Video

Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media.

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 broadcasts, magnetic tape, optical discs, computer files, and network streaming.

[4] Charles Ginsburg led an Ampex research team to develop one of the first practical video tape recorders (VTR).

[5] However, prices gradually dropped over the years; in 1971, Sony began selling videocassette recorder (VCR) decks and tapes into the consumer market.

[6] Digital video is capable of higher quality and, eventually, a much lower cost than earlier analog technology.

After the commercial introduction of the DVD in 1997 and later the Blu-ray Disc in 2006, sales of videotape and recording equipment plummeted.

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 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.

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.

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.

For example, PAL video format is often described as 576i50, where 576 indicates the total number of horizontal scan lines, i indicates interlacing, and 50 indicates 50 fields (half-frames) per second.

Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material.

A variety of methods are used to compress video streams, with the most effective ones using a group of pictures (GOP) to reduce spatial and temporal redundancy.

Likewise, temporal redundancy can be reduced by registering differences between frames; this task is known as interframe compression, including motion compensation and other techniques.

The most common modern compression standards are MPEG-2, used for DVD, Blu-ray, and satellite television, and MPEG-4, used for AVCHD, mobile phones (3GP), and the Internet.

Broadcast or studio cameras use a single or dual coaxial cable system using serial digital interface (SDI).

Early television was almost exclusively a live medium, with some programs recorded to film for historical purposes using Kinescope.

[24][26] Optical storage mediums offered an alternative, especially in consumer applications, to bulky tape formats.