Abbreviated video resolution specifications often include an i to indicate interlacing. NTSC, PAL and SECAM are interlaced formats. 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 of rapidly moving parts of the image when viewed on an interlaced CRT display. Analog display devices reproduce each frame, effectively doubling the frame rate as far as perceptible overall flicker is concerned. In interlaced video, 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. Interlacing retains detail while requiring lower bandwidth compared to progressive scanning.
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. 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. In progressive scan systems, each refresh period updates all scan lines in each frame in sequence. The minimum frame rate to achieve a comfortable illusion of a moving image is about sixteen frames per second. Film is shot at the slower frame rate of 24 frames per second, which slightly complicates the process of transferring a cinematic motion picture to video.
PAL standards (Europe, Asia, Australia, etc.) and SECAM (France, Russia, parts of Africa etc.) specify 25 frame/s, while NTSC standards (USA, Canada, Japan, etc.) specify 29.97 frame/s.
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Characteristics of video streams Number of frames per second įrame rate, the number of still pictures per unit of time of video, ranges from six or eight frames per second ( frame/s) for old mechanical cameras to 120 or more frames per second for new professional cameras. Since 2013, the usage of digital cameras in Hollywood has surpassed film's. The development of high-resolution video cameras with improved dynamic range and 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. 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. Advances in computer technology allows even inexpensive personal computers and smartphones 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.
After the invention of the DVD in 1997, and later the Blu-ray Disc in 2006, sales of videotape and recording equipment plummeted. ĭigital video was later capable of higher quality and, eventually, much lower cost than earlier analog technology. DCT coding was adapted into motion-compensated DCT video compression in the late 1980s, starting with H.261, the first practical digital video coding standard. Practical digital video was made possible with discrete cosine transform (DCT) coding, a lossy compression process developed in the early 1970s. It could not initially compete with analog video, due to early digital uncompressed video requiring impractically high bitrates. The use of digital techniques in video created digital video. See also: Digital television and Video coding format
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