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$nyquist plug-in
$version 4
$type process
$name (_ "Crossfade Tracks")
$manpage "Crossfade_Tracks"
$debugbutton disabled
$action (_ "Crossfading...")
$preview selection
$author (_ "Steve Daulton")
$release 3.0.4
$copyright (_ "GNU General Public License v2.0 or later")
;; crossfadetracks.ny by Steve Daulton Nov 2014 / Sep 2015
;; Released under terms of the GNU General Public License v2.0 or later:
;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;;
;; For information about writing and modifying Nyquist plug-ins:
;; https://wiki.audacityteam.org/wiki/Nyquist_Plug-ins_Reference
$control type (_ "Fade type") choice (
("ConstantGain" (_ "Constant Gain"))
("ConstantPower1" (_ "Constant Power 1"))
("ConstantPower2" (_ "Constant Power 2"))
("CustomCurve" (_ "Custom Curve"))
) 0
$control curve (_ "Custom curve") real "" 0 0 1
$control direction (_ "Fade direction") choice (
(_ "Automatic")
("OutIn" (_ "Alternating Out / In"))
("InOut" (_ "Alternating In / Out"))
) 0
(defun crossfade (type dir curve)
(setf fade-out
(case dir
(0 (equal (guessdirection) 'OUT)) ; auto
(1 (oddp (get '*track* 'index))) ; fade out odd
(T (evenp (get '*track* 'index))))) ; fade out even
; Set control rate to sound rate to ensure length is exact.
(setf *control-srate* *sound-srate*)
(mult *track*
(cond
(fade-out
(case type
(0 (pwlv 1 1 0))
(1 (osc (hz-to-step (/ (get-duration 4))) 1 *sine-table* 90))
(2 (s-sqrt (pwlv 1 1 0)))
(T (custom curve 0))))
(T ; else fade in.
(case type
(0 (pwlv 0 1 1))
(1 (osc (hz-to-step (/ (get-duration 4))) 1))
(2 (s-sqrt (pwlv 0 1 1)))
(T (custom curve 1)))))))
(defun custom (curve inout)
;; 'epsilon' defines the curvature of a logarithmc curve.
;; To avoid log 0 or /0 it must be > 0 and < 1.
(let* ((curve (+ 0.99 (* -0.98 (min 1 (max 0 curve)))))
; magic number 2.7 gives approx 'constant power' curve at 50% setting.
(epsilon (power curve 2.7)))
(if (= inout 0)
(setf logcurve (pwev epsilon 1 1))
(setf logcurve (pwev 1 1 epsilon)))
; Scale and invert curve for 0 to unity gain.
(sum 1
(mult (/ -1 (- 1 epsilon))
(diff logcurve epsilon)))))
(defun guessdirection ()
"If the selection is closer to the start of the
audio clip, fade in, otherwise fade out."
(let* ((start (get '*selection* 'start))
(end (get '*selection* 'end))
(clips (get '*track* 'clips))
(in-dist end)
(out-dist end))
(if (arrayp clips)
(setf clips (append (aref clips 0)(aref clips 1))))
(dotimes (i (length clips))
(setf in-dist (min in-dist (abs (- start (first (nth i clips))))))
(setf out-dist (min out-dist (abs (- end (second (nth i clips)))))))
(if (< in-dist out-dist) 'in 'out)))
(if (< (length (get '*selection* 'tracks)) 2)
(format nil (_ "Error.~%Select 2 (or more) tracks to crossfade."))
(crossfade type direction curve))