Re: csound surround module: 8chan decoding
| Date | 1999-08-25 01:19 |
| From | Rich Weisgerber |
| Subject | Re: csound surround module: 8chan decoding |
|
I'm in way over my head on this but. .
.
page 321-322 of "Computer Music" (book) by Dodge
& Jerse (ISBN 0-02-864682-7) shows this instead.
I'm in the same boat you are,
Torsten, and haven't figured this part out yet but here's what they
say regarding B-format encode/decode.
Ambisonics B-format encode: X = S *
cos(aa) * cos(ea)Y = S * sin(aa) * cos(ea)
Z = S * sin(ea)
W = 1/sqrt(2) * S
where:
S = input signal
aa = Azimuthal Angle
ea = Elevation Angle
Ambisonics B-format decode:
LFU = W + 1/sqrt(2) * (X + Y + Z)
RFU = W + 1/sqrt(2) * (X - Y + Z)
LBU = W + 1/sqrt(2) * (-X + Y + Z)
RBU = W + 1/sqrt(2) * (-X - Y + Z)
LFD = W + 1/sqrt(2) * (X + Y - Z)
RFD = W + 1/sqrt(2) * (X - Y - Z)
LBD = W + 1/sqrt(2) * (-X + Y - Z)
RBD = W + 1/sqrt(2) * (-X - Y - Z)
where:
L= Left
R = Right
F = Front
B = Back
U = Up
D = Down
I still don't have a very good handle on what W is, some kind of
Omnidirectional characteristic, but Huh?
W isn't quite clicking in my head yet.. ;-)
X, Y, & Z are cartesian coordinates for the location of individual
sound source, yes?
I imagine further discussion on whether this is accurate belongs in
sursound list as they Are Ambisonics over there.
They'd probably be able to give us some clues on the licensing aspects of
this information and how it's used foir what purpose.
However, I am also interested in getting this working in Csound for my own
work, even at my inherent snail's pace. We'll see how this goes... or not..
;-)
r out
|
| Date | 1999-08-25 17:01 |
| From | "Matt J. Ingalls" |
| Subject | Re: csound surround module: 8chan decoding |
im probably not the best to respond to all this, but oh well: > page 321-322 of "Computer Music" (book) by Dodge & Jerse (ISBN 0-02-864682-7) shows this instead. wow. im surprised its in there! > > Ambisonics B-format encode: i might point out that this encode formula is for panning a mono source, which i am guessing would sound pretty much like a chowning-type "mover" orchestra...(although you have the speakers working together rather than just 1 or2) there are methods to take a mono source and synthesize image "width" - but maybe someone else would be better to explain this... > > I still don't have a very good handle on what W is, some kind of >Omnidirectional characteristic, but Huh? yes - one way to think of it is as 4 microphones stacked on top of each other: 3 figure of 8s pointed forward, left, and up and one omni. (basically thats what i soundfield mic does - although i think the capsules are arranged in a tetragon[or whatever the 4 sided regular polygon-thing is called] and then does a translation to B-Format) > > I imagine further discussion on whether this is accurate belongs in >sursound list as they Are Ambisonics over there. it doesnt really occur that much on sursound list (but it should!) - most of sursound list talk is about recording/etc.. not synthesis/manipulation/etc > They'd probably be able to give us some clues on the licensing aspects >of this information and how it's used foir what purpose. as far as i understand, B-format/etc patent has run out and is public domain - the only current patents exist for converting B-Format into Dolby Surrond (g-Format) > -matt |