Dolby Digital
A family of multi-channel audio codecs/audio compression technologies from Dolby Laboratories, based on AC-3 technology. Dolby Digital includes several similar technologies, such as Dolby Digital EX, Dolby Digital Live, and Dolby Digital Plus. The most common of these is simply called 'Dolby Digital' which contains up to six discrete channels of sound. The most elaborate mode in common usage involves five channels for normal-range speakers (20 Hz – 20,000 Hz) (right front, centre, left front, right rear and left rear) and one channel (20 Hz – 120 Hz allotted audio) for the subwoofer driven low-frequency effects.