Video compression

Video compression deals with the compression of digital video data. Video compression is necessary for efficient coding of video data in video file formats and streaming video formats.

Video is basically a three-dimensional array of color pixels. Two dimensions serve as spatial (horizontal and vertical) directions of the moving pictures, and one dimension represents the time domain.

A frame is a set of all pixels that (approximately) correspond to a single point in time. Basically, a frame is the same as a still picture. However, in interlaced video, the set of horizontal lines with even numbers and the set with odd numbers are grouped together in fields. The term "picture" can refer to a frame or a field.

However, video data contains spatial and temporal redundancy. Video compression typically reduces this redundancy using lossy compression. Usually this is achieved by image compression techniques to reduce spatial redundancy from frames and motion compensation techniques to reduce temporal redundancy.

In broadcast engineering, digital television (both DVB and ATSC) is made practical by video compression. TV stations can broadcast not only HDTV, but multiple virtual channels on the same physical channel as well. It also conserves precious bandwidth on the radio spectrum.

Video compression

See also