NTSC (an acronym of National Television System Committee) was the first American standard for analog television, published and adopted in 1941. It was one of three major color formats for analog television; the others were PAL and SECAM. NTSC color was usually associated with System M, and this combination was sometimes called NTSC II. A second NTSC standard was adopted in 1953, which allowed color television compatible with the existing stock of black-and-white sets. The EIA defined NTSC performance standards in EIS-170 (also known as RS-170) in 1957. The term "NTSC" has referred to digital formats with 480–487 active lines and a 30 or 29.97 FPS frame rate since the introduction of digital sources such as DVDs, and is a digital shorthand for System M. The NTSC-film standard has a digital resolution of 720 × 480 pixels for DVD-Videos, 480 × 480 pixels for Super Video CDs (SVCD, aspect ratio 4:3) and 352 × 240 pixels for Video CDs (VCD). The digital video (DV)-camcorder format equivalent of NTSC is 720 × 480 pixels. The digital television (DTV) equivalent is 704 × 480 pixels.
History
The NTSC was established in 1940 by the United States Federal Communications Commission (FCC) to resolve conflicts between companies about the introduction of a nationwide analog television system. In March 1941, the committee issued a technical standard for black-and-white television based on a 1936 recommendation by the Radio Manufacturers Association (RMA). Technical advancements of the vestigial sideband technique provided an opportunity to increase image resolution. The NTSC selected 525 scan lines as a compromise between RCA's 441-scan line standard (used by RCA's NBC TV network) and Philco and DuMont's desire to increase the number of scan lines to between 605 and 800. The standard recommended a frame rate of 30 FPS, 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) of the sound signal. In January 1950, the committee was reconstituted to standardize color television. The FCC had briefly approved a 405-line field-sequential color TV standard, developed by CBS, in October 1950. The CBS system was incompatible with existing black-and-white sets. 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 with an effective frame rate of 24 fps. 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 the manufacture of all color sets was banned by the Office of Defense Mobilization in October (ostensibly due to the Korean War). A variant of the CBS system was later used by NASA to broadcast pictures of astronauts in space. CBS rescinded its system in March 1953, and the FCC replaced it on December 17 of that year with an NTSC color standard developed by several companies (including RCA and Philco). In December 1953, the FCC unanimously approved what became the NTSC color-television standard (later defined as RS-170a). The standard retained backward compatibility with existing black-and-white sets. Color information was added to the black-and-white image by introducing a color subcarrier of 315⁄88 MHz (3.579545 MHz ± 10 Hz). This frequency was chosen so horizontal line-rate modulation components of the chrominance signal fall between the horizontal line-rate modulation components of the luminance signal; the chrominance signal could be easily filtered out of the luminance signal on new sets, and would be minimally visible on existing sets. Due to limitations of frequency divider circuits when the color standard was promulgated, the color subcarrier frequency was constructed as a composite frequency assembled from small integers – in this case, 5 × 7 × 9 MHz divided by 8 × 11. The horizontal line rate was reduced to 15,734 lines per second (3.579545 MHz × 2 ÷ 455 = 9⁄572 MHz) from 15,750 lps, and the frame rate was reduced to 30/1.001 ≈ 29.970 fps (the horizontal line rate divided by 525 lines/frame) from 30 fps. The changes amounted to 0.1 percent, and were tolerated by existing TV sets. 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, viewable in color only at NBC headquarters. The first nationwide viewing of NTSC color was 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 nationwide. 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, an improved TK-41 became the standard camera and was used through much of the 1960s. The NTSC standard was adopted by other countries, including Japan and several in the Americas.
Digital conversion With the advent of digital television, analog broadcasts were largely phased out. NTSC broadcasters in the U.S. were required by the FCC to shut down their analog transmitters by February 17, 2009; the shutdown was later moved to June 12 of that year. Low-power and Class A stations and translators were required to shut down by 2015, although an FCC extension allowed some stations operating on Channel 6 to operate until July 13, 2021. Canadian analog TV transmitters in markets not subject to the mandatory 2011 transition were to be shut down by January 14, 2022, under a 2017 schedule from Innovation, Science and Economic Development Canada. Most countries using the NTSC standard and those using other analog television standards have switched (or are switching) to newer digital television standards; at least four different standards are in use worldwide. North America, parts of Central America, and South Korea are adopting (or have adopted) the ATSC standards; other countries, such as Japan, are adopting (or have adopted) standards other than ATSC. Most over-the-air NTSC transmissions in the United States ended on June 12, 2009, and by August 31, 2011, in Canada and most other NTSC markets.
Technical details
Colorimetry
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