What is pal secam ntsc. What is accepted as a standard in Russia: PAL, SECAM, NTSC? What does "SECAM" mean?


I bet many have heard the terms PAL, SECAM and NTSC. Televisions and TV tuners, in the process of setting up channels, often suffer from questions about choosing one of them. The situation gets worse when it additionally offers several subtypes of any of the three formats to choose from. So what should you choose? And most importantly, how do all these formats differ from each other? We will now look into all this.

There are three systems in the world analog color television - NTSC, PAL And SECAM, similar in many ways, and at the same time, differing in a number of parameters. This situation often requires the use of special decoders to convert video recordings from one standard to another.

A television picture consists of lines (lines) sequentially displayed on the screen. Similar method image formation is called line scan, and the cycle of complete image (frame) change is personnel scanning. How more lines on the screen, the better the vertical clarity of the image, and the increased frame rate eliminates the possible flickering effect.

The figure shows the predominant use of color TV standards by region.

Basic parameters of TV signals

Due to limited bandwidth communication channels, each frame in all TV standards is transmitted in two steps or, as they say, consists of two fields. Initially (in the first field) even lines are displayed, then odd ones. This scanning is called interlaced and, unlike horizontal scanning, it somewhat degrades the image quality, but allows the TV signal to fit into the standard frequency band of communication channels.

The frequency spectrum of a complete color TV signal is shown in the figure, from which it can be seen that the TV signal consists of brightness, color and sound signals transmitted over communication channels using separate carrier frequencies. The main differences between the standards are in the way color is encoded based on modulation of the carrier frequency of the color signal.

When displaying a received television signal, the color component is superimposed on the brightness component. Therefore, when using equipment that does not support one or another standard, it is usually possible to obtain at least a black and white picture. The audio carrier frequency can be different even in variants of the same standard, which is sometimes the reason for the lack of sound during normal video playback.

NTSC

This color television standard ( NTSC) developed in the USA. The first version appeared in 1941, and regular television broadcasts began in 1954. In development NTSC The largest electronic companies at the time, members of the National Committee on Television Systems, took part. National Television System Committee(NTSC)). Currently standard NTSC used in most of the Americas, as well as in Japan, South Korea, in Taiwan and the Philippines.

Two options are widely used NTSC, denoted by the letter indices M and N. Historically, the first was, and is now the most common version, NTSC M. Then NTSC N (sometimes called PAL N) appeared, today used in some countries South America. True, NTSC J also works in Japan, but this option differs slightly from the main one - NTSC M.

Main characteristics of the NTSC format

The horizontal scanning frequency for NTSC M is 525 lines per screen, the frame rate is 30. The frequency band occupied by the video signal is 4.2 MHz. NTSC N uses slightly more lines - 625 and a lower frame rate - 25 Hz.

System based NTSC allows to provide high quality color images, but imposes very stringent requirements on receiving and transmitting equipment. Due to the peculiarities of signal formation in this format, during decoding it is not always possible to completely separate the signal into individual components, so color signals are mixed with brightness. And, depending on the brightness of the image area, it may slightly change its color tone.

Phase distortions of the signal that sometimes occur during transmission also contribute to not entirely natural transmission color tone, and amplitude-frequency ones cause a change in color saturation.

PAL

Standard PAL(English) Phase Alternation Line) was first used in 1967 in Germany and the UK. Broadcasting in these countries began in slightly different versions, which have now become even more numerous. PAL is widely used in most countries Western Europe, Africa, Asia, Australia and New Zealand.

In fact, PAL is an advanced NTSC system that eliminates the sensitivity of the transmitted signal to phase distortion by changing the method of modulating the color carrier frequency. True, this led to some deterioration in clarity, which is partly compensated (in some versions of the standard) by an increased number of lines.

The PAL standard has greatest number varieties used.

SECAM

Standard SECAM(French) Sequential Couleur Avec Memoire) - sequential color transmission with memory was developed in France. Regular broadcasting using it began in 1967, in France and the USSR. IN SECAM 625 lines are used at 25 frames, or 50 fields per second. Now SECAM used in France and some European countries, some former CCCP countries and Africa.

The peculiarity of the system is that color difference signals are transmitted via frequency modulation. Whereas PAL and NTSC use quadrature amplitude modulation. Frequency modulation, as well as alternate (through the line) transmission of two color signals, made it possible to get rid of excessive sensitivity to distortion, but somewhat deteriorated the clarity, which, however, in reception conditions terrestrial television not always fundamental and most noticeable in cable systems. SECAM allows you to achieve more natural color rendering due to improved separation of color signals from brightness.

For recording on magnetic tape, a type of standard was used - MESECAM, in which the subcarriers of color difference signals are moved to more low frequencies(approximately 1.1 MHz), which minimized the impact of variable tape speed on color quality.

Comparison of formats

A list of the main differences between the standards is summarized in the table. As can be seen, there are significant differences in carrier frequencies and the total frequency band occupied in communication channels.

Standard NTSC M PAL B,G,H PAL I PAL N PAL M SECAM B,G,H SECAM D,K,L
Number of lines/frames 525/30 625/25 625/25 625/25 525/30 625/25 625/25
Video signal frequency band, MHz 4,2 5 5,5 4,2 4,2 5 6
Color carrier, MHz 3,58 4,43 4,43 3,58 3,58 4.25 and 4.406 4.25 and 4.406
Sound carrier, MHz 4,5 5,5 6 4,5 4,5 5,5 6,5

However, today it is unlikely that readers will have to suffer seriously due to problems and incompatible formats. No matter how you output video from your computer, you will almost always be able to choose from at least two formats PAL or NTSC.

PAL, SECAM and NTSC- these are systems in which a signal is broadcast (from an antenna, cable, satellite receiver or DVD). The most important thing you need to know about them and a little history in our article

About what it is PAL or SECAM Most of us found out only in the late 80s, when we brought with us from abroad or bought the first imported video recorders, video players and video cassettes with films or music in company stores. What a disappointment it was when it turned out that it was not so easy to connect them to our Soviet televisions, and having connected them, it turned out that the picture was black and white. Then, turning to the master, the owner of the video camera learned that his television only received the system colors " SECAM", and all the videotapes he bought were recorded in " PAL"or, even worse, in one of the standards" NTSC"

Speaking in simple language, PAL, SECAM and NTSC- These are systems of “chromaticity” or color transmission. If they do not match (at the signal source and the TV), the picture on the screen will be black and white (and it may also be narrowed or even stripes instead of a picture). The signal itself, which the TV circuit processes, contains information about brightness(black and white picture) and chromaticity(about how a b/w picture needs to be colored). So, information about the color of “paints” is precisely encoded into one of the PAL, SECAM systems...

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 have stripes without 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 obtain color image, just three colors are enough: red , blue And green. That's why, 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 the screen appear reddish in the shadows and greenish in the illuminated areas. 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 AFC 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. The only differences are the carrier frequencies of the luminance video signal, audio, and the method of sound modulation. One of important differences is currently a color recognition method. For this they can be used as standard signals color recognition 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 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 to high definition television has become noticeable 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 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 accepted as standard system color television also 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 - an analogue color television system, developed by Walter Bruch, an engineer at the German company Telefunken, and presented as a standard television broadcasting 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 component of the color in the average television picture and to avoid redundant coding, R-Y difference and B-Y (Y is the overall brightness of the monochrome TV signal). The PAL system uses the YUV color model.

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

In this case, each color difference signal is repeated in next line with the 15.625 kHz frequency rotated 180 degrees, making the PAL decoder completely eliminate phase errors (typical of the NTSC system). To eliminate the phase error, the decoder adds 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 monochrome image.

Subjectively, due to the greater sensitivity of the eye to the brightness component, such deterioration is almost not noticeable in average pictures. Application digital processing signal further smoothes out this drawback.

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 ones are used as the missing lines R-Y signal or B-Y, 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.

Chroma signal in the SECAM standard, it is transmitted in frequency modulation (FM), one color component in one television line, alternately. The previous signal is used as the missing lines R-Y or B-Y accordingly, receiving it from memory. So, when the transmitter transmits only the signal R-Y, serving to influence the red phosphors of one row, the memory drives the blue phosphors, transmitting to them the same color changes that were in the previous row when the signal was received B-Y. The storage duration is equal to the transmission time of one line. Consequently, in television with a 625-line decomposition, the storage duration is 64 μs.

In analog television receivers, memory is used to implement delay line. During the return stroke of the beam, after each line, double commutation is performed to direct incoming signal to the corresponding electron gun, and the signal coming out of the delay line is directed to the electron gun, which directly received the direct signal during transmission previous line. Since creating a delay line through which an electrical signal would pass is difficult due to the too long period of time - 64 μs, ultrasound is used instead of electrical signals. Signals with a frequency varying from zero to 1.5 MHz generate corresponding mechanical oscillations at the input of the delay line, which take 64 μs to pass through. They are then converted back into electrical signals. The first delay lines were a rod made of solid material, at the ends of which there were piezoelectric elements. The next generation of delay lines was made in the form of a rectangular plate, and piezoelectric elements were located at the corners. This made it possible to reduce the dimensions due to repeated reflection of vibrations from the edges of the rectangle. Electromechanical transformation is based on the phenomenon of piezoelectricity (the occurrence of vibrations in certain crystals such as quartz or titanate when changing electrical voltages and vice versa, the occurrence of electrical voltages during vibration of such crystals). That. in the delay line, a piezoelectric crystal is attached to each end of the steel rod. A crystal installed at the input converts electrical signals into mechanical vibrations. These oscillations propagate along the rod and after 64 μs reach the second piezoelectric crystal, where they generate electrical signals of the same shape as those applied to the input. Modern technology uses digital signal processing, which involves delaying the signal by storing random access memory signal processor.

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.

The use of frequency modulation, alternating color signal transmission and the YDbDr color model is distinctive feature SECAM from other analog television standards. The fact that in SECAM, unlike PAL and NTSC systems, color signals are transmitted alternately, modulating the subcarrier in frequency, makes it possible to save color background images without changes due to phase or amplitude distortions.

According to comprehensive studies conducted in 1965–66 at OSCT-2 ( Experimental color television station) of both systems, when choosing the best one for its widespread implementation in the USSR, neither of the two systems showed decisive technical or economic advantages over the other. The advantage of the SECAM system was less sensitivity to distortion during transmission over long-distance lines and during video recording; The disadvantage is the complexity of the equipment when mixing signals.

SECAM versions

Several modifications of the SECAM standard are used around the world. The method of transmitting color difference signals is the same in all cases, including the so-called pre-emphasis, and they differ only in the method of encoding the monochrome video signal, audio encoding and spectrum width. In fact, the method of identifying color could also be different - since only one signal is transmitted in each line, the decoder must correctly determine which one. For this, a method similar to “flashes” in PAL and NTSC systems could be used - in the invisible part of the line, at the end of the blanking pulse, an unmodulated subcarrier was transmitted, in the case of SECAM, either 4.406 MHz or 4.25 MHz, based on the frequency value, and identification occurred. Another method is the transmission of specially modulated signals at the end of the vertical blanking pulse, where the subcarriers took the extreme possible values ​​across the line, which simplified identification, especially in conditions of interference. Currently, this method is either not used or is a backup method, for example, in Russia both signals are transmitted simultaneously, and in France only the first option. But initially the second option was the main one, and once upon a time in the USSR and the countries of northern Africa only it was used.

Currently broadcast television channels in Russia is broadcast in the SÉCAM system, however, in cable broadcasting networks the vast majority of analogue television channels, including those presented on the air, are transmitted in the PAL system, which makes it impossible to watch them on old Soviet TVs in color.

Backronyms

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

Notes

Television broadcast standards
Analog
SECAM PAL NTSC
Multichannel audio BTSC (MTS) NICAM Zweiton (A2, IGR)
Additional signals Teletext Subtitles CGMS-A GCR PDC VBI VEIL VITC WSS XDS
Digital
HDTV DVB ATSC ISDB SBTVD
Multichannel audio AAC (5.1) MP2 (Musicam) PCM LPCM
Hidden signals Teletext Subtitles CPCM AFD EPG






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