Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media.Video systems vary greatly in the resolution of the display, how they are refreshed, and the rate of refreshed, and 3D video systems exist. They can also be carried on a variety of media, including radio broadcast, tapes, DVDs, computer files etc.Video technology was first developed for mechanical television systems, which were quickly replaced by cathode ray tube (CRT) television systems, but several new technologies for video display devices have since been invented. Charles Ginsburg led an Ampex research team developing one of the first practical video tape recorder (VTR). In 1951 the first video tape recorder captured live images from television cameras by converting the camera's electrical impulses and saving the information onto magnetic video tape.The use of digital techniques in video created digital video, which allowed higher quality and, eventually, much lower cost than earlier analog technology. After the invention of the DVD in 1997 and Blu-ray Disc in 2006, sales of videotape and recording equipment plummeted. Advances in computer technology allowed even inexpensive personal computers to capture, store, edit and transmit digital video, further reducing the cost of video production, allowing program-makers and broadcasters to move to tapeless production. The advent of digital broadcasting and the subsequent digital television transition is in the process of relegating analog video to the status of a legacy technology in most parts of the world. As of 2015, with the increasing use of high-resolution video cameras with improved dynamic range and color gamuts, and high-dynamic-range digital intermediate data formats with improved color depth, modern digital video technology is slowly converging with digital film technology.
Video can be interlaced or progressive. Interlacing was invented as a way to reduce flicker in early mechanical and CRT video displays without increasing the number of complete frames per second, which would have sacrificed image detail to remain within the limitations of a narrow bandwidth. The horizontal scan lines of each complete frame are treated as if numbered consecutively, and captured as two fields: an odd field (upper field) consisting of the odd-numbered lines and an even field (lower field) consisting of the even-numbered lines.Analog display devices reproduce each frame in the same way, effectively doubling the frame rate as far as perceptible overall flicker is concerned. When the image capture device acquires the fields one at a time, rather than dividing up a complete frame after it is captured, the frame rate for motion is effectively doubled as well, resulting in smoother, more lifelike reproduction (although with halved detail) of rapidly moving parts of the image when viewed on an interlaced CRT display, but the display of such a signal on a progressive scan device is problematic.In progressive scan systems, each refresh period updates all scan lines in each frame in sequence. When displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary and moving parts of the image. When displaying a natively interlaced signal, however, overall spatial resolution is degraded by simple line doubling—artifacts such as flickering or "comb" effects in moving parts of the image appear unless special signal processing eliminates them. A procedure known as deinterlacing can optimize the display of an interlaced video signal from an analog, DVD or satellite source on a progressive scan device such as an LCD Television, digital video projector or plasma panel. Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material.Video can be transmitted or transported in a variety of ways. Wireless broadcast as an analog or digital signal. Coaxial cable in a closed circuit system can be sent as analog interlaced 1 volt peak to peak with a maximum horizontal line resolution up to 480. Broadcast or studio cameras use a single or dual coaxial cable system using a progressive scan format known as SDI serial digital interface and HD-SDI for High Definition video. The distances of transmission are somewhat limited depending on the manufacturer the format may be proprietary. SDI has a negligible lag and is uncompressed. There are initiatives to use the SDI standards in closed circuit surveillance systems, for Higher Definition images, over longer distances on coax or twisted pair cable. Due to the nature of the higher bandwidth needed, the distance the signal can be effectively sent is a half to a third of what the older interlaced analog systems supported.
Video can be interlaced or progressive. Interlacing was invented as a way to reduce flicker in early mechanical and CRT video displays without increasing the number of complete frames per second, which would have sacrificed image detail to remain within the limitations of a narrow bandwidth. The horizontal scan lines of each complete frame are treated as if numbered consecutively, and captured as two fields: an odd field (upper field) consisting of the odd-numbered lines and an even field (lower field) consisting of the even-numbered lines.Analog display devices reproduce each frame in the same way, effectively doubling the frame rate as far as perceptible overall flicker is concerned. When the image capture device acquires the fields one at a time, rather than dividing up a complete frame after it is captured, the frame rate for motion is effectively doubled as well, resulting in smoother, more lifelike reproduction (although with halved detail) of rapidly moving parts of the image when viewed on an interlaced CRT display, but the display of such a signal on a progressive scan device is problematic.In progressive scan systems, each refresh period updates all scan lines in each frame in sequence. When displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary and moving parts of the image. When displaying a natively interlaced signal, however, overall spatial resolution is degraded by simple line doubling—artifacts such as flickering or "comb" effects in moving parts of the image appear unless special signal processing eliminates them. A procedure known as deinterlacing can optimize the display of an interlaced video signal from an analog, DVD or satellite source on a progressive scan device such as an LCD Television, digital video projector or plasma panel. Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material.Video can be transmitted or transported in a variety of ways. Wireless broadcast as an analog or digital signal. Coaxial cable in a closed circuit system can be sent as analog interlaced 1 volt peak to peak with a maximum horizontal line resolution up to 480. Broadcast or studio cameras use a single or dual coaxial cable system using a progressive scan format known as SDI serial digital interface and HD-SDI for High Definition video. The distances of transmission are somewhat limited depending on the manufacturer the format may be proprietary. SDI has a negligible lag and is uncompressed. There are initiatives to use the SDI standards in closed circuit surveillance systems, for Higher Definition images, over longer distances on coax or twisted pair cable. Due to the nature of the higher bandwidth needed, the distance the signal can be effectively sent is a half to a third of what the older interlaced analog systems supported.
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