66 lines
1.8 KiB
Text
66 lines
1.8 KiB
Text
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#lang scribble/manual
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@(require (for-label racket))
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@title{(pvcollect chain numframes func frombin tobin zeroothers)}
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Process each bin of an fft chain separately.
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pvcollect applies function func to each bin of an fft chain. func
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should be a function that takes magnitude, phase, index as inputs
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and returns a resulting [magnitude, phase].
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The "index" is the integer bin number, starting at 0 for DC. You
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can optionally ignore the phase and only return a single
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(magnitude) value, in which case the phase is assumed to be left
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unchanged.
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frombin, tobin, and zeroothers are optional arguments which limit
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the processing to a specified integer range of fft bins. If
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zeroothers is set to 1 then bins outside of the range being
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processed are silenced.
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Note that this procedure can be relatively CPU-heavy, depending on
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how you use it.
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(define no-op
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(lambda (m p _)
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(list m p)))
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(define rand-phase
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(lambda (m p _)
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(list m (rand 0 3.14))))
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(define noise-phase
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(lambda (m p _)
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(list m (lin-lin (lf-noise0 kr 3) -1 1 0 3.14))))
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(define combf
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(lambda (m p i)
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(list (if (= (modulo i 7) 0) m 0) p)))
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(define noise-mag
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(lambda (m p _)
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(list (mul (gt (lf-noise0 kr 10) 0) m) p)))
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(define spectral-delay
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(lambda (m p _)
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(let ((v (lin-lin (lf-par kr 0.5 0) -1 1 0.1 1)))
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(list (add m (delay-n m 1 v)) p))))
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(define (bpf-sweep nf)
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(lambda (m p i)
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(let ((e (u:abs (sub i (lin-lin (lf-par kr 0.1 0) -1 1 2 (/ nf 20))))))
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(list (mul (lt e 10) m) p))))
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(with-sc3
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(lambda (fd)
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(async fd (b-alloc 10 1024 1))
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(async fd (b-alloc-read 11 "/home/rohan/audio/metal.wav" 0 0))))
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(let* ((nf 1024)
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(i (play-buf 1 11 (buf-rate-scale kr 11) 1 0 1))
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(c1 (fft* 10 i))
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(c2 (pvcollect c1 nf spectral-delay 0 250 0)))
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(audition (out 0 (mul 0.1 (ifft* c2)))))
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