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https://github.com/cookiengineer/audacity
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128 lines
4.4 KiB
Common Lisp
128 lines
4.4 KiB
Common Lisp
;nyquist plug-in
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;version 3
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;type process
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;categories "http://lv2plug.in/ns/lv2core#DelayPlugin"
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;name "Delay..."
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;action "Applying Delay Effect..."
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;; by Steve Daulton, July 2012.
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;; based on 'Delay' by David R. Sky
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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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;;
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;; For information about writing and modifying Nyquist plug-ins:
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;; http://wiki.audacityteam.org/wiki/Nyquist_Plug-ins_Reference
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;control delay-type "Delay type" choice "regular,bouncing ball,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 "Pitch/Tempo,LQ 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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(setf err "") ; initialise error message
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(defun err-chk (arg min max)
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(if (or (< arg min) (> arg max))
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T nil))
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(when (err-chk number 1 50)(setq err (format nil
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"Number of echoes '~a' outside valid range 1 to 50.~%~a"
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number err)))
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(when (err-chk shift -12 12)(setq err (format nil
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"Pitch change '~a' outside valid range -12 to +12 semitones.~%~a"
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shift err)))
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(when (err-chk delay 0 10)(setq err (format nil
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"Delay time '~a' outside valid range 0 to 10 seconds.~%~a"
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delay err)))
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(when (err-chk dgain -30 6)(setq err (format nil
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"Delay level '~a' outside valid range -30 to +6 dB.~%~a"
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dgain err)))
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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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;;; return errors or process
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(if (> (length err) 0)
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(format nil "Error.~%~a" err) ; return error
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(let* ((delay (if (= delay-type 0) delay (/ delay number)))
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(output
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(multichan-expand #'delays
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s dgain delay shift number delay-type 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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