mirror of
https://github.com/cookiengineer/audacity
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50 lines
1.7 KiB
Common Lisp
50 lines
1.7 KiB
Common Lisp
;nyquist plug-in
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;version 4
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;type process
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;name "Crossfade Tracks..."
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;action "Crossfading..."
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;preview disabled - cannot use preview because tracks are processed differently.
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;; crossfadetracks.ny by Steve Daulton Nov 2014.
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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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;control type "Fade type" choice "Constant Gain,Constant Power 1,Constant Power 2,Custom Curve" 0
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;control curve "Custom curve" real "" 0 0 1
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(defun crossfade (type)
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(mult *track*
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(cond
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((= (get '*track* 'index) 1) ; fade out.
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(case type
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(0 (pwlv 1 1 0))
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(1 (osc (hz-to-step (/ (get-duration 4))) 1 *sine-table* 90))
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(2 (s-sqrt (pwlv 1 1 0)))
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(T (custom curve 0))))
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(T ; else fade in.
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(setf *control-srate* *sound-srate*)
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(case type
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(0 (pwlv 0 1 1))
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(1 (osc (hz-to-step (/ (get-duration 4))) 1))
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(2 (s-sqrt (pwlv 0 1 1)))
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(T (custom curve 1)))))))
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(defun custom (curve inout)
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;; 'epsilon' defines the curvature of a logarithmc curve.
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;; To avoid log 0 or /0 it must be > 0 and < 1.
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(let* ((curve (+ 0.99 (* -0.98 (min 1 (max 0 curve)))))
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; magic number 2.7 gives approx 'constant power' curve at 50% setting.
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(epsilon (power curve 2.7)))
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(if (= inout 0)
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(setf logcurve (pwev epsilon 1 1))
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(setf logcurve (pwev 1 1 epsilon)))
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(sum 1
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(mult (/ -1 (- 1 epsilon))
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(diff logcurve epsilon)))))
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(let ((tracks (length (get '*selection* 'tracks))))
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(case tracks
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(1 "Only 1 track selected.\n'Crossfade Tracks' requires 2 tracks.")
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(2 (crossfade type))
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(T "Too many tracks selected.\n'Crossfade Tracks' requires 2 tracks.")))
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