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The abbreviation NTSC can refer to the National Television System Committee,National Television System Committee (1951–1953), [Report 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.:5402138
Library of Congress Online Catalog
/ref> which developed the analog television color system that was introduced in North America in 1954 and stayed in use until digital conversion. NTSC is also commonly considered to be an abbreviation for the National Television Standards Committee, a subset of the National Television System Committee that was responsible for producing the detailed technical specifications for the transmission standard. It is one of three major analog color television standards, the others being PAL and SECAM. All the countries using NTSC are currently in the process of conversion, or have already converted to the ATSC standard, or to DVB, ISDB, or DTMB. This page primarily discusses the NTSC color encoding system. The articles on broadcast television systems and analog television further describe frame rates, image resolution, and audio modulation.

Geographic reach

The NTSC standard was used in most of North America, western South America, Liberia, Myanmar, South Korea, Taiwan, Philippines, Japan, and some Pacific island nations and territories (see map).

Digital conversion

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, with there being at least four different standards in use around the world. North America, parts of Central America, and South Korea are adopting or have adopted the ATSC standards, while other countries, such as Japan, are adopting or have adopted other standards instead of ATSC. After nearly 70 years, the majority of over-the-air NTSC transmissions in the United States ceased on January 1, 2010, and by August 31, 2011,DTV and Over-the-Air Viewers Along U.S. Borders
FCC.gov. Retrieved on 2014-05-11.
VideoHelp Forum Retrieved on 2015-01-23.
The majority of NTSC transmissions ended in Japan on July 24, 2011, with the Japanese prefectures of Iwate, Miyagi, and Fukushima ending the next year. After a pilot program in 2013, most full-power analog stations in Mexico left the air on ten dates in 2015, with some 500 low-power and repeater stations allowed to remain in analog until the end of 2016. 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

Technical details

Lines and refresh rate

NTSC color encoding is used with the System M television signal, which consists of  (approximately 29.97) interlaced frames of video per second. Each frame is composed of two fields, each consisting of 262.5 scan lines, for a total of 525 scan lines. 486 scan lines make up the visible raster. The remainder (the vertical blanking interval) allow for vertical synchronization and retrace. This blanking interval was originally designed to simply blank the electron beam of the receiver's CRT to allow for the simple analog circuits and slow vertical retrace of early TV receivers. However, some of these lines may now contain other data such as closed captioning and vertical interval timecode (VITC). In the complete raster (disregarding half lines due to interlacing) the even-numbered scan lines (every other line that would be even if counted in the video signal, e.g. ) are drawn in the first field, and the odd-numbered (every other line that would be odd if counted in the video signal, e.g. ) are drawn in the second field, to yield a flicker-free image at the field refresh frequency of  Hz (approximately 59.94 Hz). For comparison, 576i systems such as PAL-B/G and SECAM use 625 lines (576 visible), and so have a higher vertical resolution, but a lower temporal resolution of 25 frames or 50 fields per second. The NTSC field refresh frequency in the black-and-white system originally exactly matched the nominal 60 Hz frequency of alternating current power used in the United States. Matching the field refresh rate to the power source avoided intermodulation (also called ''beating''), which produces rolling bars on the screen. Synchronization of the refresh rate to the power incidentally helped kinescope cameras record early live television broadcasts, as it was very simple to synchronize a film camera to capture one frame of video on each film frame by using the alternating current frequency to set the speed of the synchronous AC motor-drive camera. When color was added to the system, the refresh frequency was shifted slightly downward by 0.1% to approximately 59.94 Hz to eliminate stationary dot patterns in the difference frequency between the sound and color carriers, as explained below in "Color encoding". By the time the frame rate changed to accommodate color, it was nearly as easy to trigger the camera shutter from the video signal itself. The actual figure of 525 lines was chosen as a consequence of the limitations of the vacuum-tube-based technologies of the day. In early TV systems, a master voltage-controlled oscillator was run at twice the horizontal line frequency, and this frequency was divided down by the number of lines used (in this case 525) to give the field frequency (60 Hz in this case). This frequency was then compared with the 60 Hz power-line frequency and any discrepancy corrected by adjusting the frequency of the master oscillator. For interlaced scanning, an odd number of lines per frame was required in order to make the vertical retrace distance identical for the odd and even fields, which meant the master oscillator frequency had to be divided down by an odd number. At the time, the only practical method of frequency division was the use of a chain of vacuum tube multivibrators, the overall division ratio being the mathematical product of the division ratios of the chain. Since all the factors of an odd number also have to be odd numbers, it follows that all the dividers in the chain also had to divide by odd numbers, and these had to be relatively small due to the problems of thermal drift with vacuum tube devices. The closest practical sequence to 500 that meets these criteria was . (For the same reason, 625-line PAL-B/G and SECAM uses , the old British 405-line system used , the French 819-line system used etc.)

Colorimetry

The original 1953 color NTSC specification, still part of the United States Code of Federal Regulations, defined the colorimetric values of the system as follows: Early color television receivers, such as the RCA CT-100, were faithful to this specification (which was based on prevailing motion picture standards), having a larger gamut than most of today's monitors. Their low-efficiency phosphors (notably in the Red) were weak and long-persistent, leaving trails after moving objects. Starting in the late 1950s, picture tube phosphors would sacrifice saturation for increased brightness; this deviation from the standard at both the receiver and broadcaster was the source of considerable color variation.

SMPTE C

Color encoding

Transmission modulation method

An NTSC television channel as transmitted occupies a total bandwidth of 6 MHz. The actual video signal, which is amplitude-modulated, is transmitted between 500 kHz and 5.45 MHz above the lower bound of the channel. The video carrier is 1.25 MHz above the lower bound of the channel. Like most AM signals, the video carrier generates two sidebands, one above the carrier and one below. The sidebands are each 4.2 MHz wide. The entire upper sideband is transmitted, but only 1.25 MHz of the lower sideband, known as a vestigial sideband, is transmitted. The color subcarrier, as noted above, is 3.579545 MHz above the video carrier, and is quadrature-amplitude-modulated with a suppressed carrier. The audio signal is frequency-modulated, like the audio signals broadcast by FM radio stations in the 88–108 MHz band, but with a 25 kHz maximum frequency deviation, as opposed to 75 kHz as is used on the FM band, making analog television audio signals sound quieter than FM radio signals as received on a wideband receiver. The main audio carrier is 4.5 MHz above the video carrier, making it 250 kHz below the top of the channel. Sometimes a channel may contain an MTS signal, which offers more than one audio signal by adding one or two subcarriers on the audio signal, each synchronized to a multiple of the line frequency. This is normally the case when stereo audio and/or second audio program signals are used. The same extensions are used in ATSC, where the ATSC digital carrier is broadcast at 0.31 MHz above the lower bound of the channel. "Setup" is a 54 mV(7.5 IRE) voltage offset between the "black" and "blanking" levels. It is unique to NTSC. CVBS stands for Color, Video, Blanking, and Sync.

Frame rate conversion

There is a large difference in frame rate between film, which runs at 24.0 frames per second, and the NTSC standard, which runs at approximately 29.97 (10 MHz×63/88/455/525) frames per second. In regions that use 25-fps television and video standards, this difference can be overcome by speed-up. For 30-fps standards, a process called "3:2 pulldown" is used. One film frame is transmitted for three video fields (lasting  video frames), and the next frame is transmitted for two video fields (lasting 1 video frame). Two film frames are thus transmitted in five video fields, for an average of  video fields per film frame. The average frame rate is thus 60 ÷ 2.5 = 24 frames per second, so the average film speed is nominally exactly what it should be. (In reality, over the course of an hour of real time, 215,827.2 video fields are displayed, representing 86,330.88 frames of film, while in an hour of true 24-fps film projection, exactly 86,400 frames are shown: thus, 29.97-fps NTSC transmission of 24-fps film runs at 99.92% of the film's normal speed.) Still-framing on playback can display a video frame with fields from two different film frames, so any difference between the frames will appear as a rapid back-and-forth flicker. There can also be noticeable jitter/"stutter" during slow camera pans (telecine judder). To avoid 3:2 pulldown, film shot specifically for NTSC television is often taken at 30 frame/s. To show 25-fps material (such as European television series and some European movies) on NTSC equipment, every fifth frame is duplicated and then the resulting stream is interlaced. Film shot for NTSC television at 24 frames per second has traditionally been accelerated by 1/24 (to about 104.17% of normal speed) for transmission in regions that use 25-fps television standards. This increase in picture speed has traditionally been accompanied by a similar increase in the pitch and tempo of the audio. More recently, frame-blending has been used to convert 24 FPS video to 25 FPS without altering its speed. Film shot for television in regions that use 25-fps television standards can be handled in either of two ways: * The film can be shot at 24 frames per second. In this case, when transmitted in its native region, the film may be accelerated to 25 fps according to the analog technique described above, or kept at 24 fps by the digital technique described above. When the same film is transmitted in regions that use a nominal 30-fps television standard, there is no noticeable change in speed, tempo, and pitch. * The film can be shot at 25 frames per second. In this case, when transmitted in its native region, the film is shown at its normal speed, with no alteration of the accompanying soundtrack. When the same film is shown in regions that use a 30-fps nominal television standard, every fifth frame is duplicated, and there is still no noticeable change in speed, tempo, and pitch. Because both film speeds have been used in 25-fps regions, viewers can face confusion about the true speed of video and audio, and the pitch of voices, sound effects, and musical performances, in television films from those regions. For example, they may wonder whether the Jeremy Brett series of Sherlock Holmes television films, made in the 1980s and early 1990s, was shot at 24 fps and then transmitted at an artificially fast speed in 25-fps regions, or whether it was shot at 25 fps natively and then slowed to 24 fps for NTSC exhibition. These discrepancies exist not only in television broadcasts over the air and through cable, but also in the home-video market, on both tape and disc, including laser disc and DVD. In digital television and video, which are replacing their analog predecessors, single standards that can accommodate a wider range of frame rates still show the limits of analog regional standards. The initial version of the ATSC standard, for example, allowed frame rates of 23.976, 24, 29.97, 30, 59.94, and 60 frames per second, but not 25 and 50. Modern ATSC allows 25 and 50 FPS.

Modulation for analog satellite transmission

Because satellite power is severely limited, analog video transmission through satellites differs from terrestrial TV transmission. AM is a linear modulation method, so a given demodulated signal-to-noise ratio (SNR) requires an equally high received RF SNR. The SNR of studio quality video is over 50 dB, so AM would require prohibitively high powers and/or large antennas. Wideband FM is used instead to trade RF bandwidth for reduced power. Increasing the channel bandwidth from 6 to 36 MHz allows a RF SNR of only 10 dB or less. The wider noise bandwidth reduces this 40 dB power saving by 36 MHz / 6 MHz = 8 dB for a substantial net reduction of 32 dB. Sound is on a FM subcarrier as in terrestrial transmission, but frequencies above 4.5 MHz are used to reduce aural/visual interference. 6.8, 5.8 and 6.2 MHz are commonly used. Stereo can be multiplex, discrete, or matrix and unrelated audio and data signals may be placed on additional subcarriers. A triangular 60 Hz energy dispersal waveform is added to the composite baseband signal (video plus audio and data subcarriers) before modulation. This limits the satellite downlink power spectral density in case the video signal is lost. Otherwise the satellite might transmit all of its power on a single frequency, interfering with terrestrial microwave links in the same frequency band. In half transponder mode, the frequency deviation of the composite baseband signal is reduced to 18 MHz to allow another signal in the other half of the 36 MHz transponder. This reduces the FM benefit somewhat, and the recovered SNRs are further reduced because the combined signal power must be "backed off" to avoid intermodulation distortion in the satellite transponder. A single FM signal is constant amplitude, so it can saturate a transponder without distortion.

Field order

An NTSC "frame" consists of an "even" field followed by an "odd" field. As far as the reception of an analog signal is concerned, this is purely a matter of convention and, it makes no difference. It is rather like the broken lines running down the middle of a road, it does not matter whether it is a line/space pair or a space/line pair; the effect to a driver is exactly the same. The introduction of digital television formats has changed things somewhat. Most digital TV formats store and transmit fields in pairs as a single digital frame. Digital formats that match NTSC field rate, including the popular DVD format, record video with the ''even field first'' in the digital frame, while the formats that match field rate of the 625 line system often record video with ''odd frame first''. This means that when reproducing many non-NTSC based digital formats it is necessary to reverse the field order, otherwise an unacceptable shuddering "comb" effect occurs on moving objects as they are shown ahead in one field and then jump back in the next. This has also become a hazard where non NTSC progressive video is transcoded to interlaced and vice versa. Systems that recover progressive frames or transcode video should ensure that the "Field Order" is obeyed, otherwise the recovered frame will consist of a field from one frame and a field from an adjacent frame, resulting in "comb" interlacing artifacts. This can often be observed in PC based video playing utilities if an inappropriate choice of de-interlacing algorithm is made. During the decades of high-power NTSC broadcasts in the United States, switching between the views from two cameras was accomplished according to two Field dominance standards, the choice between the two being made by geography, East versus West. In one region, the switch was made between the odd field that finished one frame and the even field that began the next frame; in the other, the switch was made after an even field and before an odd field. Thus, for example, a home VHS recording made of a local television newscast in the East, when paused, would only ever show the view from one camera (unless a dissolve or other multicamera shot were intended), whereas VHS playback of a situation comedy taped and edited in Los Angeles and then transmitted nationwide could be paused at the moment of a switch between cameras with half the lines depicting the outgoing shot and the other half depicting the incoming shot.

Variants

NTSC-M

Unlike PAL and SECAM, with its many varied underlying broadcast television systems in use throughout the world, NTSC color encoding is almost invariably used with broadcast system M, giving NTSC-M.

NTSC-N/NTSC50

NTSC-N/NTSC50 is an unofficial system combining 625-line video with 3.58 MHz NTSC color. PAL software running on an NTSC Atari ST displays using this system as it cannot display PAL color. Television sets and monitors with a V-Hold knob can display this system after adjusting the vertical hold.

NTSC-J

Only Japan's variant "NTSC-J" is slightly different: in Japan, black level and blanking level of the signal are identical (at 0 IRE), as they are in PAL, while in American NTSC, black level is slightly higher (7.5 IRE) than blanking level. Since the difference is quite small, a slight turn of the brightness knob is all that is required to correctly show the "other" variant of NTSC on any set as it is supposed to be; most watchers might not even notice the difference in the first place. The channel encoding on NTSC-J differs slightly from NTSC-M. In particular, the Japanese VHF band runs from channels 1–12 (located on frequencies directly above the 76–90 MHz Japanese FM radio band) while the North American VHF TV band uses channels 2–13 (54–72 MHz, 76–88 MHz and 174–216 MHz) with 88–108 MHz allocated to FM radio broadcasting. Japan's UHF TV channels are therefore numbered from 13 up and not 14 up, but otherwise uses the same UHF broadcasting frequencies as those in North America.

PAL-M (Brazil)

The Brazilian PAL-M system, introduced on February 19, 1972, uses the same lines/field as NTSC (525/60), and almost the same broadcast bandwidth and scan frequency (15.750 vs. 15.734 kHz). Prior to the introduction of color, Brazil broadcast in standard black-and-white NTSC. As a result, PAL-M signals are near identical to North American NTSC signals, except for the encoding of the color subcarrier (3.575611 MHz for PAL-M and 3.579545 MHz for NTSC). As a consequence of these close specs, PAL-M will display in monochrome with sound on NTSC sets and vice versa.

PAL-N

This is used in Argentina, Paraguay and Uruguay. This is very similar to PAL-M (used in Brazil). The similarities of NTSC-M and NTSC-N can be seen on the ITU identification scheme table, which is reproduced here: As it is shown, aside from the number of lines and frames per second, the systems are identical. NTSC-N/PAL-N are compatible with sources such as game consoles, VHS/Betamax VCRs, and DVD players. However, they are not compatible with baseband broadcasts (which are received over an antenna), though some newer sets come with baseband NTSC 3.58 support (NTSC 3.58 being the frequency for color modulation in NTSC: 3.58 MHz).

NTSC 4.43

OSKM

In January 1960 (7 years prior to adoption of the modified SECAM version) the experimental TV studio in Moscow started broadcasting using the OSKM system. The OSKM abbreviation means "Simultaneous system with quadrature modulation" (In Russian: Одновременная Система с Квадратурной Модуляцией). It used the color coding scheme that was later used in PAL (U and V instead of I and Q), because it was based on D/K monochrome standard, 625/50. The color subcarrier frequency was 4.4296875 MHz and the bandwidth of U and V signals was near 1.5 MHz. Only circa 4000 TV sets of 4 models (Raduga, Temp-22, Izumrud-201 and Izumrud-203) were produced for studying the real quality of TV reception. These TV's were not commercially available, despite being included in the goods catalog for trade network of the USSR. The broadcasting with this system lasted about 3 years and was ceased well before SECAM transmissions started in the USSR. None of the current multi-standard TV receivers can support this TV system.

NTSC-film

Film content commonly shot at 24 frames/s can be converted to 30 frames/s through the telecine process to duplicate frames as needed. :$\frac = \frac$ Mathematically for NTSC this is relatively simple as it is only needed to duplicate every fourth frame. Various techniques are employed. NTSC with an actual frame rate of   (approximately 23.976) frames/s is often defined as NTSC-film. A process known as pullup, also known as pulldown, generates the duplicated frames upon playback. This method is common for H.262/MPEG-2 Part 2 digital video so the original content is preserved and played back on equipment that can display it or can be converted for equipment that cannot.

Sometimes ''NTSC-U'', ''NTSC-US'', or ''NTSC-U/C'' is used to describe the video gaming region of North America (the U/C refers to US + Canada), as regional lockout usually restricts games from being playable outside the region.

Comparative quality

Reception problems can degrade an NTSC picture by changing the phase of the color signal (actually differential phase distortion), so the color balance of the picture will be altered unless a compensation is made in the receiver. The vacuum-tube electronics used in televisions through the 1960s led to various technical problems. Among other things, the color burst phase would often drift when channels were changed, which is why NTSC televisions were equipped with a tint control. PAL and SECAM televisions had no need of one, and although it is still found on NTSC TVs, color drifting generally ceased to be a problem for more modern circuitry by the 1970s. When compared to PAL in particular, NTSC color accuracy and consistency is sometimes considered inferior, leading to video professionals and television engineers jokingly referring to NTSC as ''Never The Same Color'', ''Never Twice the Same Color'', or ''No True Skin Colors'', while for the more expensive PAL system it was necessary to ''Pay for Additional Luxury''. PAL has also been referred to as ''Peace At Last'', ''Perfection At Last'' or ''Pictures Always Lovely'' in the color war. This mostly applied to vacuum tube-based TVs, however, and later-model solid state sets using Vertical Interval Reference signals have less of a difference in quality between NTSC and PAL. This color phase, "tint", or "hue" control allows for anyone skilled in the art to easily calibrate a monitor with SMPTE color bars, even with a set that has drifted in its color representation, allowing the proper colors to be displayed. Older PAL television sets did not come with a user accessible "hue" control (it was set at the factory), which contributed to its reputation for reproducible colors. The use of NTSC coded color in S-Video systems completely eliminates the phase distortions. As a consequence, the use of NTSC color encoding gives the highest resolution picture quality (on the horizontal axis and frame rate) of the three color systems when used with this scheme. (The NTSC resolution on the vertical axis is lower than the European standards, 525 lines against 625.) However, it uses too much bandwidth for over-the-air transmission. The Atari 800 and Commodore 64 home computers generated S-video, but only when used with specially designed monitors as no TV at the time supported the separate chroma and luma on standard RCA jacks. In 1987, a standardized four-pin mini-DIN socket was introduced for S-video input with the introduction of S-VHS players, which were the first device produced to use the four-pin plugs. However, S-VHS never became very popular. Video game consoles in the 1990s began offering S-video output as well. The mismatch between NTSC's 30 frames per second and film's 24 frames is overcome by a process that capitalizes on the ''field'' rate of the interlaced NTSC signal, thus avoiding the film playback speedup used for 576i systems at 25 frames per second (which causes the accompanying audio to increase in pitch slightly, sometimes rectified with the use of a pitch shifter) at the price of some jerkiness in the video. See Frame rate conversion above.

Vertical interval reference

Countries and territories that are using or once used NTSC

Experimented

* (Between 1962 and 1963, Rede Tupi and Rede Excelsior made the first unofficial transmissions in color, in specific programs in the city of São Paulo, before the official adoption of PAL-M by the Brazilian Government on February 19, 1972) * * (Experimented on 405-line variant of NTSC, then UK chose 625-line for PAL broadcasting.)

Countries and territories that have ceased using NTSC

The following countries and regions no longer use NTSC for terrestrial broadcasts.

* Broadcast television systems ** Advanced Television Systems Committee standards ** BTSC ** NTSC-J ** NTSC-C ** PAL ** RCA ** SECAM *Composite artifact colors *Dot crawl * List of common resolutions – Television * List of video connectors * Moving image formats * Oldest television station * Television channel frequencies ** Very high frequency ** Ultra high frequency ** Knife-edge effect ** Channel 1 (North American TV) ** Channel 37 ** North American broadcast television frequencies ** North American cable television frequencies ** Australasian TV frequencies * Broadcast-safe * Digital television transition in the United States * Glossary of video terms

Notes

References

* A standard defining the NTSC system was published by the International Telecommunication Union in 1998 under the title "Recommendation ITU-R BT.470-7, Conventional Analog Television Systems". It is publicly available on the Internet a
ITU-R BT.470-7
or can be purchased from th
ITU
* Ed Reitan (1997)