Often referred to as ‘5.1’, this reproduces six separate (discrete) channels – Left, Center, Right, Left Rear, Right Rear, and sub-woofer (the .1). All the five main channels have full frequency response which, together with a separate low-frequency sub-woofer, create a three-dimensional effect. Only one sub-woofer is required because the human ear is not directional at low frequencies. Discrete 7.1 Audio is similar but includes more speakers.
Discrete 5.1 audio is made available with many HD television broadcasts and is specified on HD DVD and BD media.
See also: Dolby Digital