/usr/share/audacity/plug-ins/adjustable-fade.ny is in audacity-data 2.0.5-1ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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;version 3
;type process
;categories "http://lv2plug.in/ns/lv2core#MixerPlugin"
;name "Adjustable Fade..."
;action "Applying Fade..."
;; adjustable-fade.ny by Steve Daulton Dec 2012
;; Released under terms of the GNU General Public License version 2:
;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;;
;; For information about writing and modifying Nyquist plug-ins:
;; http://wiki.audacityteam.org/wiki/Nyquist_Plug-ins_Reference
;control type "Fade Type" choice "Fade Up,Fade Down,S-Curve Up,S-Curve Down" 0
;control curve "Mid-fade Adjust (%)" real "" 0 -100 100
;control units "Start/End as" choice "% of Original,dB Gain" 0
;control gain-string-0 "Start (or end)" string "" "0" ""
;control gain-string-1 "End (or start)" string "" "100" ""
;control preset " Handy Presets\n(override controls)" choice "None Selected,Linear In,Linear Out,Exponential In,Exponential Out,Logarithmic In,Logarithmic Out,Rounded In,Rounded Out,Cosine In,Cosine Out,S-Curve In,S-Curve Out" 0
(setq err "")
; bad things may happen outside of the slider range.
(setq curve (min 1 (max -1 (/ curve 100.0))))
;;; Convert string to value
(defun string-to-val (string)
(setq val-array
(read (make-string-input-stream (format nil "(~a)" string))))
(if (and (= (length val-array) 1)
(numberp (car val-array)))
(let ((val (float (car val-array))))
(case units
(0 (/ val 100))
(t (db-to-linear val))))))
;;; invalid string error
(defun invalid-string (x y)
(unless x
(setf err (format nil "~aYou entered \"~a\"~%~
\"Start (or end):\" must be one number.~%"
err
gain-string-0)))
(unless y
(setf err (format nil "~aYou entered \"~a\"~%~
\"End (or start):\" must be one number.~%"
err gain-string-1)))
err)
;;; invalid values
(defun check-values (x y)
(when (or (< x 0)(< y 0))
(setf err (format nil "~a% values cannot be negative.~%" err))))
;;; select and apply fade
(defun fade (sig type curve g0 g1)
(mult sig
(case preset
(0 (case type ; Custom fade
(0 (simple (min g0 g1) (max g0 g1) curve))
(1 (simple (max g0 g1) (min g0 g1) curve))
(2 (raised-cos (min g0 g1)(max g0 g1) curve))
(T (raised-cos (max g0 g1) (min g0 g1) curve))))
(1 (linear 0 1)) ; Linear In
(2 (linear 1 0)) ; Linear Out
(3 (log-exp-curve -60 0)) ; Exponential In
(4 (log-exp-curve -60 1)) ; ExponentialOut
(5 (log-exp-curve 15.311 0)) ; Logarithmic In
(6 (log-exp-curve 15.311 1)) ; Logarithmic Out
(7 (simple-curve 0 1 0.5)) ; Rounded In
(8 (simple-curve 1 0 0.5)) ; Rounded Out
(9 (cosine-curve 0 1)) ; Cosine In
(10 (cosine-curve 1 0)) ; Cosine Out
(11 (raised-cos 0 1 0.0)) ; S-Curve In
(t (raised-cos 1 0 0.0))))) ; S-Curve Out
;;; Simple Curve:
;;; Use cosine for + values and linear for -ve.
(defun simple (g0 g1 curve)
(cond
((= g0 g1) g0) ; amplify
((and (> curve 0)(< curve 0.5)) ; +ve curve less than 0.5, lin to cosine
(let ((curve (* curve 2)))
(sim
(mult (- 1 curve)
(scale-curve g0 g1 (linear g0 g1))) ; linear
(mult curve
(scale-curve g0 g1 (cosine-curve g0 g1)))))) ; cosine curve
((> curve 0)
(cos-curve g0 g1 (- 1.5 curve))) ; +ve curve > 0.5
(t (simple-curve g0 g1 (- 1 (* 2 curve)))))) ; -ve curve
;;; linear fade to the power of pow
(defun simple-curve (g0 g1 pow)
(curve-adjust g0 g1 pow
(linear g0 g1)))
;;; cosine fade to the power of pow
(defun cos-curve (g0 g1 pow)
(curve-adjust g0 g1 pow
(cosine-curve g0 g1)))
(defun curve-adjust (g0 g1 pow env)
(scale-curve g0 g1
(if (= pow 1)
env
(snd-exp
(mult pow
(snd-log env))))))
;;; scale curves to min, max
(defun scale-curve (g0 g1 env)
(sum (min g0 g1)
(mult (abs (- g0 g1)) env)))
;;; cosine curve
(defun cosine-curve (g0 g1)
(let ((step (hz-to-step (/ 0.25 (get-duration 1))))
(phase (if (> g0 g1) 90 0)))
(osc step 1 *sine-table* phase)))
;;; linear fade in, out
(defun linear (g0 g1)
(control-srate-abs *sound-srate*
(if (> g0 g1) ; g0 = g1 does not occur here.
(pwlv 1 1 0) ; fade out
(pwlv 0 1 1)))) ; else fade in
;;; raised cosine fades
(defun raised-cos (g0 g1 curve)
(setq curve
(if (> curve 0)
(exp-scale-mid (* 2 curve)) ; mid-point -3dB @ Adjust = 50%
(exp-scale-mid (* 1.63 curve)))) ; mid-point -12dB @ Adjust = -50%
(setf env
(control-srate-abs *sound-srate* ; sound srate required for accuracy.
(cond
((= g0 g1) g0) ; amplify
((> g0 g1) ; fade down
(snd-exp
(mult (pwlv (- 1 curve) 1 1)
(snd-log (raised-cosin 90)))))
(t (snd-exp ; fade up
(mult (pwlv 1 1 (- 1 curve))
(snd-log (raised-cosin -90))))))))
(sum (min g0 g1)
(mult (abs (- g0 g1)) env)))
;;; raised cosine curve
(defun raised-cosin (phase)
(let ((hz (hz-to-step (/ (get-duration 2)))))
(mult 0.5
(sum 1
(osc hz 1 *sine-table* phase)))))
;;; log or exponential curve scaled 0 to 1
;;; x is the minimum level in dB before scaling
(defun log-exp-curve (x direction)
(control-srate-abs *sound-srate*
(let ((x (db-to-linear x)))
;; If direction=0 fade-in else fade-out
(if (= direction 0)
(setf env (pwev x 1 1))
(setf env (pwev 1 1 x)))
(mult (/ (- 1 x)) ; normalize to 0 dB
(diff env x))))) ; drop down to silence
;;; curve scaling for S-curve
(defun exp-scale-mid (x)
(let ((e (exp 1.0)))
(/ (- (exp (- 1 x)) e)
(- 1 e))))
(let ((gain0 (string-to-val gain-string-0))
(gain1 (string-to-val gain-string-1)))
(if (and gain0 gain1)
(check-values gain0 gain1)
(setf err (format nil "~a" (invalid-string gain0 gain1))))
(if (= (length err) 0)
(fade s type curve gain0 gain1)
(format nil "Error.~%~a." err)))
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