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Videotape
Videotape is magnetic tape used for storing motion images and usually sound, as opposed to film or random-access digital media. Videotapes are also used for storing scientific or medical data, such as the data produced by an electrocardiogram. In most cases, a helical-scan video head rotates against the moving tape to record the data in two dimensions, because video signals have a very high bandwidth, and static heads would require extremely high tape speeds. Videotape is used in both video tape recorders (VTRs) or, more commonly and more recently, videocassette recorders (VCRs) and camcorders. Tape is a linear method of storing information, and since nearly all video recordings made nowadays are recorded to random-access media such as a hard disk or flash storage, videotape is expected to gradually lose importance as nonlinear/random-access methods of storing digital video data become more common.
Information stored can be in the form of either an analog signal or digital signal.
== Early formats ==
The electronics division of entertainer Bing Crosby's production company, Bing Crosby Enterprises (BCE), gave the world's first demonstration of a videotape recording in Los Angeles on November 11, 1951. Developed by John T. Mullin and Wayne R. Johnson since 1950, the device gave what were described as "blurred and indistinct" images using a modified Ampex 200 tape recorder and standard quarter-inch (0.6 cm) audio tape moving at 360 inches (9.1 m) per second.〔"Tape Recording Used by Filmless 'Camera', ''The New York Times'', Nov. 12, 1951, p. 21.〕〔Eric D. Daniel, C. Denis Mee, and Mark H. Clark (eds.), ''Magnetic Recording: The First 100 Years'', IEEE Press, 1998, p. 141. ISBN 0-07-041275-8〕 A year later, an improved version using one-inch (2.6 cm) magnetic tape was shown to the press, who reportedly expressed amazement at the quality of the images although they had a "persistent grainy quality that looked like a worn motion picture". Overall the picture quality was still considered inferior to the best kinescope recordings on film.〔"Tape-Recorded TV Nears Perfection", ''The New York Times'', Dec. 31, 1952, p. 10.〕 Bing Crosby Enterprises hoped to have a commercial version available in 1954 but none came forth.〔"New Deal on TV Seen at Parley", ''The New York Times'', May 1, 1953, p. 30.〕 BCE demonstrated a color model in February 1955 using a longitudinal recording on half-inch (1.3 cm) tape, essentially similar to what RCA had demonstrated in 1953 (see below). CBS, RCA's competitor, was about to order BCE machines when Ampex introduced the superior Quadruplex system (see below).〔Daniel et al., p. 148. BCE was acquired by 3M Company in 1956.〕
RCA demonstrated the magnetic tape recording of both black-and-white and color television programs at its Princeton laboratories on December 1, 1953.〔"Magnetic Tape Used By RCA to Photograph Television Program", ''The Wall Street Journal'', Dec. 2, 1953, p. 1.〕〔"(Color TV on Tape )", ''Popular Mechanics'', April 1954, p. 157.〕 The high-speed longitudinal tape system, called Simplex, in development since 1951, can record and play back only a few minutes of a television program. The color system used half-inch (1.3 cm) tape to record five tracks—one each for red, blue, green, synchronization, and audio. The black-and-white system used quarter-inch (0.6 cm) tape with two tracks, one for analog video and one for sound. Both systems ran at 360 inches (9.1 m) per second.〔Stewart Wolpin, ("The Race to Video" ), ''Invention & Technology'', autumn 1994.〕 RCA-owned NBC first used it on ''The Jonathan Winters Show'' on October 23, 1956 when a prerecorded song sequence by Dorothy Collins in color was included in the otherwise live television program.〔"(TV Goes to Tape )", ''Popular Science'', Feb. 1960, p. 238.〕〔Ed Reitan, (RCA-NBC Firsts in Color Television (commented) ).〕 The BBC experimented from 1952 to 1958 with a high-speed linear videotape system called VERA, but this was ultimately unfeasible. It used half-inch (1.27 cm) tape traveling at 200 inches (5.08 m) per second.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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