Dolby Pro-Logic II

Getting started out in the Home Theater addiction hobby can be quite daunting. Sometimes we all need a bit of the Sesame Street approach to get started. This week, the HT section of about.com, is brought to you by the surround sound format Dolby Pro-Logic II. Similar to other Dolby formats, it is 5 speaker + 1 subwoofer format. However, Pro-Logic II simulates a 5.1 setup and other formats such as Dolby Digital are encoded directly to 5.1.

From the article:

Dolby Pro-Logic II technology can create a "simulated" 5.1 channel surround environment from any two channel source (such as stereo CDs and Vinyl Records) as well as from a 4-Channel Dolby Surround signal.
Although not a discrete format, such as Dolby Digital 5.1 or DTS, in which each channel goes though its own encoding/decoding process, Pro Logic II makes an effective use of matrixing to deliver an adequate 5.1 representation of a stereo film or music soundtrack.