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2-inch quadruplex videotape (also called 2″ quad, or just quad, for short) was the first practical and commercially successful analog recording videotape format.〔(videopreservation.conservation-us.org, Chapter 6 All About Videotape )〕 It was developed and released for the broadcast television industry in 1956 by Ampex, an American company based in Redwood City, California.〔(quadvideotapegroup.com History )〕 This format revolutionized broadcast television operations and television production, since the only recording medium available to the TV industry before then was film used for kinescopes, which was much more costly to utilize and took time to develop at a film laboratory. In addition, kinescope images were usually of obviously inferior quality to the live television broadcast images they recorded, whereas quadruplex videotape preserved almost all the image detail of a live broadcast. Since most United States West Coast network broadcast delays done by the television networks at the time were done with film kinescopes that needed time for developing, the networks wanted a more practical, cost-effective, and quicker way to time-shift television programming for later airing on the West Coast. Broadcasters also sought a recording medium that was not as costly or time-consuming to edit and develop as film. Faced with these challenges, broadcasters sought to adapt magnetic tape recording technology (already in use for recording audio) for use with television as well. The name "quadruplex" refers to the use of four magnetic record/reproduce heads mounted on a headwheel spinning transversely (width-wise) across the tape at a rate of 14,400 rpm for NTSC 525 lines/30fps-standard quad decks, and at 15,000 rpm for those using the PAL 625 lines/25fps video standard. This method was called quadrature scanning, as opposed to the helical scan transport used by later videotape formats. The tape ran at a speed of either per second for NTSC 525/30 video recording, or per second for PAL 625/25 video, and the audio, control, and cue tracks were recorded in a standard linear fashion near the edges of the tape. The cue track was used either as a second audio track, or for recording cue tones or time code for linear video editing.〔(Videopreservation.conservation-us.org Chapter 5 The VTR )〕 A typical reel of quad tape holds approximately one hour of recorded material at 15 inches per second. The quadruplex format employs segmented recording; each transversely recorded video track on a 2-inch quad videotape holds one-sixteenth (NTSC) or one-twentieth (PAL)〔(Videotape formats )〕 of a field of video. This meant that 2-inch quad did not support "trick-play" functions, such as still, shuttle, and reverse or variable-speed playback. (In fact, the quadruplex format could only reproduce recognizable pictures when the tape was playing at normal speed.〔http://www.liquisearch.com/helical_scan/contrast_with_quadruplex_recording second paragraph, last sentence; Retrieved September 17, 2015〕〔(Wink Hackman; Expert training for Sony MVS users worldwide ) Retrieved September 17, 2015〕) However, it was capable of producing extremely high-quality images containing about 400 horizontal lines of video resolution, and remained the ''de facto'' industry standard for television broadcasting from its inception in 1956 to the mid-1980s, when newer, smaller, and lower-maintenance videotape formats superseded it.〔(videopreservation.conservation-us.org Home page )〕 There were three different variations of 2-inch quad: *Low-band, which was the first variety of quad introduced by Ampex in 1956, *High-band, which used a wider bandwidth for recording video to the tape, resulting in higher-resolution video from the VTR, and *Super High-band, which used a pilot tone for better timebase stability, and higher coercivity tape. Most quad machines made later in the 1960s and 1970s by Ampex could play back both low and high-band 2-inch quad tape.〔(Videopreservation.conservation-us.org Chapter 9, VTR Interchangeability )〕 ==History== Time-shifting of television programming for the West Coast of the United States by the networks in the 1950s (in order to broadcast their programming at the same local time on the East and West Coasts) using kinescope films was quite a rushed and perilous ordeal. This was due to there being only three hours for the West Coast branches of the TV networks to receive video for the programming from the East Coast (live via leased microwave relay or coaxial cable circuits provided by the phone company (AT&T) at the time), and then to record such to kinescope films, and finally to develop the film to be aired three hours later on the West Coast. This usually meant the kinescope was aired almost immediately after it came straight out of the developing equipment, still warm from the film dryer. These were referred to by the networks as "hot kines". By 1954, the networks used more raw film stock for kinescopes than all of the Hollywood film studios combined, spending up to $4,000 per half hour.〔〔(History of Tape Recording )〕 They were desperate to obtain a quicker, less expensive, and more practical solution. In the early 1950s, Ampex and several other companies such as Bing Crosby Enterprises (BCE) and RCA were competing to release a videotape format. RCA and BCE did release working prototypes of their recorders, but their downfall was that they all used a longitudinal (stationary-head) method of recording, much like audio tape recorders. This meant that the tape had to be recorded at an extremely high speed (around /s) in order to accommodate sufficient bandwidth to reproduce an adequate video image (at least 2–3 MHz for a watchable image), in turn requiring large amounts of tape on large reels. At the same time, the BBC developed a similar stationary-head video tape recorder (VTR) system that saw some on-air use, called VERA (Vision Electronic Recording Apparatus). Ampex, seeing the impracticality of the prototype BCE and RCA VTRs, started to develop a more practical videotape format with tape economy in mind, as well as providing a solution to the networks' West Coast delay woes. Starting in 1952, Ampex built the Mark I prototype VTR,〔(Mark I head from lionlamb.us )〕〔(Mark I head and chart )〕 using -wide tape. Ampex decided that instead of having the tape move fast across the head to record enough bandwidth for video, that the head would move fast across the tape instead. This resulted in the Mark I using arcuate scanning, which consisted of a spinning disk with a face (where the heads were mounted) which contacted the tape (as opposed to the edge of the headwheel with transverse quadrature scanning). This resulted in an arc-shaped track being recorded across the width of the tape.〔(danalee.ca Transverse Quad chart )〕 Arcuate scanning resulted in a head-to-tape speed of about /s, but problems with timebase stability of the reproduced video signal from the tape led Ampex to abandon arcuate scanning in favor of the more reliable transverse scanning system.〔(terramedia.co.uk 1956 March 14, Ampex VTR demonstration )〕〔(videopreservation.conservation-us.org Chapter 14, Maintenance, Troubleshooting, And Minor Repairs )〕 Ampex continued through the mid-1950s with the Mark II〔(Mark II from lionlamb.us )〕 and Mark III〔(Mark III )〕 prototype recorders, which now used transverse scanning. The Mark II used frequency modulation for recording video to tape, resulting in a much-improved, but still noisy, video image (the Mark I had used amplitude modulation, which resulted in a very poor-quality video signal reproduced from the tape, compounded as well by the shortcomings of the machine's arcuate scanning). The Mark III had improved signal-processing and servo electronics, resulting in much better video reproduction. The Mark III worked well, but its appearance was quite that of a prototype, and not a finished, saleable product. It was in a makeshift wooden case, with several parts of its chassis externally mounted in partially filled racks. Ampex then built the Mark IV by putting Mark III components into a sleek metal console and fully populated rack-mount cases. The Mark IV〔(Mark 4 )〕 was the machine first publicly demonstrated at the National Association of Radio and Television Broadcasters (now the NAB) convention (the NAB Show) in Chicago on April 14, 1956. After William Lodge of CBS finished his speech, the Mark IV replayed his image and words almost immediately, causing "pandemonium" among the astonished attendees.〔Wolpin, Stewart. "(The Race to Video )". ''Invention & Technology'', Fall 1994.〕 The earlier Mark III was given some cosmetic improvements, and was also demonstrated at Ampex headquarters in Redwood City the same day. Both demonstrations were a success, and Ampex took $2 million in orders for the machine in four days.〔 Ampex later released the first manufactured models of Quad VTR based on the Mark IV which were also prototypes, the VRX-1000,〔(VRX-1000 being made at Ampex )〕 of which 16 were made. Machines made afterward were the final production models, and were designated as the VR-1000.〔(The First Videotape Machines at KRLD-TV, a VR-1000 )〕 The advertised price for the Ampex Videotape Recorder in late 1956 was $45,000.〔"How Much Should a Tape Recorder Cost? (ad )" Broadcasting-Telecasting, 15 October 1956, 220. http://americanradiohistory.com/Archive-BC/BC-1956/1956-10-15-Quarter-Century-BC.pdf〕 In 1957, shortly after Ampex's introduction of the 2-inch quad format, RCA introduced a quad-compatible VTR, the TRT-1A. RCA referred to it as a "Television Tape Recorder", since the word "videotape" was a trademark of Ampex at the time.〔(The museum for retired broadcasting equipment in the UK )〕 RCA was able to make the TRT-1A and its later machines compatible with 2-inch quad because Ampex assisted RCA in doing so, as an expression of gratitude for RCA assisting Ampex with making their later quad machines after the VR-1000 color-capable. Initially, the VR-1000 was only natively capable of recording and playing back black and white video, but RCA had modified several VR-1000s to record color video for the NBC TV network (which RCA owned at the time) in the late 1950s, since NTSC color video programming was already underway at NBC. Ampex developed and released updated and improved models of their quad decks, beginning with the VR-1000B in mid-1959. At that time, Ampex advertised that some 360-plus VR-1000s had been sold worldwide, more than 250 in the U.S.—roughly 30 at each network, 100 by independent stations, and 20 by production companies.〔"Announcing the New Ampex VR-1000B," Broadcasting-Telecasting, 22 June 1959, 58-59. http://americanradiohistory.com/Archive-BC/BC-1959/1959-06-22-BC.pdf〕 The second-generation VR-2000〔(VR-2000 )〕 appeared in 1964. followed by a scaled-down economy version, the VR-1200, in 1966 and the AVR series of VTRs, AVR-1, AVR-2, and AVR-3 in the 1970s. The AVR-2 was the most compact of quad VTRs, using conventional 120 volt (V) single-phase household-type AC power to operate, rather than the 208 or 220 V three-phase AC power required by larger quad machines. RCA released later models of quad VTRs as well, such as the TR-22, TR-70, and TR-600. The Fernseh Div. of Bosch in Germany released the BCM-40 quadruplex VTR in the 1970s. It was only marketed in Europe, and was not sold in the U.S. CBS was the first television network to use 2-inch quad videotape, using it for a West Coast delay of ''Douglas Edwards and the News'' on November 30, 1956.〔"(Charles P. Ginsburg )". ''Memorial Tributes: National Academy of Engineering'', Vol. 7. 1994: The National Academies Press, Washington DC.〕 The CBS show ''Arthur Godfrey's Talent Scouts'' on December 24, 1956 became the first entertainment program to be broadcast live to the nation from New York and taped for a time-delayed rebroadcast in the Pacific Time Zone.〔Val Adams, "C.B.S. Shows Off Tape-Recorded TV", ''New York Times'', Dec 21, 1956, p. 43.〕〔(CBS, 1956, VR-1000 in use photo from javeriana.edu.co )〕 On January 22, 1957, the NBC game show ''Truth or Consequences'', produced in Hollywood, became the first program to be broadcast in all time zones from a prerecorded videotape.〔"Daily N.B.C. Show Will Be on Tape", ''New York Times'', Jan. 18, 1957, p. 31.〕 ''The Edsel Show'', on October 13, 1957, was the first CBS entertainment program to be broadcast live to the nation from Hollywood, then tape-delayed for rebroadcast in the Pacific time zone. The engineers at Ampex who worked on the development of 2-inch quadruplex videotape from the Mark I to the VR-1000 were Charles Ginsburg,〔 Alex Maxey, Fred Pfost, Shelby Henderson, Charlie Anderson, and Ray Dolby (who later went on to found Dolby Laboratories).〔(terramedia.co.uk Ampex Team Photo 1956 )〕〔(Ampex Team Photo with Emmy from photobucket.com )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Quadruplex videotape」の詳細全文を読む スポンサード リンク
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