The 1970s was a period when video recording became a major contributor to the television industry. Like many other technological innovations, each of several companies made an attempt to produce a television recording standard that the majority of the world would embrace. At the peak of it all, the home video industry was caught up in a series ofvideotape format wars. Two of the formats, VHS and Betamax, received the most media exposure. VHS would eventually win the war, and therefore succeed as the dominant home video format, lasting throughout the tape format period.[3]

In later years, optical discformats began to offer better quality than video tape. The earliest of these formats, Laserdisc, was not widely adopted, but the subsequent DVD format eventually did achieve mass acceptance and replaced VHS as the preferred method of distribution after 2000.[4]By 2006, film studios in the United States had stopped releasing new movie titles in VHS format. On December 31, 2008, the last major United States supplier of pre-recorded VHS tapes, Distribution Video Audio Inc. of Palm Harbor, Florida, shipped its final truckload.[2]As of 2010, most of the VHS tapes being produced are 6 and 8 hour blank tapes.In 1971, JVC engineers Yuma Shiraishi and Shizuo Takano led the effort in developing the VHS tape format.[5]JVC originally collaborated with Sony Corporation and Matsushita Electric (aka Panasonic, National in Japan) in building a home video standard for the Japanese consumer.[6]Soon after, Sony and Matsushita broke away from the collaboration effort, in order to work on video recording formats of their own. Sony started working on Betamax, while Matsushita started working on VX.

By the end of 1971, JVC produced an internal document titled VHS Development Matrix. In the document, it listed twelve objectives in building a home video recording unit.[7]Suddenly, the commercial video recording industry in Japan took a financial hit. As a result, JVC cut its budgets and restructured its video division - even going as far as shelving the VHS project. However, despite the lack of funding for the VHS project, Takano and Shiraishi continued to work on the project in secrecy. By 1973, the two engineers successfully produced a functional prototype.[7]

In 1974, the Japanese government started a standards war of its own. The Ministry of International Trade and Industry (MITI) attempted to force the Japanese video industry to standardize on just one recording format, for the sake of saving the country from consumer confusion of having too many video formats on the market to choose from.[8]Later, Sony had a functional prototype of the Betamax format, and was very close to releasing a finished product. With this prototype, Sony persuaded the MITI to adopt Betamax as the standard, and allow it to license the technology to other companies.[7]

JVC believed that an open standard worked in the best interest of the consumer, as sharing the format among competitors without licensing the technology was better for the consumer. To prevent the MITI from adopting Betamax, JVC made an attempt to have other companies accept VHS, and thereby work against Sony and the MITI.[9]It was a major key to have Matsushita on-board because Matsushita was Japan's largest electronics manufacturer at the time.[9]JVC succeeded in persuading Matsushita to back the VHS format because Matsushita was afraid to allow Sony to become a leader, and Betamax could only record one hour of video.[9]Matsushita's backing of JVC persuaded Mitsubishiand Sharp to back the VHS standard as well.[7]Sony's release of its Betamax unit to the Japanese market in 1975 placed further pressure on the MITI to side with the company. However, the collaboration of JVC, Matsushita, Mitsubishi and Sharp was much stronger, and eventually lead the MITI to drop its push for an industry standard.

[edit]Initial releases of VHS-based devices

The first VCR to use VHS was the Victor HR-3300, and was introduced by the president of JVC at the Okura Hotel on September 9, 1976.[10][11]JVC started selling the HR-3300 in Akihabara, Tokyo, Japan on October 31, 1976.[10]The United States received its first VHS-based VCR - the RCA VBT200 on August 23, 1977.[12]The RCA unit was designed by Matsushita, and was the first VHS-based VCR manufactured by a company other than JVC. The United Kingdom later received its first VHS-based VCR - the Victor HR-3300EK in 1978.[13]

Quasar and General Electric would follow-up with VHS-based VCRs - all designed by Matsushita.[14]By 1978, Matsushita alone produced just over half of all Japanese VCRs.[15]

[edit]Technical details[edit]Cassette and tape design

Bottom view of VHS with magnetic tape exposed

Top view of VHS with front casing removed

The VHS cassette is a 187 mm wide, 103 mm deep, 25 mm thick plastic shell held together with five Phillips headscrews. The flip-up cover that protects the tape has a built-in latch with a push-in toggle on the right side (see bottom view image). The VHS cassette also includes an anti-despooling mechanism (see the top view): several plastic parts near the front label end of the cassette between the two spools. The spool brakes are released by a push-in lever within a 6.35 mm hole accessed from the bottom of the cassette, about 19.05 mm in from the edge label.

There is a clear tape leader at both ends of the tape to provide an optical auto-stop for the VCR transport mechanism. A light source is inserted into the cassette through the circular hole in the center of the underside when loaded in the VCR, and two photodiodesare located to the left and right sides of where the tape exits the cassette. When the clear tape reaches one of these, enough light will pass through the tape to the photodiode to trigger the stop function; in more sophisticated machines it will start rewinding the cassette when the trailing end is detected. Early VCRs used an incandescent bulb as the light source, which regularly failed and caused the VCR to erroneously think that a cassette is loaded when empty, or would detect the blown bulb and stop functioning completely. Later designs use an infraredLED which had a much longer lifetime.

The recording media is a 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.

VHS M-loading system.

As with almost all cassette-based videotape systems, VHS machines pull the tape from the cassette shell and wrap it around the head drum which rotates at 1800 rpm in NTSC machines[16]and at 1500 rpm for PAL. VHS machines, in contrast to Betamax and Beta's predecessor U-matic, use an "M-loading" system, also known as M-lacing, where the tape is drawn out by two threading posts and wrapped around more than 180 degrees of the head drum (and also othertape transport components) in a shape roughly approximating the letter M.

[edit]Tracking adjustment and index marking

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 television program - but this feature has become hard to find in recent models.

By the late 1990s, some high-end VCRs offered more sophisticated indexing. For example, Panasonic's Tape Library system assigned an ID number to each cassette, and logged recording information (channel, date, time and optional program title entered by the user) both on the cassette and in the VCR's memory for up to 900 recordings (600 with titles).[17]

[edit]Recording capacity

The interior of a modern VHS VCRshowing the drum and tape.

A VHS cassette holds a maximum of about 430 m (1,410 ft.) of tape at the lowest acceptable tape thickness, giving a maximum playing time of about 4 hours in an DF480 forNTSC and five hours in an E-300 for PAL at "standard play" (SP) quality. Other speeds include "long play" (LP) (Not all VCRs include this record mode), and "extended play" (EP) or "super long play" (SLP); For NTSC, LP and EP/SLP doubles and triples the recording time accordingly, but these speed reductions cause a slight reduction in video quality - from the normal 250 lines in SP, to 230 analog lines horizontal. Also, video recorded onto tapes at the lower speed often exhibit poor playback performance on recorders other than the one they were produced on. As a result, commercial pre-recorded tapes were almost always recorded in SP mode. In some cases, budget labels such as Video Treasures (both LP and EP),Starmaker(EP), Burbank Video (LP), Avid Home Entertainment (EP), GoodTimes Entertainment (LP), and even Disney (LP) and Paramount(EP) commonly used a slower speed to reduce the amount of tape required as a cost-saving method.

[edit]Video recording

VHS tapes have approximately 3 MHz of video bandwidth and 400 kHz of chroma bandwidth, which is achieved at a relatively low tape speed by the use of helical scan recording of a frequency modulated luminance(black and white) signal, with a down-converted "color under" chroma(color) signal recorded directly at the baseband. Each helical track contains a single field ('even' or 'odd' field, equivalent to half a frame) encoded as an analog raster scan, similar to analog TV broadcasts. The horizontal resolution is 170 lines per scanline, and the vertical resolution (the number of scanlines) is the same as the respective analog TV standard (576 for PAL or 486 for NTSC). In modern-day digital terminology, VHS is roughly equivalent to 333x480 pixels luma and 40x480 chroma resolutions (333x480 pixels=159,840 pixels or 0.16MP (1/6 of a MegaPixel)).[18]

JVC would counter 1985's SuperBeta with VHS HQ, or High Quality. The frequency modulation of the VHS luminance signal is limited to 3 megahertz which makes higher resolutions impossible, but an HQ branded deck includes luminance noise reduction, chroma noise reduction, white clip extension, and improved sharpness circuitry. The effect was to increase the apparent horizontal resolution of a VHS recording from 240 to 250 analog (equivalent to 333 pixels from left-to-right, in digital terminology). The major VHS OEMs resisted HQ due to cost concerns, eventually resulting in JVC reducing the requirements for the HQ brand to white clip extension plus one other improvement.

In 1987 JVC introduced a new format called Super VHS which extended the bandwidth to over 5 megahertz, yielding 420 analog horizontal (560 pixels left-to-right).

[edit]Audio recording[edit]Original linear system

In the original VHS format, audio was recorded as baseband in a single linear track, at the upper edge of the tape, similar to how an audio compact cassette operates. The recorded frequency range was dependent on the linear tape speed. For the VHS SP mode, this resulted in a mediocre frequency response of roughly 100 Hz to 10 kHz. The signal-to-noise ratio (SNR) was an acceptable 42 dB. Both parameters degraded significantly with VHS's longer play modes, with EP frequency response peaking at 4 kHz.

Audio cannot be recorded on a VHS tape without recording a video signal, even in the audio dubbing mode. If there is no video signal to the VCR input, the VCR will record black as well as generate a control track while the audio is being recorded.

More expensive decks offered stereo audio recording and playback. Linear stereo, as it was called, fit two independent channels in the same space as the original mono audiotrack. While this approach preserved acceptable backward compatibility with monoaural audio heads, the splitting of the audio track degraded the signal's SNR to the point that audible tape hiss was objectionable at normal listening volume. To counteract tape hiss, decks applied Dolby B noise reduction for recording and playback. Dolby B dynamically boosts the mid-frequency band of the audio program on the recorded medium, improving its signal strength relative to the tape's background noise floor, then attenuates the mid-band during playback. Dolby B is not a transparent process, and Dolby-encoded program material will exhibit an unnatural mid-range emphasis when played on non-Dolby capable VCRs.

High-end consumer recorders took advantage of the linear nature of the audio track, as the audio track could be erased and recorded without disturbing the video portion of the recorded signal. Hence, "audio dubbing" and "video dubbing", where either the audio or video are re-recorded on tape (without disturbing the other), were supported features on prosumer linear video editing-decks. Without dubbing capability, an audio or video edit could not be done in-place on master cassette, and requires the editing output be captured to another tape, incurring generational loss.

Studio film releases began to emerge with linear stereo audiotracks in 1982. From that point onward nearly every home video releases by Hollywood featured a Dolby-encoded linear stereo audiotrack. However, linear stereo was never popular with equipment makers or consumers.

[edit]Hi-Fi audio system

Around 1984, JVC added Hi-Fi audio to VHS (in response to Betamax's introduction of Beta Hi-Fi.) Both VHS Hi-Fi and Betamax Hi-Fi delivered flat full-range frequency response (20 Hz to 20 kHz), excellent 70 dB signal-to-noise ratio (in consumer space, second only to the compact disc), dynamic rangeof 90 dB, and professional audio-grade channel separation (more than 70dB). VHS Hi-Fi audio is achieved by using audio frequency modulation (AFM), recording each of the 2 stereo channels (L, R) on a frequency-modulated carrier and embedding the modulated audio signal pair into the video signal. To avoid crosstalk and interference from the primary video carrier, VHS's implementation of AFM relied on a form of magnetic recording called depth multiplexing. The modulated audio carrier pair was placed under the luminance carrier (below 1.6 MHz), and recorded first. Subsequently, the video head erases and re-records the video signal over the same tape surface, but video signal's higher center frequency results in a shallower magnetization of the tape, allowing both the video and residual AFM audio signal to coexist on tape. (PAL versions of Beta Hi-Fi use this same technique). During playback, VHS Hi-Fi recovers the depth-recorded AFM signal by subtracting the audio head's signal (which contains the AFM signal contaminated by a weak image of the video signal) from the video head's signal (which contains only the video signal), then demodulates the left and right audio channels from their respective frequency carriers. The end result of the complex process was audio of outstanding fidelity, which was uniformly solid across all tape-speeds (EP or SP.) Since JVC had gone through the complexity of ensuring Hi-Fi's backward compatibility with non-Hi-Fi VCRs, virtually all studio home video releases contained Hi-Fi audio tracks, in addition to the linear audio track. Under normal circumstances, all Hi-Fi VHS VCRs will record Hi-Fi and linear audio simultaneously to ensure compatibility with VCRs without Hi-Fi playback, though only early high-end Hi-Fi machines provided linear stereo compatibility.

Due to the path followed by the video and Hi-Fi audio heads being striped and discontinuous-unlike that of the linear audio track-head-switching is required to provide a continuous audio signal. Misalignments may lead to imperfect joining of the signal, resulting in low-pitched buzzing.[19]The problem is known as "head chatter," and tends to increase as the audio heads wear down.

The sound quality of Hi-Fi VHS stereo is comparable to the quality of CD audio, particularly when recordings were made on high-end or professional VHS machines that have a manual audio recording level control. This high quality compared to other consumer audio recording formats such as compact cassette attracted the attention of amateur and hobbyist recording artists. Home recordingenthusiasts occasionally recorded high quality stereo mixdowns and master recordings from multitrackaudio tape onto consumer-level Hi-Fi VCRs. However, because the VHS Hi-Fi recording process is intertwined with the VCR's video-recording function, advanced editing functions such as audio-only or video-only dubbing are impossible. Some VHS decks also had a "simulcast" switch, allowing users to record an external audio input along with off-air pictures. Some televised concerts offered a stereo simulcast soundtrack on FM radio and as such, events like Live Aidwere recorded by thousands of people with a full stereo soundtrack despite the fact that stereo TV broadcasts were some years off (especially in regions that adopted NICAM). Other examples of this included network television shows such as Friday Night Videos and MTV for its first few years in existence.

The considerable complexity and additional hardware limited VHS Hi-Fi to high-end decks for many years. While linear stereo all but disappeared from home VHS decks, it was not until the 1990s that Hi-Fi became a more common feature on VHS decks. Even then, most customers were unaware of its significance and merely enjoyed the better audio performance of the newer decks.

[edit]Variations

Victor S-VHS (left) and S-VHS-C (right).

VHS-C adapter

[edit]Super-VHS / ADAT / SVHS-ETMain articles: S-VHS and D-VHS

Several improved versions of VHS exist, most notably Super-VHS (S-VHS), an analog video standard with improved video bandwidth. S-VHS improved the luminance resolution to 400 horizontal lines (versus 250 for VHS/Beta and 500 for DVD). The audio-system (both linear and AFM) is the same. S-VHS made little impact on the home market, but gained dominance in the camcorder market due to its superior picture quality.

The ADAT format provides the ability to record multitrack digital audio using S-VHS media. JVC also developed SVHS-ET technology for its Super-VHS camcorders and VCRs, which simply allows them to record Super VHS signals onto lower-priced VHS tapes, albeit with a slight blurring of the image. Nearly all Super-VHS camcorders and VCRs made today have SVHS-ET ability.

[edit]VHS-C / Super VHS-CMain article: VHS-C

Another variant is VHS-Compact (VHS-C), originally developed for portable VCRs in 1982, but ultimately finding success in palm-sized camcorders. The longest tape available holds 60 minutes in SP mode and 180 minutes in EP mode. 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 adapter does not require a battery to function and is solely a mechanical adapter. It has an internal hub to engage with the VCR mechanism in the location of a normal full-size tape hub, driving the gearing on VHS-C cassette. Also when a VHS-C cassette is inserted into the adapter, a small swing-arm pulls the tape out of the miniature cassette to span the standard tape path distance between the guide rollers of a full-size tape. This allows the miniature cassette to use the same tape loading mechanism of the full-size tape.

Super VHS-C or S-VHS Compact was developed by JVC in 1987. S-VHS provided an improved luminance and chrominance quality, yet S-VHS recorders were compatible with VHS tapes.[20]

Sony Betamax was unable to shrink that form any further, so instead they developed Video8/Hi8 which was in direct competition with the VHS-C/S-VHS-C format throughout the 80s, 90s, and 2000s. Ultimately neither format "won" and both continue to be sold in the low-end market (examples: JVC SXM38 and Sony TRV138).

[edit]W-VHS / Digital-VHS (high-definition)Main articles: W-VHS and D-VHS

W-VHS allowed recording of MUSEHi-Vision analog high definition television, which was broadcast in Japan from 1989 until 2007. The other improved standard, called Digital-VHS (D-VHS), records digital high definition video onto a VHS form factor tape. D-VHS can record up to 4 hours of ATSC digital television in 720p or 1080i formats using the fastest record mode (equivalent to VHS-SP), and up to 40 hours of standard definition video at slower speeds.

[edit]D9Main article: Digital-S

There is also a JVC-designed component digital professional production format known as Digital-S, or officially under the name 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 Sel-Syncpre-read for video editing. This format is most notably used by Fox for some of its cable networks.

[edit]Accessories

Shortly after the introduction of the VHS format, VHS tape rewinders were developed. These devices served the sole purpose of rewinding VHS tapes. Proponents of the rewinders argued that the use of the rewind function on the standard VHS player would lead to kinks in the tape that would affect playback quality. Many lower end VCR's would leave the tape wound around the video head whilst rewinding or fast forwarding, so the rewinders were of some benefit on these machines, to save additional tape and head wear. The rewinder would rewind the tapes smoothly and also normally do so at a faster rate than the standard rewind function on VHS players. However some rewinder brands did have some frequent abrupt stops, which occasionally led to tape damage.

Some devices were marketed which allowed a personal computer to use a VHS recorder as a data backupdevice. The most notable of these was ArVid, widely used in Russia and CIS states. In the United States similar systems were manufactured by Corvus and Alpha Microsystems.[21]Also available was Backer from Danmere Ltd.of England.

[edit]Signal standards

VHS can record and play back all varieties of analog 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:

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 Americas, Japan, South Korea)
PAL/525/30 (i.e., PAL-M, Brazil)
PAL/625/25 (most of Western Europe, Australia, New Zealand, many parts of Asia such as China and India, some parts of South America such as Argentina, Uruguay and the Falklands, and Africa)

Note that PAL/625/25 VCRs allow playback of SECAM (and MESECAM) tapes with a monochrome (black and white) picture (and vice-versa) as the line standard is the same. Since the 1990s, dual- and multi-standard VHS machines have become more and more common. These can handle VHS tapes of more than one standard. For example, regular VHS machines sold in Australia and Europe nowadays can typically handle PAL, MESECAM for record and playback, plus NTSC for playback only (provided the TV is able to display NTSC's 525/30 line standard - most[citation needed] can). Dedicated multistandard machines can usually handle all standards listed, some high end models can even convert the content of a tape from one standard to another on-the-fly during playback 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.

A small number of VHS decks are able to decode closed captions on prerecorded video cassettes. A smaller number still are able, additionally, to record subtitlestransmitted with world standard teletextsignals (on pre-digital services), simultaneously with the associated program.

[edit]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. 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.

To calculate the playing time for a T-XXX tape in a PAL machine, use this formula: PAL/SECAM Recording Time = T-XXX in minutes * (6.6/4.69)

And to calculate the playing time for an E-XXX tape in an NTSC machine, use this formula: NTSC Recording Time = E-XXX in minutes * (4.69/6.6)

Some new Panasonic NTSC/ATSC recorders also include a Very long Play (VP) mode which is not part of the official specification. It enables recordings at 1/5 the SP speed, such that a T-180 holds 3*5 == 15 hours. [22]

E-XXX indicates playing time in minutes for PAL or SECAM in SP and LP speeds.
T-XXX indicates playing time in minutes for NTSC or PAL-M in SP, LP, and EP/SLP speeds.
SP is Standard Play, LP is Long Play (1/2 speed), EP/SLP is extended/super long play (1/3 speed) VHS single
VHS single, also known as videotape single or Video 45s (a play on the term "45" when used to describe vinyl records) is a music single, using a standard-sized VHS cartridge. The format has existed since the early 1980s. In 1983, British synthpop band The Human League released the UK's first commercial video single on both VHS and Betamax as "The Human League Video Single".[23]It was not a huge commercial success due to the high retail price of £10.99, compared to £1.99 for a vinyl single.
The VHS single format gained higher levels of mainstream popularity when Madonnareleased "Justify My Love" as a video single in 1990 following the blacklisting of the video by MTV.[citation needed] U2also released "Numb", the lead singlefrom their 1993 albumZooropaas a video single.[clarification needed]
Despite the success of these releases, the video single struggled as its releases were relatively periodical, the technology slowly being superseded first by CD Video(which proved unsuccessful due to the cost of capable LaserDiscplayers to play the video portion), music CDs with computer-accessible video files, then, by the early 2000s, by both DVD singlesand CD+DVD releases.
[edit]Other uses
VHS was also commonly included in various products and services - including exercise equipment, kitchen appliances, and even computer software. Corporations used the VHS format to deliver addresses made by company executives to regional offices. Manufacturers would send out VHS tapes to their service centers, to demonstrate how to repair a new product. And retail stores would play VHS tapes demonstrating a product on a television set, requiring a VCR that supported encore function replay or auto rewind play.

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