What is MPEG compression?

MPEG is a series of audio and video compression standards defined by the Motion Picture Experts Group of the International Standards Organisation.

Both MPEG audio and video compression rely on losing some information in order to reduce the data rate - the information to discard is chosen to be the least readily perceived by the human hearing or visual systems. The reduced data is then compressed with lossless data compression techniques.

MPEG audio compression depends on matching the representation of the audio data to the sensitivity of the human ear, and is based upon a 'psychoacoustic' model of the human ear. Since the human ear responds to frequencies, information can be condensed without much perceived loss by coding in the frequency domain.

MPEG video compression relies on the fact that the human eye is less sensitive to variations in color than in brightness, and so color information can be coded with less accuracy. MPEG video compression also uses a technique of motion prediction - so that if an object moves between frames of a video sequence the details of the movement can be sent rather than an entire image of the object itself. Images are also compressed by analysing their frequency content (sort of, a measure of their fine detail) and coding so that some fine detail is discarded.

The MPEG standards deal with compression of combined audio and video signals, and so synchronisation between the audio and the video information is important.