🚀 go-pugleaf

Dan Frankowski (dfrankow@myria.cs.umn.edu) wrote:
: Neat.  Let me clarify my application.  I'd like to do audio
: teleconferencing on a packet-switched network.  With this I'd like to
: place the different people in the conference in different places in
: the audio space.  This would make it easier to separate what people
: were saying.  I'm not sure separating midrange and high/low range
: would work well for voices.

I don't think it would work at all.  It only adds a bit of "spread"
to musical sound (and not very realistically, either).

Are you talking about two-way or N-way teleconferencing?  If it's
something like an audio "Internet chat" program (that is, N-way), with
one talker per station, then you simply place each data stream at a
different place in the stereo field at the receiving end with something
like:

	L = S*P
	R = S*(1-P)

Where "P" is some arbitrary position between 0 and 1, "S" is the
data stream for a particular talker, and "L" and "R" are the left
and right channels, respectively.  Thus, the talker assigned 0.5
would be right in the middle, while 0, 0.25, 0.75, and 1.0 would
be hard right, mid right, mid left, and hard left, respectively.

If this is a two-way teleconference, or some other setup where you
have more than one talker per station, you have to have more than
one microphone, and actually transmit position information based on
which microphone has the loudest input at a given moment.  This
is then fed into P on the receiving end.

: That leads to another question of mine.  Is there code for band reject
: and band pass filters out there?  I realize that filters should be
: specially tailored to the application.  However, since I don't know
: much DSP, I'd love to just try filters with certain specified
: tolerances.  I've read the FAQ without much luck.

Look in "Musical Application of Microprocessors," 2nd Ed. (by Hal
Chamberlin, Hayden Books, 1985, ISBN 0-8104-5768-7) for some practical,
non-mathematical material on the subject (and on stereo, too).  Some of
the DSP programming texts will also provide enough info to serve as a
cookbook.  But you really aren't going to get much beyond the cookbook
stage without a background in engineering mathematics--which might not
be a problem, depending upon your application(s).

		-Ed Hall
		edhall@rand.org