Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode ray tube (CRT) systems which were later replaced by flat panel displays of several types. Video systems vary in display resolution, aspect ratio, refresh rate, color capabilities and other qualities. Analog and digital variants exist and can be carried on a variety of media, including radio broadcast, magnetic tape, optical discs, computer files, and network streaming.
The use of digital techniques in video created digital video. It could not initially compete with analog video, due to early digital uncompressed video requiring impractically high bitrates. Practical digital video was made possible with discrete cosine transform (DCT) coding, a lossy compression process developed in the early 1970s. 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.
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. Video was originally exclusively a live technology. Charles Ginsburg led an Ampex research team developing one of the first practical video tape recorder (VTR). In 1951 the first VTR captured live images from television cameras by writing the camera’s electrical signal onto magnetic videotape. Video recorders were sold for US$50,000 in 1956, and videotapes cost US$300 per one-hour reel. However, prices gradually dropped over the years; in 1971, Sony began selling videocassette recorder (VCR) decks and tapes into the consumer market.