60 lines
1.7 KiB
Racket
60 lines
1.7 KiB
Racket
#lang scribble/manual
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@(require (for-label racket))
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@title{(rotate2 x y pos)}
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Rotate a sound field. rotate2 can be used for rotating an
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ambisonic B-format sound field around an axis. rotate2 does an
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equal power rotation so it also works well on stereo sounds. It
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takes two audio inputs (x, y) and an angle control (pos). It
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outputs two channels (x, y).
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It computes:
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xout = cos(angle) * xin + sin(angle) * yin;
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yout = cos(angle) * yin - sin(angle) * xin;
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where angle = pos * pi, so that -1 becomes -pi and +1 becomes +pi.
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This allows you to use an lf-saw to do continuous rotation around a
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circle.
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The control pos is the angle to rotate around the circle from -1
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to +1. -1 is 180 degrees, -0.5 is left, 0 is forward, +0.5 is
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right, +1 is behind.
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@racketblock[
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(let* ((p (mul (white-noise ar) 0.05))
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(q (mul (mix (lf-saw ar (make-mce (list 200 200.37 201)) 0)) 0.03))
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(encoded (add (pan-b2 p -0.5 1) (pan-b2 q -0.5 1)))
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(rotated (rotate2 (mce-channel encoded 1)
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(mce-channel encoded 2)
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(mouse-x kr -1 1 0 0.1)))
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(decoded (decode-b2 4
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(mce-channel encoded 0)
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(mce-channel rotated 0)
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(mce-channel rotated 1)
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0.5)))
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(audition (out 0 decoded)))
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]
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Rotation of stereo sound, via LFO.
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@racketblock[
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(let ((x (mul (pink-noise ar) 0.4))
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(y (mul (lf-tri ar 800 0) (mul (lf-pulse kr 3 0 0.3) 0.2))))
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(audition (out 0 (rotate2 x y (lf-saw kr 0.1 0)))))
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]
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Rotation of stereo sound, via mouse.
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@racketblock[
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(let ((x (mix-fill 4 (lambda (_) (mul (lf-saw ar (rand 198 202) 0) 0.1))))
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(y (mul (sin-osc ar 900 0) (mul (lf-pulse kr 3 0 0.3) 0.2))))
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(audition (out 0 (rotate2 x y (mouse-x kr 0 2 0 0.1)))))
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]
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