Dolby Digital Surround Sound is an advanced form of digital audio coding that makes it possible to store and transmit high-quality digital sound efficiently. It gives listeners and viewers a more realistic feeling.
Dolby Digital 5.1 Surround Sound is an audio coding technique capable of delivering sound with five discrete full-range channels--left, center and right surround--plus a sixth channel for those powerful low-frequency effects that are felt more than heard in movie theaters. This is commonly known as the subwoofer. The subwoofer needs only about one-tenth the space of the others and is referred to as a ".1" channel. Therefore, the entire group of channels is named Dolby Digital 5.1 Surround Sound.
Dolby Pro Logic features four channels: front left, center, front right and a mono surround channel that is usually split between two rear speakers.