Re: REAL GS Surround Sound

[philip@labtam.OZ.AU (Philip Stephens)]

Geoff Weiss writes:

>Philip, you had to write custom code for this, right?

  Well, yes.  Before you get too excited, my surround sound experiment was
just a small program that puts a square wave and it's 180 degree out of
phase counterpart into the Ensoniq RAM, and then allows you to play notes.
It's not a fully-fledged MOD player or anything like that!  I simply wrote
it to test out the theory that the GS could generate a Dolby surround
encoded signal.

> Soundsmith and NT don't have this capability, right?

  Actually, you _could_ use Soundsmith or NT to generate surround sound.
All you would need to do is write a program that takes an instrument file
and inverts the values in the wavetable to produce an instrument that is
180 degrees out of phase compared to the original.  You could then load
both instruments into Soundsmith and NT and have them both play
simultaneously to generate a surround signal.

>Do the oscillators have to be 180 degrees out of phase or can you have 60
>or 90 degrees out of phase and still have the surround sound depth?

  Dolby surround encoding requires that any sounds that are to appear in
the surround channel must appear in both left and right channels of the
stereo signal, 180 degrees out of phase.  The 180 degrees out of phase
bit is important, as it has the property of allowing the surround signal
to be cancelled out simply by "adding" left and right channels together.