Video compression

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

Notions: video is basically a three-dimensional array of color pixels. Two dimensions serve as spacial (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 to fields. The term picture can refer to a frame or a field.

Method: 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.