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Video
Video is an electronic medium for the recording, copying, playback, broadcast, and display of moving-image media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) systems, which, in turn, were replaced by flat-panel displays.
Video systems vary in display resolution, aspect ratio, refresh rate, color reproduction, and other qualities. Both analog and digital video can be carried on a variety of media, including radio, magnetic tape, optical discs, computer files, and network streaming.
The word video comes from the Latin video, "I see," the first-person singular present indicative of videre, "to see".
Video developed from facsimile systems developed in the mid-19th century. Mechanical video scanners, such as the Nipkow disk, were patented as early as 1884, but it took several decades before practical video systems could be developed. Whereas the medium of film records using a sequence of miniature photographic images visible to the naked eye, video encodes images electronically, turning them into analog or digital electronic signals for transmission and recording.
Video was originally exclusively live technology, and was first developed for mechanical television systems. These were quickly replaced by cathode-ray tube (CRT) television systems. Live video cameras used an electron beam, which would scan a photoconductive plate with the desired image and produce a voltage signal proportional to the brightness in each part of the image. The signal could then be sent to televisions, where another beam would receive and display the image. Charles Ginsburg led an Ampex research team to develop one of the first practical video tape recorders (VTR). In 1951, the first of these captured live images from television cameras by writing the camera's electrical signal onto magnetic videotape. VTRs sold for around US$50,000 in 1956, and videotapes cost US$300 per one-hour reel. However, prices gradually dropped over the years, and in 1971, Sony began selling videocassette recorder (VCR) decks and tapes into the consumer market.
Digital video is capable of higher quality and, eventually, a much lower cost than its analog predecessor. After the commercial introduction of the DVD, in 1997, and later the Blu-ray Disc, in 2006, sales of videotape and recording equipment fell. Advances in computer technology allow even inexpensive personal computers and smartphones to capture, store, edit, and transmit digital video, further reducing the cost of video production and allowing programmers and broadcasters to move to tapeless production. The advent of digital broadcasting and the subsequent digital television transition are in the process of relegating analog video to the status of a legacy technology in most parts of the world. The development of high-resolution video cameras with improved dynamic range and broader color gamuts, along with the introduction of high-dynamic-range digital intermediate data formats with improved color depth, has caused digital video technology to converge with film technology. Since 2013, the use of digital cameras in Hollywood has surpassed the use of film cameras.
Frame rate—the number of still pictures per unit of time—ranges from six or eight frames per second (frame/s or fps) for older mechanical cameras to 120 or more for new professional cameras. The PAL and SECAM standards specify 25 fps, while NTSC specifies 29.97 fps. Film is shot at a slower frame rate of 24 frames per second, which slightly complicates the process of transferring film to video. The minimum frame rate to achieve persistence of vision (the illusion of a moving image) is about 16 frames per second.
Video can be interlaced or progressive. 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 the optimum spatial resolution of both the stationary and moving parts of the image. 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. Interlacing retains detail while requiring lower bandwidth compared to progressive scanning.
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Video
Video is an electronic medium for the recording, copying, playback, broadcast, and display of moving-image media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) systems, which, in turn, were replaced by flat-panel displays.
Video systems vary in display resolution, aspect ratio, refresh rate, color reproduction, and other qualities. Both analog and digital video can be carried on a variety of media, including radio, magnetic tape, optical discs, computer files, and network streaming.
The word video comes from the Latin video, "I see," the first-person singular present indicative of videre, "to see".
Video developed from facsimile systems developed in the mid-19th century. Mechanical video scanners, such as the Nipkow disk, were patented as early as 1884, but it took several decades before practical video systems could be developed. Whereas the medium of film records using a sequence of miniature photographic images visible to the naked eye, video encodes images electronically, turning them into analog or digital electronic signals for transmission and recording.
Video was originally exclusively live technology, and was first developed for mechanical television systems. These were quickly replaced by cathode-ray tube (CRT) television systems. Live video cameras used an electron beam, which would scan a photoconductive plate with the desired image and produce a voltage signal proportional to the brightness in each part of the image. The signal could then be sent to televisions, where another beam would receive and display the image. Charles Ginsburg led an Ampex research team to develop one of the first practical video tape recorders (VTR). In 1951, the first of these captured live images from television cameras by writing the camera's electrical signal onto magnetic videotape. VTRs sold for around US$50,000 in 1956, and videotapes cost US$300 per one-hour reel. However, prices gradually dropped over the years, and in 1971, Sony began selling videocassette recorder (VCR) decks and tapes into the consumer market.
Digital video is capable of higher quality and, eventually, a much lower cost than its analog predecessor. After the commercial introduction of the DVD, in 1997, and later the Blu-ray Disc, in 2006, sales of videotape and recording equipment fell. Advances in computer technology allow even inexpensive personal computers and smartphones to capture, store, edit, and transmit digital video, further reducing the cost of video production and allowing programmers and broadcasters to move to tapeless production. The advent of digital broadcasting and the subsequent digital television transition are in the process of relegating analog video to the status of a legacy technology in most parts of the world. The development of high-resolution video cameras with improved dynamic range and broader color gamuts, along with the introduction of high-dynamic-range digital intermediate data formats with improved color depth, has caused digital video technology to converge with film technology. Since 2013, the use of digital cameras in Hollywood has surpassed the use of film cameras.
Frame rate—the number of still pictures per unit of time—ranges from six or eight frames per second (frame/s or fps) for older mechanical cameras to 120 or more for new professional cameras. The PAL and SECAM standards specify 25 fps, while NTSC specifies 29.97 fps. Film is shot at a slower frame rate of 24 frames per second, which slightly complicates the process of transferring film to video. The minimum frame rate to achieve persistence of vision (the illusion of a moving image) is about 16 frames per second.
Video can be interlaced or progressive. 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 the optimum spatial resolution of both the stationary and moving parts of the image. 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. Interlacing retains detail while requiring lower bandwidth compared to progressive scanning.