All surround sound formats work by first encoding the audio information onto a programming source, such as a DVD or television broadcast. When the programming is played, the surround sound tracks are extracted from the source by a piece of electronics called a surround decoder. The individual surround channels are then amplified and fed to the appropriate speakers.
Matrix surround sound systems work by blending center and surround channel information into the standard left and right channels of a stereo soundtrack. The surround decoder extracts the center and surround channels by identifying them as information different from the standard left/right channel data. Dolby Pro Logic is the most common matrix technology.
Discrete surround sound systems keep each audio channel completely separate throughout the entire process. The surround decoder simply has to read the individual audio tracks and send them to the appropriate amplifiers. The discrete approach offers near-perfect channel separation, resulting in better audio imaging and frequency response than a matrix system. Dolby Digital and DTS are the most popular discrete technologies.
Dolby Digital EX and DTS ES add sixth and seventh rear channels by matrixing their information onto the existing left and right surround channels. DTS ES Discrete adds a sixth channel using discrete technology.