150 lines
4.6 KiB
Common Lisp
150 lines
4.6 KiB
Common Lisp
$nyquist plug-in
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$version 4
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$type process
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$name (_ "Limiter")
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$manpage "Limiter"
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$debugbutton false
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$action (_ "Limiting...")
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$preview enabled
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$author (_ "Steve Daulton")
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$release 2.3.0
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$copyright (_ "Released under terms of the GNU General Public License version 2")
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;; limiter.ny by Steve Daulton November 2011, updated May 2015.
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;; Released under terms of the GNU General Public License version 2:
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;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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;;
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;; For information about writing and modifying Nyquist plug-ins:
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;; https://wiki.audacityteam.org/wiki/Nyquist_Plug-ins_Reference
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$control type (_ "Type") choice (
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("SoftLimit" (_ "Soft Limit"))
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("HardLimit" (_ "Hard Limit"))
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;i18n-hint: clipping of wave peaks and troughs, not division of a track into clips
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("SoftClip" (_ "Soft Clip"))
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("HardClip" (_ "Hard Clip"))
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) 0
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$control gain-L (_ "Input Gain (dB)
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mono/Left") real "" 0 0 10
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$control gain-R (_ "Input Gain (dB)
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Right channel") real "" 0 0 10
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$control thresh (_ "Limit to (dB)") real "" -3 -10 0
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$control hold (_ "Hold (ms)") real "" 10 1 50
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$control makeup (_ "Apply Make-up Gain") choice (
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(_ "No")
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(_ "Yes")
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) 0
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(if (not (boundp 'type))
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(setf type 0))
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(if (boundp 'gain-L)
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(setf gain-L (db-to-linear gain-L))
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(setf gain-L 1))
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(if (boundp 'gain-R)
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(setf gain-R (db-to-linear gain-R))
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(setf gain-R 1))
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(if (boundp 'thresh)
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(setf thresh (db-to-linear thresh))
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(setf thresh (db-to-linear -3.0)))
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(if (not (boundp 'hold))
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(setf hold 10.0))
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(if (boundp 'makeup)
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(if (= makeup 1) (setf makeup T) (setf makeup nil))
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(setf makeup nil))
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;;; brick wall limiter
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(defun hardlimit (sig limit hld)
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(let* ((time (/ hld 3000.0)) ; lookahead time (seconds)
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(samples (round (* time *sound-srate*))) ; lookahead in samples
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(peak-env (get-env sig samples time limit)))
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(mult sig
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(snd-exp
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(mult -1 (snd-log peak-env))))))
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;;; Envelope follower for brick wall limiter
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(defun get-env (sig step lookahead limit)
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(let* ((sig (mult (/ limit) sig))
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(pad-time (* 3 lookahead)) ; padding required at start (seconds)
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(pad-s (* 3 step)) ; padding samples
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(padding (snd-const (peak sig pad-s) 0 *sound-srate* pad-time))
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(peak-env (snd-avg sig (* 4 step) step OP-PEAK)))
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(extract 0 1
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(s-max 1
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(sim padding
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(at-abs pad-time (cue peak-env)))))))
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(defun softlimit (sig thresh hld)
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(let* ((sig (hardlimit sig 1 hold))
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(step (truncate (* (/ hld 3000.0) *sound-srate*)))
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(waveshape (snd-avg sig (* 4 step) step op-peak))
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(env (sum thresh (mult thresh (diff 1 waveshape))))
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(env (clip env 1))
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(offset (/ (* 3 step) *sound-srate*))
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(initial (peak sig (* 2 step)))
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(pause-lev (sum thresh (mult thresh (diff 1 initial))))
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(pause-lev (clip pause-lev 0.9))
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(pause (snd-const pause-lev 0 *sound-srate* offset)))
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(setf env
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(sim
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pause
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(at-abs offset (cue env))))
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(mult sig env)))
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(defun soft-clip-table ()
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"Lookup table for soft clipping wave-shaper"
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(abs-env
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(sound-srate-abs 44100
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(Control-srate-abs 44100
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(let* ((knee (- 1 (/ 1.0 pi)))
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(kcurve (mult knee (osc (hz-to-step (/ (* 4 knee))) knee)))
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(ikcurve (mult knee (osc (hz-to-step (/ (* 4 knee))) knee *sine-table* -90)))
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(lin (pwlv -0.5 knee -0.5
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(+ knee (/ 2.0 pi)) 0.5
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2.0 0.5
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2.0 (+ 0.5 knee)
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2.1 (+ 0.5 knee))))
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(mult (/ 2.0 pi)
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(sim
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(at-abs 0 (cue ikcurve))
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(at-abs 0 (cue lin))
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(at-abs (+ knee (/ 2.0 pi)) (cue kcurve)))))))))
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(defun soft-clip (sig)
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(let* ((knee (- 1 (/ 1.0 pi)))
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(clip-level (* (+ 0.5 knee)(/ 2.0 pi)))
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(sig (mult clip-level (/ thresh) sig)))
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(if makeup
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(mult 0.999
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(/ clip-level)
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(shape sig (soft-clip-table) 1.0))
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(mult thresh
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(/ clip-level)
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(shape sig (soft-clip-table) 1.0)))))
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(defun makupgain (sig)
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(if makeup
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(mult (/ 0.999 thresh) sig) ;keep below 0dB
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sig))
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;; Pre-gain
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(setf *track*
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(if (arrayp *track*)
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(vector (mult (aref *track* 0) gain-L)
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(mult (aref *track* 1) gain-R))
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(mult *track* gain-L)))
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(case type
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(0 (makupgain (multichan-expand #'softlimit *track* thresh hold)))
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(1 (makupgain (multichan-expand #'hardlimit *track* thresh hold)))
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(2 (soft-clip *track*))
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(T (makupgain (clip *track* thresh))))
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