Rotate2 Rotate a sound field


Rotate2.kr(x, y, pos)


Rotate2 can be used for rotating an ambisonic B-format sound field around an axis.

Rotate2 does an equal power rotation so it also works well on stereo sounds.

It takes two audio inputs (x, y) and an angle control (pos).

It outputs two channels (x, y).

It computes this:


xout = cos(angle) * xin + sin(angle) * yin;

yout = cos(angle) * yin - sin(angle) * xin;


where angle = pos * pi,  so that -1 becomes -pi and +1 becomes +pi. 

This allows you to use an LFSaw to do continuous rotation around a circle.


x, y - input signals

pos - angle to rotate around the circle from -1 to +1. 

-1 is 180 degrees, -0.5 is left, 0 is forward, +0.5 is right, +1 is behind.


(

{

var w, x, y, p, q, a, b, c, d;

p = WhiteNoise.ar(0.05); // source

q = LFSaw.ar(200,0,0.03)+LFSaw.ar(200.37,0,0.03)+LFSaw.ar(201,0,0.03);

// B-format encode 2 signals at opposite sides of the circle

#w, x, y = PanB2.ar(p, -0.5) + PanB2.ar(q, 0.5); 

#x, y = Rotate2.ar(x, y, MouseX.kr(-1,1));

// B-format decode to quad

#a, b, c, d = DecodeB2.ar(4, w, x, y);

[a, b, d, c] // reorder to my speaker arrangement: Lf Rf Lr Rr

}.play;

)




// Rotation of stereo sound:

(

{

// rotation via lfo

var x, y;

x = PinkNoise.ar(0.4);

y = LFTri.ar(800) * LFPulse.kr(3,0,0.3,0.2);

#x, y = Rotate2.ar(x, y, LFSaw.kr(0.1));

[x,y]

}.play;

)


{

// rotation via mouse

var x, y;

x = Mix.fill(4, { LFSaw.ar(200 + 2.0.rand2, 0, 0.1) });

y = SinOsc.ar(900) * LFPulse.kr(3,0,0.3,0.2);

#x, y = Rotate2.ar(x, y, MouseX.kr(0,2));

[x,y]

}.play;



// Rotate B-format about Z axis:


wout = win;

zout = zin;

#xout, yout = Rotate2.ar(xin, yin, pos);


// Rotate B-format about Y axis:


wout = win;

yout = yin;

#xout, zout = Rotate2.ar(xin, zin, pos);


// Rotate B-format about X axis:


wout = win;

xout = xin;

#yout, zout = Rotate2.ar(yin, zin, pos);




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