117 lines
4.3 KiB
Common Lisp
117 lines
4.3 KiB
Common Lisp
$nyquist plug-in
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$version 4
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$type process
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$preview linear
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$name (_ "Delay")
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$manpage "Delay"
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$debugbutton false
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$action (_ "Applying Delay Effect...")
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$author (_ "Steve Daulton")
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$release 2.3.1
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$copyright (_ "Released under terms of the GNU General Public License version 2")
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;; Released under terms of the GNU General Public License version 2:
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;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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;; based on 'Delay' by David R. Sky
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;;
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;; For information about writing and modifying Nyquist plug-ins:
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;; https://wiki.audacityteam.org/wiki/Nyquist_Plug-ins_Reference
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$control delay-type (_ "Delay type") choice ((_ "Regular")
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("BouncingBall" (_ "Bouncing Ball"))
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("ReverseBouncingBall" (_ "Reverse Bouncing Ball"))) 0
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$control dgain (_ "Delay level per echo (dB)") real "" -6 -30 1
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$control delay (_ "Delay time (seconds)") real "" 0.3 0 5
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$control pitch-type (_ "Pitch change effect") choice (("PitchTempo" (_ "Pitch/Tempo"))
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("LQPitchShift" (_ "Low-quality Pitch Shift"))) 0
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$control shift (_ "Pitch change per echo (semitones)") real "" 0 -2 2
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$control number (_ "Number of echoes") int "" 5 1 30
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$control constrain (_ "Allow duration to change") choice ((_ "Yes")(_ "No")) 0
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;; The default pitch shift effect is a simple resampling,
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;; so both pitch and tempo of the delayed audio will change
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;; [as in Audacity's Change Speed effect].
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;; LQ Pitch Shift (Low Quality) changes the pitch without
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;; changing the tempo, but the sound quality is not very good
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;; and tends to cause a short echo effect which can be quite
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;; noticeable on percussive sounds though may be acceptable
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;; on other sounds.
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;;; Anti-alias low pass filter
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(defun lp-wall (sig freq)
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(do ((count 0 (1+ count))
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(freq (* 0.94 freq)))
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((= count 10) sig)
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(setf sig (lowpass8 sig freq))))
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;;; Change speed
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(defun change-speed (sig shift)
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(if (= shift 0) ; no pitch shift
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sig
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(let ((ratio (expt 0.5 (/ shift 12.0)))) ; shift value as frequency ratio
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(force-srate *sound-srate*
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(stretch-abs ratio (sound sig))))))
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;;; Pitch shift audio
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(defun p-shift (sig shift)
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(if (= shift 0) ; no pitch shift
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sig
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(let ((sig (force-srate 44100 sig)) ; pitshift quality best at 44100
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; anti-alias filter frequency
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(minrate (* 0.5 (min *sound-srate* 44100)))
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(ratio (expt 0.5 (/ shift -12.0)))) ; shift value as frequency ratio
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(force-srate *sound-srate* ; convert back to correct rate
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(progv '(*sound-srate*) (list 44100) ; pitshift requires rates to match
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(cond
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((> shift 5) ; reduce aliasing
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(pitshift (lp-wall sig (/ minrate ratio)) ratio 1))
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((< shift -2)
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(pitshift (hp sig 20) ratio 1)) ; reduce sub-sonic frequencies
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(T (pitshift sig ratio 1))))))))
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;;; Apply effects to echo
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(defun modify (sig num gain shift p-type)
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(let ((gain (db-to-linear (* num gain)))
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(shift (* num shift)))
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(if (= p-type 0)
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(mult gain (change-speed sig shift))
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(mult gain (p-shift sig shift)))))
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;;; Compute echoes
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(defun delays (sound gain delay shift num type mod)
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(let ((echo (s-rest 0)))
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(do ((count 1 (1+ count))
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(dly 0))
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((> count num)(sim echo sound))
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(setq dly
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(case type
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(0 (+ dly delay))
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(1 (+ dly (* delay (- (1+ num) count))))
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(2 (+ dly (* delay count)))))
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(setf echo (sim
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(at 0 (cue echo))
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(at-abs dly
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(cue (modify sound count gain shift mod))))))))
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(defun constrain-abs (sig dur)
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(extract-abs 0 dur (cue sig)))
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(let* ((delay (if (= delay-type 0)
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delay
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(/ delay number)))
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(output (multichan-expand #'delays *track*
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dgain
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delay
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shift
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number
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delay-type
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pitch-type)))
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(if (= constrain 1)
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(multichan-expand #'constrain-abs output (get-duration 1))
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output))
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