The table as given below demonstrates possible values of such parameters for classic applications of digital video.

Application                  Frame rate                  Dimensions                 Pixel Depth

Multimedia                     15                            320 x 240                          16

Entertainment TV            25                            640 x 480                           16

Surveillance                     5                             640 x 480                          12

Video Telephony             10                            320 x 240                           12

HDTV                             25                           1920 x 1080                        24

Progresses in compression technology more than anything else have lead to the entrance of the video to the desktop and hundreds of channels to houses.

Compression is a reversible conversion of data to a format which needs fewer bits, generally performed hence the data can be transmitted or saved more efficiently. The size of data in compressed by (C) relative to the original size (O) is termed as the compression ratio (R=C/O). The compression is lossless, if the inverse of the decompression, process, produces a proper replica of the original data.

Lossy compression, generally applied to image data, does not permit reproduction of a proper replica of the original image, although has a higher compression ratio. Hence, lossy compression permits only an approximation of the original to be produced.

Compression is analogous to folding a letter before putting this in a small envelope hence it can be transported more simply and cheaply as demonstrated in the figure. Compressed data, as the folded letter, is not simply read and should first be decompressed or unfolded to restore this to its original appearance.

The success of data compression based largely upon the data itself and several data types are inherently more compressible than others. Generally some elements inside the data are more general than others and most compression algorithms exploit such property, termed as redundancy. The greater the redundancy inside the data, the more successful the compression of the data is as to be. Fortunately, digital video includes a huge deal of redundancy and thus, is very appropriate for compression.

A device that may be software or hardware which compresses data is frequently termed as an encoder or coder, while a device that decompresses data is termed as a decoder. A device which acts as both a coder and decoder is termed as a codec.