PAL, SECAM and NTSC is a system in which there is a stream signal (antenna, cable, satellite receiver, or DVD). The most important thing to know about them and a bit of history in our article
About what FELL or SECAM most of us learned only in late 80-ies, when brought from abroad or bought in retail stores the first imported video recorders, video players and video cassettes with movies or music. Imagine the disappointment when it turned out that they are not so easy to connect to our, Soviet TV, and plugging in, it appeared that the picture was in black and white then, turning to the master, the owner of "Vedic" learned that his TV only accepts color system "SECAM", and all the bought video cassettes recorded in the "PAL" or, even worse, in one of the standardsNTSC"
In simple terms, PAL, SECAM and NTSC is a system "chrominance" or color. When they mismatch (at the signal source and the TV) the picture on the screen will be black and white (and can be narrowed or even strips instead of pictures). The signal itself, which handles the television contains information about the brightness (black-and-white picture) and chromaticity (about how b/W picture should be colored). So, information about the color "paint" is encoded in one of the systems PAL, SECAM...
How do You remember the story about color TV to obtain a color image, just three colors: red, blue and green. Therefore, the TV signal should contain information about these three colors and the signal "brightness"
I won't bore You with technical details, but let's just say: it turned out that, knowing the information about the brightness (Y) and signal blue (In) color and red (R), it is possible, by simple calculations (equations) to find information about green color (G).
For example, if the given "point" (pixel) of the image (taking it as 100%) must consist of a 50% red, 30% and 20% blue, with only blue and red can be calculated: 100 - (50 + 20) = 30% green must be in this "point"
It remains only to decide exactly how to transmit this information (about the color) and "teach" circuit TV to process this info, thus was born the system of transmission and processing of color images:
The TV color system of NTSC were developed at 1953 year in United States National television standards Committee (National Television Standards Committee). NTSC was adopted as the standard system color television in Canada, Japan and several countries of the American continent. As signals for the transmission of color information in the system of NTSC adopted color-difference signals (R-Y and B-Y). Transmission of these signals was carried out in the spectrum of the luminance signal on one color subcarrier frequency, with the phase shift in the 90 degrees
There are several standards for NTSC, the most popular are: NTSC 4.43 and NTSC 3.58. They all have frequency shifts fields 60Hz (more precisely: 59,94005994 Hz) number of lines: 525 (486 active), and the numbers: 4.43 or 3.58 is the frequency at which transmitted the color information (frequency modulation)
The main disadvantage of the system is the possibility of distortion in the transmission of color. They cause change in the color tone on the TV screen depending on the brightness of the image area. For example, human faces on the screen are painted in a reddish color in the shadows and greenish - lit areas. To reduce these distortions, a TV NTSC are equipped with regulators color tones: TINT CONTROL. This control allows for a more natural painting with a single brightness, but distortion of the color tone brighter or darker areas of the image however, even increase
PAL (eng. Phase-alternating by line phase alternating line) analog color television system developed by the engineer of the German companyTelefunken" Walter Bruch and presented as a broadcast standard in 1967 year. System PAL is the main system of color television in Europe (except France and, until recently, Russia, Ukraine and Belarus), Asia, Australia and several countries in Africa and South America
Main features: frequency of change of fields 50Hz number of rows 625 (576 active), the modulation frequency of the color subcarrier (color information) 4.43 MHz
As the number of full frames in the PAL is 25 per second - it was close to 24-m standard frame filming, so the migration process inoplanetnyh movies TV standard PAL was easy and convenient (no need to complicate the non-existent extra frames like NTSC)
PAL phase of one subcarrier chrominance video signals from line to line is changed to 180 degrees. In addition, the receiver uses a delay line on one line (64 ISS). That is, when interlaced scanning, there are two chrominance signals with a relative delay of one line. The phase variation from line to line by 180° causes phase error of equal magnitude have different signs ("+" and "-"). The addition of the voltage at the input of the delay line with an inverted voltage on its output fixes a bug (crash) phase, and the colors on the TV screen looks more natural than when watching broadcasts encoded NTSC
A variation of the standard PAL-60, maintains the frequency changer 60 Hz fields adopted in the NTSC system, whereby you could "work" on equipment and TVs that have this frequency vertical scan
In 1958, French engineer Henri de France invented a new system called SECAM (SEquential Couleur Avec Memoire), which was absent the main disadvantage of NTSC — distortion of the colour tone. As between the USSR and the USA at the time was the cold war, there is nothing strange that SECAM and not NTSC was adopted by the Soviet Union as the main systems of color television, SECAM is called: the Soviet-French standard
In 1966 political "feature" SECAM came out, when the Soviet government used the agreement with France based on distribution on the territory of the USSR only SECAM system) as an excuse to ban American broadcasting Corporation NBC record on videotape of demonstrations in Moscow. At the last minute, the Soviet government demanded an end to NTSC recording, explaining that otherwise violate the agreement
Key features SECAM: 625 lines with a frequency 25 frames per second (the same as in PAL), the main difference is the method of transmitting signals "red" and "blue". Was used frequency modulation (FM) signal, each color is transferred to their frequency (4,25 and 4,40625 MHz)
Color-difference signals in SECAM are transmitted alternately: for one line — signal R – Y for the next Y, etc. Colour information as for R – Y and V – Y is removed through the line and the "remembered" special delay circuit by one line (64 µs), in order to be able to add them up and allocate the signal "green"
Thus it turns out that each frame contains two times less information about the "color" than when the signal processing of PAL, hence some blurring of the color painting fine details, but (and this was important at the time) the signal in the SECAM was more noise immune. A picture might ruffle a bad antenna or signal, but there were a color
MESECAM (Middle East SECAM - SECAM Middle East) is a type of SECAM and is used to ensure that the VCR is operating in the PAL standard had the ability to record programs broadcast in the SECAM system. It was not the best, but quite simple and inexpensive to develop, the need for which appeared with the massive spread of Vidic in the countries of Eastern Europe (USSR) and Asia, which received a TV signal in the SECAM system
The quality of the image, which provided the above system, over time, ceased to hold as producers of TV equipment of viewers. The apparatus was improved, the display grew and 625 lines is not enough to transmit high quality and clear images, thus was born the HDTV - high-definition television (HDTV)
The human eye is able to see the image with a radius of nearly 180 degrees from the horizontal without rotation of the head, but the vertical is much smaller, the nose is hampered, then the forehead... ), so as the main format was adopted the format of the signal 16x9, instead of 4x3 (for more information about formats read here: formats the TV screen and signal), and the number of rows was increased to 1080
In addition, the high-definition television for transmitting images and sound are used exclusively digital technology based on the stream compression video and audio data, and to distribute high definition media created two new formats: HD DVD and Blu-Ray