Video brings together all the techniques for recording and restitution of moving images with or without sound, in an electronic medium and not of photochemical kind. The TV picture is a series of line scans, from the top, and ending at the bottom of the screen. In the early days of television, the quality of phosphorescent tube elements was poor. Thus, online videos and games beam sweeping the bottom of a screen, the top disappears, resulting in a flickering, strongly felt by the human eye at 25 Hz or 30 Hz.
The easiest solution would have been accelerating the scan rate, but this also required to increase the frame rate, which was expensive. A more clever solution was to miss a row in each image, thus doubling the scan rate while keeping the same bandwidth. Thus, a first pass displays all the odd lines in half the time for a whole image and a second pass shows missing line pairs: this is called interlacing. We obtain the same number of scan lines to an image, and twice flushed the screen to display a single image.
Due to the capture of two frames each second of 1:50, the time of exposure in video (25i). The first cameras operating on the same principle as televisions analyzed the image formed by the lens with a CRT. Since the late 1980s, they have a photo sensor CCD or CMOS type. There are different formats of video images, which depend mainly on frequency of vertical sweep of images. It can be seen that there is a difference between the number of lines composing the frame and the number of lines displayed.
How now add to Y color information to regain our original RGB? Since there was already light (Y), it was necessary to color the black/ white with color information, they had no light value, but only indications of hue and saturation. Once the b/w was colorized, they had to find the trick that would transmit light (Y) and chroma (C).
Free lines are partially taken advantage of: they place the signals teletext, subtitling and also the time-code of professional video equipment. There are two scanning frequencies of the image: The vertical scanning, which takes place from top to bottom is used to compose the image. It is done 50 or 60 times per second.
These solutions were found and implemented. Thus were developed in the United States (NTSC0, SECAM in France and PAL in Germany. Coding transforms RGB black/white color-compatible signal. NTSC, PAL and SECAM are three types of mutually incompatible encodings. Transformation from one type of encoding to another is called transcoding. None of the three solutions is nevertheless transparent, far from it. A transcoded signal suffers from more or less visible defects depending on the coding artifacts.
An encoded signal of the kind is stated in a composite video signal, because it contains several different types of sources. Video standards use the composite range from U-MATIC / U-MATIC SP HSV through the 8mm or Video 8, Betamax, the VCR or the V2000. In view of damage caused by coding, it became urgent to absolve production. In the early 1980s, Sony devised a video format with separate components consisting of several distinct signals conveyed by separate cables: Betacam / Betacam SP.
To remain compatible with black and white, the company carefully avoided RGB, and naturally selects a format containing the Y, plus information conveyed by two chrominance signals U and V (also known as Cr and Cb). These components are connected by formulas U = R - Y and V = B - Y, where Y = + 0,30R 0,59V 0,11B + (the coefficients being different according to the coding used). This transformation from RGB to YUV is called mastering. Metal stamping is a simpler coding operation that generates no degradation, while offering the advantage of compatibility Y.
The easiest solution would have been accelerating the scan rate, but this also required to increase the frame rate, which was expensive. A more clever solution was to miss a row in each image, thus doubling the scan rate while keeping the same bandwidth. Thus, a first pass displays all the odd lines in half the time for a whole image and a second pass shows missing line pairs: this is called interlacing. We obtain the same number of scan lines to an image, and twice flushed the screen to display a single image.
Due to the capture of two frames each second of 1:50, the time of exposure in video (25i). The first cameras operating on the same principle as televisions analyzed the image formed by the lens with a CRT. Since the late 1980s, they have a photo sensor CCD or CMOS type. There are different formats of video images, which depend mainly on frequency of vertical sweep of images. It can be seen that there is a difference between the number of lines composing the frame and the number of lines displayed.
How now add to Y color information to regain our original RGB? Since there was already light (Y), it was necessary to color the black/ white with color information, they had no light value, but only indications of hue and saturation. Once the b/w was colorized, they had to find the trick that would transmit light (Y) and chroma (C).
Free lines are partially taken advantage of: they place the signals teletext, subtitling and also the time-code of professional video equipment. There are two scanning frequencies of the image: The vertical scanning, which takes place from top to bottom is used to compose the image. It is done 50 or 60 times per second.
These solutions were found and implemented. Thus were developed in the United States (NTSC0, SECAM in France and PAL in Germany. Coding transforms RGB black/white color-compatible signal. NTSC, PAL and SECAM are three types of mutually incompatible encodings. Transformation from one type of encoding to another is called transcoding. None of the three solutions is nevertheless transparent, far from it. A transcoded signal suffers from more or less visible defects depending on the coding artifacts.
An encoded signal of the kind is stated in a composite video signal, because it contains several different types of sources. Video standards use the composite range from U-MATIC / U-MATIC SP HSV through the 8mm or Video 8, Betamax, the VCR or the V2000. In view of damage caused by coding, it became urgent to absolve production. In the early 1980s, Sony devised a video format with separate components consisting of several distinct signals conveyed by separate cables: Betacam / Betacam SP.
To remain compatible with black and white, the company carefully avoided RGB, and naturally selects a format containing the Y, plus information conveyed by two chrominance signals U and V (also known as Cr and Cb). These components are connected by formulas U = R - Y and V = B - Y, where Y = + 0,30R 0,59V 0,11B + (the coefficients being different according to the coding used). This transformation from RGB to YUV is called mastering. Metal stamping is a simpler coding operation that generates no degradation, while offering the advantage of compatibility Y.
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