What is pal secam ntsc. All about video standards NTSC, PAL and SECAM

PAL, SECAM and NTSC- these are systems in which a signal is broadcast from an antenna, cable receiver, satellite receiver or DVD.

PAL, SECAM and NTSC- These are systems of chromaticity or color transmission. If they are incompatible between the signal source and the TV, the picture on the screen will be black and white, or may be narrowed or striped without a standard image. The signal itself, which the TV circuit processes, contains information about brightness And chromaticity. Color information is encoded into one of the systems PAL, SECAM...

To get a color image, only three colors are enough: red , blue And green. Therefore, the television signal must contain information about these three colors and the signal brightness.

Knowing the brightness information Y, as well as the blue signal IN colors and red R, you can, through a simple calculation, find out information about the color green G.

• NTSC
  As signals for transmitting color information in the system NTSC accepted color difference signals (R-Y And B-Y). The transmission of these signals is carried out in the spectrum of the brightness signal at one color subcarrier frequency, with a phase shift of 90 degrees.

  There are several standards NTSC, the most popular of which are: NTSC 4.43 And NTSC 3.58. They all have a half frame rate 60Hz(more precisely: 59.94005994 Hz), number of lines: 525 (486 - active), and the numbers: 4.43 or 3.58 - this is the frequency at which color information is transmitted (modulation frequency)

  The main disadvantage of the system is the possibility of distortions in color transmission. They cause the color tone on the TV screen to change depending on the brightness of a given area of ​​the image. For example, human faces on screen appear reddish in the shadows and greenish in the highlights. To reduce this distortion, TVs NTSC equipped with color tone regulators: TINT CONTROL. This control allows you to achieve a more natural coloring of details with a certain brightness, but the distortion of the color tone of the brighter or darker areas of the image even increases.

• PAL
  PAL- an analog color television system, developed by an engineer from a German company and presented as a television broadcasting standard. System PAL is the main color television system in Europe.

  Main characteristics: half-frame change frequency - 50 Hz, number of lines - 625 (576 active), color subcarrier (color information) modulation frequency 4.43 MHz

  Since the number of complete frames in PAL equals 25 (per second) - this is close to 24 - standard filming frames, therefore, the process of transferring film films to the PAL television standard is as simple and convenient as possible (no need to trick extra non-existent frames, as for NTSC)

  Adding the voltage at the input of the delay line with the inverted voltage at its output eliminates the phase error (failure) and the color gamut on the TV screen looks more natural than when watching programs encoded in NTSC.

  Variety of standard PAL-60, supports a field change frequency of 60 Hz, adopted in the NTSC system, so it can work on equipment and televisions that have this frame rate.

• SECAM
  The main advantage of the system SECAM is the absence of cross-distortion between color difference signals, achieved through their sequential transmission. However, in practice, this advantage may not always be realized due to the imperfection of the color signal switches in the decoding device. System SECAM practically insensitive to differential phase distortion, especially critical for the NTSC system. Due to the use of frequency modulation, there is high resistance to changes in the amplitude of the subcarrier that arise due to the unevenness of the phase-frequency response of the transmission path. The NTSC system is more sensitive to such distortion, which manifests itself as a change in color saturation. For the same reasons SECAM less sensitive to variations in video tape speed.

  Several modifications of the standard are used around the world SECAM, which do not differ from each other in the way they transmit color difference signals, including so-called pre-emphasis. Only the carrier frequencies of the luminance video signal, audio and the method of sound modulation differ. One of the important differences now is the method of color recognition. For this purpose, they can be used as standard color recognition signals SECAM, and bursts of subcarrier pulses during horizontal blanking.

• MESECAM
  MESECAM- is a type of system SECAM and serves to ensure that VCRs operating in the PAL standard have the ability to record programs broadcast in the SECAM system. It was not the best, but a fairly simple and inexpensive development, the need for which arose with the massive distribution of VCRs in the countries of Eastern Europe (USSR) and Asia, which received television signals in the SECAM system
• HDTV
  HDTV (High Definition Television) is a new direction in the development of television in the world. Name in Russian - high definition television (HDTV).

Regular television assumes an image resolution of 720 by 576 pixels, and HDTV allows you to watch television programs with a resolution of up to 1920 by 1080 pixels. So the image size HDTV 5 times more than in regular television, or we can say that HDTV five times clearer than regular TV.

Another feature of the standard HDTV is that it regulates 60 progressive frames per second, while conventional TV provides only 24 (25) frames per second. This number of frames allows you to get a much softer and more natural image on the screen, especially in dynamic scenes.

The term “High Definition” appeared in the 30s of the 20th century. It was then that a qualitative leap occurred in television: systems began to be used that made it possible to abandon images with a resolution of 15 - 200 lines. In the mid-50s, the first prototypes were created. However, in order for high-definition television to become visible to the naked eye, a display with a large screen diagonal is required. The high cost of such displays hampered development HDTV for decades. Rapid development HDTV began in the mid-2000s, simultaneously with the widespread adoption of plasma and liquid crystal displays.

· 720p: 1280×720 pixels, progressive scan, aspect ratio 16:9, frequency - 24, 25, 30, 50 or 60 frames per second (this HDTV format is recommended as standard for EBU member countries);

· 1080i: 1920×1080 pixels, interlaced scanning, aspect ratio 16:9, frequency - 50 or 60 fields per second;

· 1080p: 1920x1080 pixels, progressive scan, 16:9 aspect ratio, 24, 25 or 30 frames per second.

To view HDTV movies you need HDTV TV. It could be HDTV plasma, LCD TV or HDTV projector. You can also watch on a monitor (LCD or CRT), but of all quality HDTV You won't see. Also, you need a player with support HDTV, or a powerful computer. If you want to enjoy HDTV television at home, you need to purchase a special receiver and satellite dish.

If you decide to purchase a camera abroad, especially in the US and Japan, be extremely careful. Prices in these countries are extremely attractive, only all video equipment is designed to work in NTSC (however, especially for Russian tourists there are stores selling electronics in the PAL system, but here you need to be doubly vigilant).

In this regard, it makes sense to delve deeper into the concept of such abbreviations as NTSC, PAL, SECAM

What does NTSC mean?

NTSC is abbreviated. English National Television Standards Committee - National Television Standards Committee is an analog color television system developed in the USA. On December 18, 1953, color television broadcasting using this particular system was launched for the first time in the world. NTSC has also been adopted as the standard color television system in Canada, Japan and a number of countries on the American continent.

Technical Features of NTSC

• number of fields - 60 Hz (more precisely 59.94005994 Hz);
• number of lines (resolution) - 525;
• subcarrier frequency - 3579545.5 Hz.
• number of frames per second - 30.
• Beam scanning is interlaced (interlacing).

What does PAL mean?

PAL is abbr. from English phase-alternating line is an analogue color television system developed by Walter Bruch, an engineer at the German company Telefunken, and introduced as a television broadcasting standard in 1967.

Like all analog television standards, PAL is adapted and compatible with older monochrome (black and white) television broadcasting. In adapted analogue color television standards, an additional color signal is transmitted at the end of the monochrome television signal spectrum.

As is known from the nature of human vision, the sensation of color consists of three components: red (R), green (G) and blue (B). This color model is abbreviated RGB. Due to the predominance of the green color component in the average television picture and to avoid redundant coding, the difference between R-Y and B-Y is used as an additional color signal (Y is the overall brightness of a monochrome television signal). The PAL system uses the YUV color model.

Both additional chrominance signals in the PAL standard are transmitted simultaneously in quadrature modulation (a variation of AM), the typical subcarrier frequency is 4433618.75 Hz (4.43 MHz).

In this case, each color difference signal is repeated in the next line with a phase rotation of 15.625 kHz by 180 degrees, due to which the PAL decoder completely eliminates phase errors (typical of the NTSC system). To eliminate the phase error, the decoder adds the current line and the previous one from memory (analogue television receivers use a delay line). Thus, objectively, a color television image in the PAL standard has half the vertical resolution of a monochrome image.

Subjectively, due to the greater sensitivity of the eye to the brightness component, such deterioration is almost not noticeable in average pictures. The use of digital signal processing further mitigates this disadvantage.

What does SECAM mean?

SECAM is abbr. from fr. Séquentiel couleur avec mémoire, later Séquentiel couleur à mémoire - sequential color with memory - an analogue color television system first used in France. Historically, it is the first European color television standard.

The color signal in the SECAM standard is transmitted in frequency modulation (FM), one color component in one television line, alternately. The previous R-Y or B-Y signal is used as the missing lines, respectively, receiving it from memory (in analog television receivers a delay line is used for this). Thus, objectively, a color television image in the SECAM standard has half the vertical resolution of a monochrome image. Subjectively, due to the greater sensitivity of the eye to the brightness component, such deterioration is almost not noticeable in average pictures. The use of digital signal processing further mitigates this disadvantage.

As a joke, it is customary to decipher the abbreviation SECAM as “System Essentially Contrary to AMerican” (a system essentially opposite to the American one).

By the way, video cassettes marked NTSC do not correspond to the PAL system in terms of quality and recording duration.

2 years ago

Television standards NTSC PAL SECAM D2-MAC
Worldwide television broadcasting has a number of standards for color coding and the organization of transmission of audio signals and synchronization. They are a combination of three color coding systems (NTSC, PAL, SECAM) and ten signal transmission and scanning standards: B, G, D, K, H, I, KI, N, M, L.

Note:
standards B and G; D and K differ in the frequency values ​​of TV channels (MV and UHF, respectively).
The video signal modulation polarity is “-” negative, “+” positive.
Since interlaced scanning is used when “drawing” an image, the true frame rate is half as low as the frame rate—the frequency at which half-frames (fields) change.

* To be precise, the frequency of the fields is 58.94 Hz.

Currently, three compatible color television systems are in operation - SECAM, HTSC and PAL. Regardless of the type of system, signal sensors (TV cameras) generate signals of three primary colors: Er - red, Eg - green and Ed - blue. The same signals control the beam currents in the electronic projectors of the kinescope on the TV. By changing the ratio of signals at the cathodes of the kinescope, you can obtain any color tone within the color triangle determined by the color coordinates of the phosphors used.
The differences between color television (CT) systems are in the methods of obtaining the so-called full color video signal (PCTS) from primary color signals, which modulates the carrier frequency in the television transmitter.
This conversion is necessary in order to place information about the color image in the frequency band of the black and white signal. This compaction of signal spectra is based on a feature of the human visual system, which consists in the fact that small details of the image are perceived as uncolored.
The primary color signals are converted into a wideband brightness signal Ey, corresponding to a black-and-white television video signal, and three narrowband signals carrying color information.
These are the so-called color difference signals. They are obtained by subtracting the brightness signal from the corresponding primary color signal.
The brightness signal is obtained by adding in a certain proportion three signals of primary colors: Ey= rEr+gEg+bEb (*) In all color television systems, only brightness signals Ey and two color difference signals, Er-y and Eb-y, are transmitted. The Eg-y signal is restored in the receiver from the expression (*). (It should be noted that before mixing, the signals of primary colors go through gamma correction circuits that compensate for distortions caused by the nonlinear dependence of the brightness of the screen on the amplitude of the modulating signal).
NTSC system The NTSC system is the first central heating system that has found practical application. Developed in the USA and adopted for broadcasting in 1953. When creating the HTSC system, the basic principles of color image transmission were developed, which were used to one degree or another in all subsequent systems.
In the HTSC system, the PCTS contains in each line a luminance component and a chrominance signal, transmitted using a subcarrier lying in the frequency band of the luminance signal. The subcarrier is modulated in each line by two chrominance signals Er-y and Eb-y. To prevent color signals from creating mutual interference, the HTSC system uses quadrature balanced modulation.
There are two main values ​​for the HTSC chrominance subcarrier: 3.579545 and 4.43361875 MHz. The second value is minor and is used mainly in video recording to use a recording-playback channel common with the PAL system.
The HTSC system has a number of advantages: - high color clarity with a relatively narrow-band transmission channel; The structure of the signal spectra makes it possible to effectively separate information using comb digital filters. The HTSC decoder is relatively simple and does not contain a delay line.
At the same time, the HTSC system also has disadvantages, the main one of which is its high sensitivity to signal distortion in the transmission channel.
Signal distortion in the form of amplitude modulation (AM) is called differential distortion. As a result of such distortions, the color saturation of bright and dark areas turns out to be different. These distortions cannot be eliminated using the automatic gain control (AGC) circuit of the chrominance signal, since differences in the amplitude of the color subcarrier appear within a single line.
Distortions in the form of phase modulation of the color subcarrier by the brightness signal are called differential phase distortions. They cause changes in color tone depending on the brightness of a given area of ​​the image.
For example, human faces are colored reddish in the shadows and greenish in illuminated areas.
To reduce the noticeability of d-f distortions, HTSC televisions provide an operational color tone controller, which allows you to create a more natural coloring of parts with the same brightness. However, distortion of the color tone of brighter or darker areas increases.
High requirements for transmission channel parameters lead to more complex and expensive HTSC equipment or, if these requirements are not met, to a decrease in image quality.
The main goal in developing the PAL and SECAM system was to eliminate the shortcomings of the HTSC system.
PAL system The PAL system was developed by Telefunken in 1963. The purpose of its creation was the disadvantage that later became clear, HTSC - sensitivity to differential phase distortion. What the PAL system has is obvious.
a number of advantages that were not initially apparent. In the PAL system, as in HTSC, quadrature modulation of the color subcarrier with chrominance signals is used. But if in the HTSC system the angle between the total vector and the B-Y vector axis, which determines the color tone when transmitting the color field, is constant, then in the PAL system its sign changes every line. Hence the name of the system - Phase Alternation Line.
Reducing sensitivity to differential phase distortion is achieved by averaging color signals in two adjacent lines, which leads to a twofold decrease in vertical color clarity compared to HTSC. This feature is a disadvantage of the PAL system.
Advantages: low sensitivity to diff-phase distortion and asymmetry of the color channel passband. (The latter property is especially valuable for countries where the G standard has been adopted with a separation of image and sound carriers of 5.5 MHz, which always causes a limitation of the upper sideband of the color signal.)
The PAL system also has a gain in signal/noise ratio of 3dB relative to HTSC.
PAL60 - HTSC video playback system. In this case, the HTSC signal is easily transcoded into PAL, but the number of fields remains the same (that is, 60). The TV must support this frame rate value.

SECAM system The SECAM system in its original form was proposed in 1954. French inventor Henri de France. The main feature of the system is the alternate transmission of color-difference signals through a line with further restoration of the missing signal in the receiver using a delay line for the time of the line interval.
The name of the system is formed from the initial letters of the French words SEquentiel Couleur A Memoire (alternate colors and memory). In 1967, broadcasting on this system began in the USSR and France.
Color information in the SECAM system is transmitted using frequency modulation of the color subcarrier. The rest frequencies of the subcarriers in lines R and B are different and are Fob=4250 kHz and For=4406.25 kHz.
Since in the SECAM system, color signals are transmitted alternately through a line, and in the receiver they are restored using a delay line, i.e. information from the previous line is repeated, then the vertical color clarity is halved, as in the PAL system.
The use of FM provides low sensitivity to the effects of “differential gain” type distortions. The sensitivity of SECAM and to diff-phase distortions is low. In color fields, where the brightness is constant, these distortions do not appear in any way. At color transitions, a spurious increment in the subcarrier frequency occurs, which causes them to be delayed. However, when the transition duration is less than 2 μs, the correction circuits in the receiver reduce the effects of these distortions.
Usually, after the bright areas of the image, the edging is blue, and after the dark areas, it is yellow. The tolerance for differential phase distortion is about 30 degrees, i.e. 6 times wider than in HTSC.

D2-MAC system In the late 70s, improved color television systems were developed using time division compression of the luminance and chrominance components. These systems are the basis for high-definition television (HDTV) systems, and are called MAK (MAC) - “Multiplexed Analog Components”.
In 1985, France and Germany agreed to use one of the modifications of the MAC systems, namely D2-MAC / Paket, for satellite broadcasting.
Main features: the initial line interval of 10 microseconds is reserved for the transmission of digital information: line synchronization signal, audio and teletext. The digital package uses binary coding using a three-level signal, which halves the required bandwidth of the communication channel.
This coding principle is reflected in the name - D2. Two stereo audio channels can be transmitted simultaneously.
The rest of the line is occupied by analog video signals. First, the compressed line of one of the color-difference signals (17 μs) is transmitted, then the luminance line (34.5 μs). The principle of color coding is approximately the same as in SECAM. To transmit a complex D2-MAC signal, a channel with a bandwidth of 8.4 MHz is required.
The D2-MAC system provides significantly better color image quality than all other systems. The image is free of interference from color subcarriers, there is no crosstalk between the luminance and chrominance signals, and image clarity is noticeably improved.