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.
This represents a difference of 49 lines at 50 Hz and 45 lines for 60 Hz. Those lost lines are necessary, they represent the time required for the electron beam scanning the CRT can be traced from the bottom of an image to the top. This technical problem does not exist with LCD panels and plasma panels, but retained for compatibility.
This problem is partially solved by means of a birefringent crystal blades that spread out the details by splitting light rays. This results in a loss of definition, which gives the PAL and SECAM systems vertical resolution multiplied by 0.7 (Kell factor), which is not actually that of approximately 400 lines. When the display is not interlaced, the term progressive applies.
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.
Analog video standard across the world include NTSC, PAL and SECAM. PAL or SECAM standards have no relationship with the scan of an image, these standards only allow you to add color to black and white images. In the early days of television, only the luminance defines the image by a number of horizontal dots and also by three factors shade of gray.
When color television was first introduced it took b/w TVs to render an image, the luminance signal has been preserved and added a signal that the black and white TV would not know and therefore not appear even as a parasite signal with backward compatibility. So two color differences R'-Y and B'-Y (the 'means were added so that signals underwent own correction to a gamma curve to overcome, at the time, a problem of non-linearity restitution CRTs). By combining with luminance, it is possible to extract green.
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.
This represents a difference of 49 lines at 50 Hz and 45 lines for 60 Hz. Those lost lines are necessary, they represent the time required for the electron beam scanning the CRT can be traced from the bottom of an image to the top. This technical problem does not exist with LCD panels and plasma panels, but retained for compatibility.
This problem is partially solved by means of a birefringent crystal blades that spread out the details by splitting light rays. This results in a loss of definition, which gives the PAL and SECAM systems vertical resolution multiplied by 0.7 (Kell factor), which is not actually that of approximately 400 lines. When the display is not interlaced, the term progressive applies.
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.
Analog video standard across the world include NTSC, PAL and SECAM. PAL or SECAM standards have no relationship with the scan of an image, these standards only allow you to add color to black and white images. In the early days of television, only the luminance defines the image by a number of horizontal dots and also by three factors shade of gray.
When color television was first introduced it took b/w TVs to render an image, the luminance signal has been preserved and added a signal that the black and white TV would not know and therefore not appear even as a parasite signal with backward compatibility. So two color differences R'-Y and B'-Y (the 'means were added so that signals underwent own correction to a gamma curve to overcome, at the time, a problem of non-linearity restitution CRTs). By combining with luminance, it is possible to extract green.
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