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NTSC, named after the National Television System Committee,〔National Television System Committee (1951–1953), (and Reports of Panel No. 11, 11-A, 12-19, with Some supplementary references cited in the Reports, and the Petition for adoption of transmission standards for color television before the Federal Communications Commission, n.p., 1953 ), 17 v. illus., diagrs., tables. 28 cm. LC Control No.:54021386 (Library of Congress Online Catalog )〕 is the analog television system that was used in most of the Americas (except Brazil, Argentina, Paraguay, Uruguay and French Guiana); Burma; South Korea; Taiwan; Japan; the Philippines;〔(NTSC system information and the countries that use it. ) High-Tech Productions〕 and some Pacific island nations and territories (see map). The first NTSC standard was developed in 1941 and had no provision for color. In 1953 a second NTSC standard was adopted, which allowed for color television broadcasting which was compatible with the existing stock of black-and-white receivers. NTSC was the first widely adopted broadcast color system and remained dominant until the 2010s, when it is gradually being replaced with different digital standards such as ATSC and others. Most countries using the NTSC standard, as well as those using other analog television standards, have switched to or are in process of switching to newer digital television standards, there being at least four different standards in use around the world. North America, parts of Central America, and South Korea are adopting the ATSC standards, while other countries are adopting or have adopted other standards. After nearly 70 years, the majority of over-the-air NTSC transmissions in the United States ceased on June 12, 2009,〔(Digital Television ). FCC.gov. Retrieved on 2014-05-11.〕 and by August 31, 2011〔(DTV and Over-the-Air Viewers Along U.S. Borders ). FCC.gov. Retrieved on 2014-05-11.〕 in Canada and most other NTSC markets.〔(Canada... PAL or NTSC? ). VideoHelp Forum Retrieved on 2015-01-23.〕 The majority of NTSC transmissions ended in Japan on July 24, 2011, while Mexico has complete digital simulcast since 2012, the same year as the cessation of NTSC broadcasts in the Japanese prefectures of Iwate, Miyagi, and Fukushima, but has as yet turned off all of its analog signals.〔〔(Televisión Digital Abierta (in Spanish) ) 2015 © Televisoras Grupo Pacífico. Retrieved 2015-11-06〕 Digital broadcasting allows higher-resolution television, but digital standard definition television continues to use the frame rate and number of lines of resolution established by the analog NTSC standard. ==History== The National Television System Committee was established in 1940 by the United States Federal Communications Commission (FCC) to resolve the conflicts that were made between companies over the introduction of a nationwide analog television system in the United States. In March 1941, the committee issued a technical standard for black-and-white television that built upon a 1936 recommendation made by the Radio Manufacturers Association (RMA). Technical advancements of the vestigial side band technique allowed for the opportunity to increase the image resolution. The NTSC selected 525 scan lines as a compromise between RCA's 441-scan line standard (already being used by RCA's NBC TV network) and Philco's and DuMont's desire to increase the number of scan lines to between 605 and 800.〔What actually occurred was the RCA TG-1 synch generator system was upgraded from 441 lines per frame, 220.5 lines per field, interlaced, to 525 lines per frame 262.5 lines per field, also interlaced, with minimal additional changes, particularly not those affecting the vertical interval which, in the extant RCA system, included "serrated" equalizing pulses bracketing the vertical synch pulse, itself being "serrated". For RCA/NBC, this was a ''very'' simple change from a 26,460 Hz master oscillator to a 31,500 Hz master oscillator, and minimal additional changes to the generator's divider chain. The "equalizing" pulses and the "serration" of the vertical synch pulse were necessary because of the limitations of the extant TV receiver video/synch separation technology, thought to be necessary because the synch was transmitted "in band" with the video, although at a quite different dc level. The early TV sets did not possess a "dc restorer" circuit, hence the need for this level of complexity. In-studio monitors were provided with separate horizontal and vertical synch, not "composite" synch and certainly not "in-band" synch (possibly excepting early color TV monitors, which were often driven from the output of the station's "colorplexer").〕 The standard recommended a frame rate of 30 frames (images) per second, consisting of two interlaced fields per frame at 262.5 lines per field and 60 fields per second. Other standards in the final recommendation were an aspect ratio of 4:3, and frequency modulation (FM) for the sound signal (which was quite new at the time). In January 1950, the Committee was reconstituted to standardize color television. In December 1953, it unanimously approved what is now called the ''NTSC'' color television standard (later defined as RS-170a). The "compatible color" standard retained full backward compatibility with existing black-and-white television sets. Color information was added to the black-and-white image by introducing a color subcarrier of precisely 3.579545 MHz (nominally 3.58 MHz). The precise frequency was chosen so that horizontal line-rate modulation components of the chrominance signal would fall exactly in between the horizontal line-rate modulation components of the luminance signal, thereby enabling the chrominance signal to be filtered out of the luminance signal with minor degradation of the luminance signal. Due to limitations of frequency divider circuits at the time the color standard was promulgated, the color subcarrier frequency was constructed as composite frequency assembled from small integers, in this case 5×7×9/(8×11) MHz.〔The master oscillator was 14.31818 MHz, from which the 3.579545 "color burst" frequency was obtained by dividing by four; and the 31 kHz "horizontal drive" and 60 Hz "vertical drive" were also synthesized from that frequency. This facilitated a conversion to color of the then common, but monochrome, RCA TG-1 synchronizing generator by the simple expedient of adding-on an external 14.31818 MHz temperature-controlled oscillator and a few dividers, and inputting the outputs of that chassis to certain test points within the TG-1, thereby disabling the TG-1's own 31500 Hz reference oscillator.〕 The horizontal line rate was reduced to approximately 15,734 lines per second (3.579545×2/455 MHz) from 15,750 lines per second, and the frame rate was reduced to approximately 29.970 frames per second (the horizontal line rate divided by 525 lines/frame) from 30 frames per second. These changes amounted to less than 0.1 percent and were readily tolerated by existing television receivers.〔"Choice of Chrominance Subcarrier Frequency in the NTSC Standards," Abrahams, I.C., Proc. IRE, Vol. 42, Issue 1, p.79-80〕〔"The Frequency Interleaving Principle in the NTSC Standards," Abrahams, I.C., Proc. IRE, vol. 42, Issue 1, p. 81-83〕 The FCC had briefly approved a different color television standard, starting in October 1950, which was developed by CBS.〔A third "line sequential" system from Color Television Inc. (CTI) was also considered. The CBS and final NTSC systems were called "field sequential" and "dot sequential" systems, respectively.〕 However, this standard was incompatible with black-and-white broadcasts. It used a rotating color wheel, reduced the number of scan lines from 525 to 405, and increased the field rate from 60 to 144, but had an effective frame rate of only 24 frames per second. Legal action by rival RCA kept commercial use of the system off the air until June 1951, and regular broadcasts only lasted a few months before manufacture of all color television sets was banned by the Office of Defense Mobilization (ODM) in October, ostensibly due to the Korean War.〔"Color TV Shelved As a Defense Step", ''The New York Times'', October 20, 1951, p. 1. "Action of Defense Mobilizer in Postponing Color TV Poses Many Question for the Industry", ''The New York Times'', October 22, 1951, p. 23. "TV Research Curb on Color Avoided", ''The New York Times'', October 26, 1951. Ed Reitan, (CBS Field Sequential Color System ), 1997. A variant of the CBS system was later used by NASA to broadcast pictures of astronauts from space.〕 CBS rescinded its system in March 1953,〔"CBS Says Confusion Now Bars Color TV," ''Washington Post'', March 26, 1953, p. 39.〕 and the FCC replaced it on December 17, 1953, with the NTSC color standard, which was cooperatively developed by several companies, including RCA and Philco.〔"F.C.C. Rules Color TV Can Go on Air at Once", ''The New York Times'', December 19, 1953, p. 1.〕 The first publicly announced network television broadcast of a program using the NTSC "compatible color" system was an episode of NBC's ''Kukla, Fran and Ollie'' on August 30, 1953, although it was viewable in color only at the network's headquarters.〔"NBC Launches First Announced Color Television Show", ''Wall Street Journal'', August 31, 1953, p. 4.〕 The first nationwide viewing of NTSC color came on the following January 1 with the coast-to-coast broadcast of the Tournament of Roses Parade, viewable on prototype color receivers at special presentations across the country. The first color NTSC television camera was the RCA TK-40, used for experimental broadcasts in 1953; an improved version, the TK-40A, introduced in March 1954, was the first commercially available color television camera. Later that year, the improved TK-41 became the standard camera used throughout much of the 1960s. The NTSC standard has been adopted by other countries, including most of the Americas and Japan. With the advent of digital television, analog broadcasts are being phased out. Most U.S. NTSC broadcasters were required by the FCC to shut down their analog transmitters in 2009. Low-power stations, Class A stations and translators are required to shut down by 2015. 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「NTSC」の詳細全文を読む スポンサード リンク
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