First, AC-3 and Dolby Digital are synonomous - they are the
same thing. [ Actually one refers to the codec and the other
the implementation of that codec, if you want to get real
A Prologic only processor takes a 2 channel stereo signal
that has surround information "matrixed" on it and strips off
the mono surround channel. It also derives the center channel
signal from what is common to the left and right channels.
DD (AC-3) and DTS are 5.1 channel formats. Each has 5 "full"
bandwidth channels - left front, center front, right front,
left rear, right rear - and a limited bandwidth subwoofer
channel [ that's the .1 ]. This is all compressed into a
single digital data stream with MPEG compression.
You need a DD/DTS processor to uncompress this digital data
stream and separate out all the discrete channels. A Dolby
Prologic "processor" is not going to do that.
Dr. Gregory Greenman