Pro Logic - How does it work?

[Killean]

Just how does Dolby Digital Pro Logic II work exactly? How does it manage to take a standard stereo connection and differentiate between what should be front and surround noises (front and rear speakers)?

 

I tried a few google searches but never came across any definitive answers on the subject. Many thanks to whomever can help me on this.

[pgrmdave]

http://www.dolby.com/consumer/technology/prologic_II.html

A matrix surround decoding technology, Dolby Pro Logic II detects the directional cues that occur naturally in stereo content and uses these elements to create a five-channel surround sound playback experience.

 

I don't know if this answers your question, but I couldn't find anything else online.

[Killean]

Not quite the indepth look that I need, or might be my lack of audio engineering. I suppose the information about what exactly these directional cues entail is a guarded secret by them and anyone who buys the rights to the knowledge to use in games, movies, music...

 

Thank you nonetheless Dave.

[GAHD]

sounds like they just map a sound range (just like you do with an eqiliser), and then they figure out what amplitute of each frequency range is pumped to each speaker channel. then they map that onto the 5 speakers.

 

I'd bet something shared between the two close to eqilly is pumped to center, with stuff that's just one or the other is pumped to the rear set, and with what's shared being filtered out.

[alexander]

i think this might help:

http://stuffo.howstuffworks.com/surround-sound.htm

[Killean]

Thank you Alex for that link. It eventialy led me to here: http://www.dolby.com/resources/tech_library/index.cfm, which is the technical library for find out a lot more info about how to encode for Dolby Digital Pro Logic II.

[alexander]

Oh, no problem, i guess, welcome any time... :)