Color difference signal


In order to transmit a color tone and color saturation containing the color image, the brightness signal is subtracted from three primary color signals, Three chromaticity signals that only contain chromaticity information, we call them as a color difference signal.

Use a primary color signal to subtract the brightness signal to obtain a color difference signal. For example, a blue difference signal (B-Y), red difference (R-Y) two color difference signals and a luminance signal (Y). Strictly speaking, there are three color difference signals, namely R-Y, B-Y, G-Y. But only two are independent, and the third can use two other two.

Color difference signal

Transfer and terminal

Due to the color of any frequency, the green component has the greatest contribution to the brightness, and the value of Gy is the smallest, obviously, in the signal transmission process, transmits one Small signals are unfavorable to improve signal-to-noise ratio, so the two color difference signals, and luminance signals, and luminance signals, and luminance signals, and luminance signals are selected as the transmission signal.

has a color difference signal output in Xbox, PS2, PS3, and DVD. There are two plugs in the home TV. There are two plugs, a plug represents a blue difference signal, a plug, represents a red difference signal. The color difference signal can be converted to RGB, YUV, VIDEO, and other signals.


During color TV signal transmission, the color difference signal is transmitted. So why do you want to transfer a color difference signal without transferring a primary color signal? We know that the size of the three-primary color signal determines the brightness of the color, and the proportional relationship between the three-base color determines the color of color, so the three-base color signal contains both color brightness. The information also contains colored chromaticity information. According to the compatible conditions, a brightness signal must be transmitted, and all brightness information of the color image is included in the brightness signal. If the primary color signal is then transmitted, the luminance signal is transmitted twice, which causes interference during signal transmission, so general The color difference signal is transmitted without transmitting the primary color signal.


Compatible Effects

When elected, Y, Ry, by the three signals, Y only represents the brightness of the transmitted scene, not color Spend. Moreover, when the transmitted image is black and white, the color difference signal is zero because any black and white picture has only a hierarchical change in brightness, so their tricho signal is always equal. The color difference signal only indicates that the chromaticity does not represent brightness, and the contribution of the three-color difference signal is zero. Therefore, the distortion of the color difference signal does not affect the brightness. Therefore, only the black and white TV only receives the Y signal in the color TV station, and its effect is the same as the show that watchs the black and white TV station.

Enables constant brightness principle

so-called constant brightness principle, refers to the brightness of the subject in the transmission system, which is constant, ie, is distortion with the color difference signal. No correlation, only related to the size of the brightness signal itself.

facilitates high frequency mixing

Since the transfer brightness signal occupies all of the video bandwidth 0-6MHz, the transfer chromaticity signal only uses a narrower band 0-1.3 MHz. Therefore, the three primary color signals restored by the television receiver include only lower frequency components, and the reaction is in the screen, only the color contour of the large area; the image color details, that is, the high frequency component is from the brightness signal. add. That is to say, a high-definition black and white image is displayed by the brightness, and then the chroma signal is low-definition coloring on this black and white image.

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