Video tape recorder

"VTR" redirects here. For other uses, see VTR (disambiguation).
1950s AMPEX Quadruplex VR-1000A, the first commercially produced video tape recorder; Quadruplex reel-to-reel tape is 2 inches wide
The first "portable" VTR, the suitcase-sized 1967 AMPEX Quadruplex VR-3000
1976 Hitachi portable VTR, for Sony 1" type C; the source and take-up reels are stacked for compactness. However, only one reel is shown here.

A video tape recorder (VTR) is a tape recorder designed to record video material on magnetic tape. The first practical video tape recorder, using transverse tape head scanning, was developed by Ampex Corporation in 1956. The early VTRs were reel to reel devices which recorded on individual reels of 2 inch (5.08 cm) wide magnetic tape. They were used in television studios, serving as a replacement for motion picture film stock and making recording for television applications cheaper and quicker. Beginning in 1963, videotape machines made instant replay during televised sporting events possible. Improved formats, in which the tape was contained inside a videocassette, were introduced around 1969; the machines which play them are called videocassette recorders. Agreement by Japanese manufacturers on a common standard recording format, so cassettes recorded on one manufacturer's machine would play on another's, made a consumer market possible, and the first consumer videocassette recorder was introduced by Sony in 1971.

History

The first efforts at video recording, using recorders similar to audio recorders with fixed heads, were unsuccessful. The problem was that a video signal has a much wider bandwidth than an audio signal (6 MHz vs 20 kHz), requiring extremely high tape speeds to record it. One of the first efforts was the Vision Electronic Recording Apparatus, a high speed multi-track machine developed by the BBC in 1952.[1] This machine used a thin steel tape on a 21-inch (53.5 cm) reel traveling at over 200 inches (510 cm) per second. Despite 10 years of research and improvements, it was never widely used due to the immense length of tape required for each minute of recorded video. Many other fixed-head recording systems were tried but all required impractically high tape speed.

It became clear a practical video recording technology depended on finding some way of recording the wide-bandwidth video signal without the high tape speed required by linear-scan machines. The solution was the transverse-scan technology invented by Ampex around 1954, in which the recording heads are mounted on a spinning drum and record tracks in the transverse direction, across the tape. This technique recorded a much higher density of data per centimeter of tape, allowing a lower tape speed of 15 inches per sec. to be used. The Ampex VRX-1000 became the world's first commercially successful videotape recorder in 1956. It used the 2" Quadruplex format, using two-inch (5.1 cm) tape.[2] Because of its US$50,000 price, the Ampex VRX-1000 could be afforded only by the television networks and the largest individual stations.[3]

In 1963, Philips introduced its EL3400 1" helical scan recorder (aimed at the business and domestic user) and Sony marketed the 2" PV-100, its first reel-to-reel VTR intended for business, medical, airline and educational use.[4]

The Telcan, produced by the Nottingham Electronic Valve Company and demonstrated on June 24, 1963,[5] was the first home video recorder. It could be bought as a unit or in kit form for £60. However, there were several drawbacks: it was expensive, not easy to put together, and could record only 20 minutes' output at a time in black and white.[6][7][8]

The Sony model CV-2000, first marketed in 1965, was its first VTR intended for home use and was based on half-inch tape.[9] Ampex and RCA followed in 1965 with its own reel-to-reel monochrome VTRs priced under US $1,000 for the home consumer market.

The EIAJ format was a standard half-inch format used by various manufacturers. EIAJ-1 was an open-reel format. EIAJ-2 used a cartridge that contained a supply reel, but not the take-up reel. Since the take-up reel was part of the recorder, the tape had to be fully rewound before removing the cartridge, a slow procedure.

The development of the videocassette followed the replacement by cassette of other open-reel systems in consumer items: the Stereo-Pak 4-track audio cartridge in 1962, the compact audio cassette and Instamatic film cartridge in 1963, the 8-track cartridge in 1965, and the Super 8 home movie cartridge in 1966. Before the invention of the video tape recorder, live video was recorded onto motion picture film stock in a process known as telerecording. Although the first Quadruplex VTRs recorded with good quality, the recordings could not be slowed or freeze framed, so telerecording processes continued to be used for about a decade after the development of the first VTRs.

Technology

Scanning techniques used in video tape recorders. (A) Transverse scanning used in the early Quadriplex system required several vertical tracks to record a video frame. (B) Helical scan, by recording in long diagonal tracks, is able to fit a full video field on each track. The first "full helical" system used one head, requiring tape to wrap fully around drum. (C) "half helical" system with 2 heads only required tape to wrap 180° around drum.

In the transverse-scan technique used in all video tape recorders, the recording heads are mounted in a rapidly-spinning drum which is pressed against the moving tape, so the heads move across the tape in a transverse or diagonal path, recording the video signal in consecutive parallel "tracks" sideways across the tape. This allows use of the entire width of the tape, storing much more data per inch of tape, compared to the fixed head used in audio tape recording, which records a single track down the tape. The heads move across the tape at the high speed necessary to record the high-bandwidth video signal, but the tape moves at a slower speed through the machine. In addition, three ordinary tracks are recorded along the edge of the tape by stationary recording heads. For correct playback, the motion of the heads has to be precisely synchronized with the motion of the tape through the capstan, so a "control track" of synchronizing pulses is recorded. The other two tracks are for the audio channel, and a "cueing" track.

The early machines used the Ampex 2 inch quadruplex system in which the drum had 4 heads and rotated at 14,400 RPM perpendicular to the tape, so the recorded tracks were transverse to the tape axis. With 2 inch tape this required 16 tracks for a single analog NTSC video frame, or 20 for a PAL frame. Since each track was only a fraction of a video frame, quadruplex was not capable of modern editing functions like "freeze frame" or slow motion. (In fact, the quadruplex format could only reproduce recognizable pictures when the tape was playing at normal speed.[10]) But in spite of its drawbacks it remained the broadcasting studio standard until about 1980.

The later helical scan methods used a recording drum with its axis of rotation almost vertical. The tape was wrapped longitudinally around the drum by idler wheels, so the tape heads, instead of moving across the tape at almost 90° to the direction of motion as in the Quadruplex system, moved across the tape at a shallow angle, recording a long diagonal track across the tape. This allowed an entire frame to be recorded per track. This simplified the electronics and timing systems. It also allowed the recorder to be "paused" ("freeze frame") during playback to display a single still frame, by simply stopping the tape transport mechanism, allowing the tape heads to repeatedly pass over the same track.

This recording technique has many potential sources of timing errors. If the mechanism ran at an absolutely constant speed, and never varied from moment to moment, or from the time of recording to the time of playback, then the timing of the playback signal would be exactly the same as the input. However, imperfection being inevitable, the timing of the playback always differs to some extent from the original signal. Longitudinal error (error arising from effects in the long direction of the tape) can be caused by variations in the rotational rate of the capstan drive, stretching of the tape medium, and jamming of tape in the machine. Transverse error (error arising from effects in the cross-tape direction) can be caused by variations in the rotational speed of the scanning drum and differences in the angle between the tape and the scanning heads (usually addressed by video "tracking" controls). Longitudinal errors are similar to the ones that cause wow and flutter in audio recordings. Since these errors are not so subtle and since it is standard video recording practice to record a parallel control track, these errors are detected and servos are adjusted accordingly to dramatically reduce this problem. ↔

VCR

Many of the deficiencies of the reel-to-reel systems were overcome with the invention of the Videocassette recorder (VCR), where the videotape is enclosed in a user-friendly videocassette shell. This subsequently became the most familiar type of VTR known to consumers. In this system, the tape is pre-attached onto two reels enclosed within the cassette, and tape loading and unloading is automated. There is no need for the user to ever touch the tape, and the media can be protected from dust, dirt, and tape misalignments that could foul the recording mechanism. Typically, the only time the user ever touches the tape in a videocassette is when a failure results from a tape getting stuck in the mechanism.

Home VCRs first became available in the early 1970s, with Philips releasing the Model 1500 in England in 1972.[11] It, for the first time, offered users the capability of deciding what they wanted to watch. The first system to be successful with consumers was Sony's Betamax (or Beta) in 1975. It was soon followed by the competing VHS (Video Home System) format from JVC in 1977 [11] and later by other formats such as Video 2000 from Philips, V-Cord from Sanyo, and Great Time Machine from Quasar.

The Beta–VHS format war soon began, while the other competitors quickly disappeared. Betamax sales eventually began to dwindle, and after several years VHS emerged as the winner of the format war. In 1988, Sony began to market its own VHS machines, and despite claims that it was still backing Beta, it was clear that the format was no longer viable in most parts of the world. In parts of South America and in Japan, Betamax continued to be popular and was still in production up to the end of 2002.

Later developments saw magnetic tapes largely replaced by digital video tape formats. Following this, much of the VTR market, in particular videocassettes and VCRs popular at the consumer level, were also replaced by digital media, such as DVD and later Blu-ray optical discs.

Formats and products

Video tape recorder technologies include:

Analog reel-to-reel
Sony Betacam-SP VTP BVW-65 VTR
Professional cassette and cartridge based systems
Standard definition digital videotape formats
1995 Panasonic D5 Digital VTR, model AJ-HD3700H. The front control panel is hinged below the cassette slot, so that it may be tilted outward to a more comfortable viewing angle for the operator.
High definition digital video tape formats
Consumer format

Cultural impact

The Buggles' hit song "Video Killed the Radio Star", the first video ever to air on MTV, contains the lyric "Put the blame on VTR".[13]

See also

References

  1. ↑ "The History of Magnetic Recording". BBC 20 December 2004. Retrieved 15 March 2011.
  2. ↑ "Ampex VRX-1000 - The first commercial videotape recorder in 1956". Cedmagic.com. 1956-04-14. Retrieved 2010-05-31.
  3. ↑ Richard N. Diehl. "Labguy'S World: The Birth Of Video Recording". Labguysworld.com. Retrieved 2010-05-31.
  4. ↑ "Sony Global - Sony History". Sony.net. Archived from the original on September 7, 2009. Retrieved 2010-05-31.
  5. ↑ Albert Abramson, The History of Television, 1942 to 2000 (McFarland, 2003) p99
  6. ↑ "The quest for home video: Telcan home video recorder". Terramedia.co.uk. 2001-10-22. Retrieved 2010-05-31.
  7. ↑ "Total Rewind". Total Rewind. Retrieved 2010-05-31.
  8. ↑ "BBC History". Bbc.co.uk. 1963-06-24. Retrieved 2010-05-31.
  9. ↑ "Sony CV Series Video". Smecc.org. Retrieved 2010-05-31.
  10. ↑ Wink Hackman; Expert training for Sony MVS users worldwide Retrieved December 25, 2015
  11. 1 2 "VCR and Home Video History". Television History - The First 75 Years. TVhistory.TV. Retrieved 24 May 2011.
  12. ↑ 1965 - Sony releases first home video equipment
  13. ↑ Lyrics to "Video Killed the Radio Star"

External links

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