA) and JVC's less strict licensing program. The longer tape time is sometimes cited as the defining factor in the format war, as the longer VHS tapes allowed consumers to record entire programs unattended, but clearly was not relevant in Europe where VHS and Beta running times were similar from the start. Sony ultimately conceded the fight in the late '80s, bringing out a line of VHS VCRs. The format war and the "marketing over technology" claims have taken on a life of their own, and have been used as analogies in the battles of the computer industry, including Apple vs. IBM, Macintosh vs. Windows and Microsoft Internet Explorer vs. Netscape.
Other formats such as 8 mm video cassettes and MiniDV have emerged since, but these formats are by no means in complete competition with VHS. As these cassettes are much more compact in design — which also means the hardware to play and record the tapes has to be more compact than VHS, and therefore more expensive — they are much more suited to portable applications such as camcorders. 8 mm tapes, introduced in the early 1980s, succeeded as a format for camcorders (both in the consumer, and to an extent, professional market), as VHS and Betamax camcorders were unsuitably large and heavy in comparison. MiniDV has largely replaced 8 mm tapes as the de facto camcorder standard in more recent years as it is smaller still (some MiniDV camcorders being no larger than one's hand). In addition, it offers superior audiovisual quality, and the storage of data in digital format on tape makes for improved transfer and editing.
Both VHS and Betamax manufacturers created professional video formats built around the same cassette shells. The professional derivatives of VHS were M and then MII whereas the professional derivative of Betamax was Betacam which has gone on to spawn digital variants. In a complete reversal of the domestic VHS / Betamax battle, in the professional arena the Beta format has been hugely successful, and the VHS derived formats became obsolete. Occasionally this causes some confusion in that people believe that Betamax is a professional studio format, but in fact it is the superficially very similar Betacam format they are thinking of.
DVD and the decline of VHS
Since the release of the DVD format in the United States in 1997, the popularity of VHS in sales and rentals has fallen. Major U.S. retailers Circuit City and Best Buy stopped selling pre-recorded VHS tapes in 2002 and 2003, respectively. This is not to say the format has been completely abandoned: Best Buy, for instance, still sells VCRs and combination DVD/VCRs capable of playing both, as well as blank VHS tapes.
Many films released to theaters from 2004 onwards have later been released only on DVD and not on VHS, and many other new feature films are being released solely on DVD. Moreover, most television programs released as box sets are for sale in DVD format only. Commentators predict that 2006 will be the final year of new releases on VHS, as major studios continue to phase out VHS.
Despite DVD's better quality, VHS is still widely used in home recording of television programs, due to the large installed base and the lower cost of VHS recorders. The commercial success of DVD recording and re-writing has been hindered by a number of factors including:-
- A reputation for being temperamental and occasionally unreliable.
- Shorter recording time: 2 hours on a single-layer disc (up to 4 or 6 hours with higher compression) versus 3 (NTSC) or 5 (PAL/SECAM) hours (up to 15 hours using PAL EP) on a VHS tape. Dual layer recorders and media have not yet become commonplace.
- Buyers are wary of another format war amongst the 2 formats (-R/-RW vs. +R/+RW and Blu-Ray vs. HD DVD).
However, DVRs and TiVos are the main competitors with the VHS in home recording.
List of notable VHS companies
Viacom
- Paramount Home Entertainment (1976-)
- Nickelodeon Video (1993-)
News Corporation
- 20th Century Fox Home Entertainment, currently part of News Corporation (1977-)
- Magnetic Video, the first duplicator/distributor of movies on video cassette for home use (1977-1981)
Lions Gate
- Artisan Entertainment (1984-)
- Vestron Video (1979-)
- Family Home Entertainment (1982-)
- Carolco Home Video (1988-1995)
- Magnum Entertainment (Mid 1980s)
Time Warner
- HBO Video(1978-)
- Warner Home Video (1978-)
- New Line Home Entertainment (1989-)
(Karl)Lorimar Home Video (1984-1992)
The Walt Disney Company
- Buena Vista Home Entertainment (1989-)
- Walt Disney Home Entertainment (1978-)
- Touchstone Home Entertainment (1984-)
- Miramax Home Entertainment (1989-)
Sony
- Sony Pictures Home Entertainment (1978-)
- MGM Home Entertainment (1979-)
- Orion Home Video (1988-1997)
NBC Universal
- Universal Home Entertainment (1980-)
- NBC Home Video (1981-)
- Goodtimes Home Video (1980-)
Heron Communications
- Media Home Entertainment (1978-1992)
- Hi-Tops Video (1985-1992)
Others
- Simitar Entertainment (1980s-1990s)
- Anchor Bay Entertainment (1980s-)
- Viz Video (1993-)
Outside of the United States
Australia: Communications and Entertainment Limited (Early 1980s-Mid 1990s)
Canada: HGV Video Productions (1980-Present, Canadian counterpart of Goodtimes Home Video) Astral Video (Mid 1980s-1996)
France: StudioCanal Video
Japan: Bandai Visual - Emotion (1983-) Toei Home Video (?-Present)
Mexico: Televisa Home Entertainment (dates unknown)
South Africa: Nu Metro Home Entertainment (1987-) Ster-Kinekor Home Video (1993-)
Spain: Filmax Home Video (1988-Present) Video Diversion (Mid-1980s) Lauren Films Video (1980s-Present)
United Kingdom: Video Gems (Mid 1980s-1996) Guild Home Video (1984-?) Telstar Home Entertainment (2000s) BBC Video (1980-)
Trivia
- The distinctive font used in the VHS logo is called "Lee". It was created in 1972 by Leo Weisz for Visual Graphics Corporation (VGC).
- Of special note is the format of the VHS logo. In a "true" VHS logo, the horizontal bar of the "H" extends slightly to the left-hand side of the letter.
- In the late 1980s, Tandy Radio Shack marketed a computer data backup device based on recording to VHS tape.
Footnotes
- ^ Some early reports claim the name originally stood for Victor Helical Scan System. In the absence of an authoritative source for the claim that Video Home System is the official meaning, such claims for about this new meaning should be viewed skeptically. The JVC VHS trademark Web site makes no such claim.
External links
- The 'Total Rewind' VCR museum, covering the history of VHS and other vintage formats
- BBC News article: Death of video recorder in sight
- Video tape time comparisons for NTSC vs. PAL
VHS is also a small partnership operating in west lothian, they have recetnly upgraded from the classic VHS mobile to the new BMW mobile. This is approved by many of the customers and has sent profits soaring.