What is Dolby Digital (AC-3) &Dolby® Pro-Logic ?

Dolby Digital (AC-3)
Using a special encoding and decoding process, Dolby Digital allows the movie producer to place full-range dialog, music, and effects anywhere in the listening environment. In order to enjoy Dolby Digital (also know as AC-3) a processor capable of decoding the digital signal must be used. DVD players, Laser Disc Players, DSS receivers, and HDTV set-top boxes are all capable of providing you with the source material for Dolby Digital surround sound.

Dolby® Pro-Logic
Dolby Laboratories developed the process to take two channels of information (stereo) from a source such as a VCR or Laser Disc player, and send it though an electronic network to produce the two additional channels that give us "surround sound". Dolby Pro-Logic is an analog process and will allow us to utilize a center channel for dialog, and two monaural rear speakers. Although a drastic improvement from the original "Dolby Surround," which did not include a center channel, the rear channel information is limited in frequency response and does not allow left to right "panning" in the rear speakers.