Definitions for "Dolby® Digital"
The digital audio format used on the large majority of DVDs, all HDTV programs, and selected satellite TV broadcasts, Dolby Digital can include from one to six channels of sound. "5.1-channel" Dolby Digital has 6 discrete digital audio channels: 5 full-bandwidth channels (for front left/right, center, and surround left/right) and 1 "low frequency effects" subwoofer channel.
A discrete, multichannel digital audio standard offering enhanced sonic realism. Dolby Digital is normally associated with 5.1-channel surround sound. A 5.1-channel system offers five full-bandwidth channels (including true stereo surrounds), plus a "low frequency effects" subwoofer channel.
An audio signal encoding/decoding system, developed by Dolby Laboratories, that uses perceptual coding to reduce the data rate required to transmit, and the amount of digital space required to store, digital audio signals. Different consumer and professional versions use different amounts of compression, and therefore have different levels of audio quality. It can store mono, stereo and multichannel formats. See Perceptual Coding