What is the difference between Dolby Surround and Dolby Digital?
The Pro Logic, or Dolby Surround, sound heard on videotapes and laser discs in the past is what’s called a “matrixed” soundtrack. The left, center, right and surround tracks are combined into two channels in the studio, then decoded by the Pro Logic receiver out to the original four in the home theater. But Pro Logic doesn’t give stereo surrounds like Dolby Digital. Dolby Digital provides “discrete” channels of information that aren’t combined then extracted again like Pro Logic. Though the original channels are combined into a bitstream, the information is compressed instead of “matrixed.” Thus, 5.1-channel Dolby Digital soundtracks provide stereo surrounds, and the channels don’t bleed into one another.
