Color TVColour television system, mainly refers toColor TV signalEncoding and decoding methods.After the color image is photographed, three primary color signals ER, EG and EB are generated, which respectively reflect the red, green and blue primary color component information of the original image.At the transmitting end, the process of composing the three signals (including all chrominance and brightness information of the transmitted image) into a color full TV signal is called encoding.At the receiving end, the process of restoring the three primary colors of the image from the color full TV signal is called decoding.According to different purposes of use, color TV systems can be divided into compatible and incompatible systems. All color TV broadcasts in the world use compatible systems.[1]
Color TV pairTricolorThe brightness andChromatic aberration signalThe processing method of.Different processing methods of three primary color signals in color TV system constitute different color TV systems.The broadcast color TV system is required to be compatible with black and white TV.For this reason, color TV is based on the principle that a certain proportion of the three primary colors in the additive color mixing method can be mixed into various colored lights, including white light. At the same time, in order to be compatible with and compress the transmission band, red (R), green (G), blue (B) three primary color signals are generally composed of brightness signal (Y ') and blue and red two color difference signals (B-Y)', (R-Y) ',The brightness signal can be used to transmit black and white images, and the combination of color difference signal and brightness signal can restore the red, green and blue primary color signals.Therefore, compatible color TV transmits chrominance signals within the same video frequency band in addition to the luminance signal and accompanying sound signal that are the same as those of black and white TV.Chromaticity signal is the same twoChromatic aberration signalIt is formed by modulating the color subcarrier at the high frequency end of the video frequency band.In order to prevent modulation overload of color difference signal, compress (B-Y) ', (R-Y)', and use U, V to represent them.There are three main color TV systems in the world.NTSC systemIt is a color TV system adopted by the United States, Japan and other countries, characterized by simple decoding circuit and low cost.PAL system is a system developed by the Federal Republic of Germany in 1963 to reduce the phase sensitivity of NTSC system. It was officially broadcast in 1967, and China adopted this color TV system.It is insensitive to phase deviation and is subject tomultipathThe influence of ghost color caused by reception is small.SECAM system is also a color TV system developed to improve the phase sensitivity of NTSC system, which is adopted by France, Russia and other countries.
Its characteristic is that it is less affected by multi-path reception in transmission.
National differences
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Major countries and regions with three color TV systems: current status of color TV systems
NTSC system: Used in Mexico, Japan, Taiwan, Canada and other countries and regions;
PAL system: Germany, China, Hong Kong, the United Kingdom, Italy, the Netherlands, the Middle East and other countries and regions;
SECAM system: used by the former Soviet Union, Eastern Europe and African countries.
Classification Introduction
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Introduction to classification
Strictly speaking, there are many types of color TV sets. For example, there are often 21 types of color TV sets on international lines. However, it is of no practical significance to study and discuss color TV sets in detail.In people's general impression, there are only three types of color TV, namely, NTSC, PAL, SECAM and other three types of color TV.
1. Orthogonal balanceamplitude modulationNational Television Systems CommitteeNTSC system。The main countries adopting this system are the United States, Canada and Japan.
2. Phase AlternativeLine, or PAL system for short, is a line by line phase inversion system of orthogonal balanced amplitude modulation.China, Germany, Britain and othersNorthwest EuropeThe state adopts this system.
3. Row rotationfrequency modulationSequential ColeurAvecMemoire (SECAM for short).This system is adopted by France, the former Soviet Union and some countries in Eastern Europe.
Advantages and disadvantages
NTSC (National Television System Committee) system is generally calledQuadrature modulationFormula (for two colorsSubcarrierSignalingQuadrature amplitude modulation）Color TV system;PAL (Phase Alternating Line Phase Inversion) system is generally called line by line phase inversion (for two color subcarrier signals, the phase inversion is in turn, but the modulation mode is still quadrature amplitude modulation) color TV system;SECAM (SystemeElectroniquePourCouleurAvecMemoire) is generally calledTransport in turnFormula (for two color subcarriersModulated signalThe color signal is transmitted in turnfrequency modulationModulation transmission) color TV system.
NTSC systemThe advantage is that the TV receiver circuit is simple, and the disadvantage is that it is easy to produce color bias. Therefore, NTSC TV sets have a manual color control circuit for users to choose;PAL system and SECAM system can overcome the disadvantage that NTSC system is easy to color cast, but the circuit of TV receiver is complex, which requires one more line of delay line circuit than NTSC system, and the image is easy to produce color flicker.Therefore, each of the three color TV systems has its advantages and disadvantages, and no one can defeat each other by comparing the results. Therefore, the three color TV systems have coexisted with each other for more than 50 years.The following is the use of
M：4.5MHz，Adopted by the United States, Japan, Canada and other countries.
Other types
However, with the increase of program sources, such as satellite TV, laser discs and various video tapes, there are multi standard TV sets andRear projection, such as 2, 4, 11, 17, 21, 28, etc.The system mentioned here is neither PAL, NTSC nor SECAMColor TVThe three systems are not black and white TV systems, but how many ways TV sets receive.For example, system 2 means that it can receive TV images and accompanying sound from both mainland China and Hong Kong;28 system can receive 6 kinds of TV broadcasts, 8 kinds of special video recorders, 7 kinds of laser video discs and 7 kinds of videoCable TV system。
colour television system
There are 13 television systems in the world, three major onesColor TVStandard, compatible and combined into more than 30 differentTV system。However, according to the survey of more than 200 countries and regions in the world, only 17 of them are used: 8 PALs, 2 NTSCs and 7 SECAMs.PAL/B and G are the most widely used in 60 countries and regions;NTSC/M，Used by 54 countries and regions;SECAM/K1，It is used in 23 countries and regions.So the multi system TV is not full system, but as long as it can receive PAL/DK、B、G、I，NTSC/M，SECAM/K、k1、B、G、The system can receive TV programs from more than 80% of countries and regions in the world.
In addition, multi systemRear projectionIt can also receive programs played by laser discs and multi standard video tapes, making it very convenient to use one machine for multiple purposes.In order to realize multi-mode reception of rear projection, many new circuits should be set in the rear projection.Multi system rear projectiondecodeIt is also different from ordinary rear projection because of the three coding methods of color TVSubcarrierThe frequencies are different, so three types of recognition and conversion circuits should be set before decoding.General basisField frequencyDifferent firstNTSC systemSeparated from PAL and SECAM system, and then according to SECAM systemfrequency modulationLine rotation system and PAL system are used to identify SECAM system and PAL system.These system identification work is carried out in the integrated circuit. Generally, the rear projection will automatically identify. Of course, you can manually force it to execute a certain system.
For color TV, in addition to the above characteristicsTricolorDifferent signal processing methods are divided into many color TV systems.According to different purposes of use, color TV can be divided into compatible and incompatible systems.The so-called "compatible" means that "color TV and black and white TV can watch each other".That is, color TV programs can beBlack and white TVReceive and display as black and white image;Black and white TV programs can also be received by color TV sets and displayed as black and white images.The former is usually called compatibility, and the latter is called reverse compatibility.The world's broadcast color TV adopts compatible system, while non compatible color TV is mainly used forApplied TV。
Color TV can be divided into:
(1) Simultaneity ColorTelevision;
(2) Sequential ColorTelevision;
(3) Sequence - simultaneous system.
In the sequence system, the red, green and blue primary color image signals that the camera travels to are transmitted to theKinescope, using the human eyeVisual persistenceProperties willTricolorImage BlendingColor imageThe sequence system can be divided into field sequence system, line sequence system and point sequence system. They are field by field, line by line and point by point sequential transmission of three primary color signals.The advantages of sequential system are simple equipment, good color image quality, but poor compatibility or incompatibility.In order to overcome the disadvantages of the sequential system, the simultaneous system appears. It encodes the R, G, and B primary colors into brightness signals and chroma signals for simultaneous transmission. After decoding, the three primary color signals R, G, and B are obtained, and then color images are synthesized by the picture tube. The advantage of the simultaneous system is that it is compatible,imageThe quality is good, but the equipment is complex, and the luminance and chrominance signals often interfere with each other.
Sequence simultaneous system is a combination of the above two systems.For example, one primary color signal can be transmitted frequently, while the other two primary color signals can be transmitted sequentially, and thenKinescopeThe advantages and disadvantages of the synthetic color image in are the same as those of the simultaneous system. When developing, the three systems all use the principle of spatial color mixing, and the sequential system also uses the principle of temporal color mixing.Obviously, compatible color radio and television can only adopt simultaneous system or sequential simultaneous system, and sequential system is generally used in color application television.
Features
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NTSC
Standard of three color TV sets
It was created by the United States in 1952National Television Standards CommitteeSpecified color TV broadcasting standard, which adopts orthogonal balanceamplitude modulationTherefore, it is also called orthogonal balanced amplitude modulation system.Most of the United States, Canada, etcwestern hemisphereThis system is adopted by China, Taiwan, Japan, South Korea and the Philippines.
PAL system
It is the color television broadcasting standard designated by West Germany in 1962. It adopts line by line phase inversion orthogonal balanceamplitude modulationIt overcomes the disadvantage of NTSC phase sensitivity resulting in color distortion.Some Western European countries, such as West Germany and Britain, Singapore, mainland China and Hong Kong, Australia and New Zealand, adopt this system.PAL systemAccording to different parameter details, it can be further divided into G, I, D and other systems, of which PAL-D system is the system adopted in mainland China.
SECAM system
SECAM is the abbreviation of French, which means the color signal system of sequential transmission and storage recovery. It is a new color TV system proposed by France in 1956 and formulated in 1966.It also overcameNTSC systemPhase distortionHas disadvantages, but usesTime separation methodTo send twoChromatic aberration signal。Countries using SECAM system are mainly concentrated in France, Eastern Europe and the Middle East.In order to receive and process TV signals of different systems, TV receivers and video recorders of different systems have also been developed.
Main problems
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The televisions sold in the market are really dazzling. People can not only buy imported advanced new televisions with full or multiple systems, but also domestic televisions have reached the world's advanced level, which are popular with consumers.In terms of viewing programs, you can not only watch multiple programs broadcast by domestic TV stations, but also enjoy foreign TV video programs, imported VCD TV programs and satellite TV programs.However, some problems often occur when a TV set in good condition is used for normal viewing.If some can't receive color, some can't receive sound, and some can't even receive programs, the reason is often becauseTV systemincorrect.
Characteristics of International Television System
The standard of AC power supply in the world is not uniform. Therefore, if TV sets of different systems are used interchangeably, there will be various problems, even no reception, and they must be transformed. However, this transformation sometimes pays more than the cost. Television broadcasting and television production in every country follow an established system (black and whiteTV systemAnd color TVCoding systemDifferent technical content, combined into their own country's specific television system), so that there are about 10 kinds of black and white TV systems and 3 kinds of color TVColour codingThe combination of systems forms about 39 types of TV system combinations. China adopts PAL/D and K systems.There are various kinds of propaganda about the new TV format: 28 format, 21 format, multi format, full format and so on, but technically, it refers to the ability of the TV to receive a variety of TV program formats.
When you want to enjoy imported video programs, VCD programs and satellite TV programs, these programs themselves bear the brand of the production country's system, and are different from China's PAL/DK in terms of technical standards of television broadcasting. Therefore, if you want to watch them normally, you need to try to make the TV and the TV programs you want to watch have the same system. There are usually two methods:
One is to change the format of TV programs into the same format as the TV set used;
The second is to enable the TV set to have the reception ability of multiple systems.
For the former, if you want to achieve full conversion success and achieve satisfactory results, you can use digital converters, but at least thousands of yuan should be invested;If a simple part of the analog brake is used, although it is about one hundred yuan, it is not necessarily ideal to go down, and only the selection has the correspondingTV systemA TV set with reception capacity can save money without adding another oneChassisThe effect is good and beautiful.So the new style appears in the price of the storeColor TVOne of the distinctive features of the system is that there are many systems, some called 28 system, some called 21 system, some vaguely called multi system, and some even called full system.Of course, if you can afford it, you should be prepared to buy all the TV sets in the world, but it is often too wasteful.The realistic scheme is to choose according to the type of TV program system that may be received.
