mirror of
https://github.com/cookiengineer/audacity
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77 lines
2.8 KiB
Common Lisp
77 lines
2.8 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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;manpage "Crossfade_Tracks"
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;debugbutton disabled
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;action "Crossfading..."
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;preview selection
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;author "Steve Daulton"
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;copyright "Released under terms of the GNU General Public License version 2"
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;; crossfadetracks.ny by Steve Daulton Nov 2014 / Sep 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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;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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;control direction "Fade direction" choice "Automatic,Alternating Out / In,Alternating In / Out" 0
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(defun crossfade (type dir curve)
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(setf fade-out
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(case dir
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(0 (equal (guessdirection) 'OUT)) ; auto
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(1 (oddp (get '*track* 'index))) ; fade out odd
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(T (evenp (get '*track* 'index))))) ; fade out even
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(mult *track*
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(cond
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(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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; Control envelope sample rate must match sound so that lengths
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; match exactly, otherwise we get a click at the end of the fade.
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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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; Scale and invert curve for 0 to unity gain.
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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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(defun guessdirection ()
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"If the selection is closer to the start of the
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audio clip, fade in, otherwise fade out."
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(let* ((start (get '*selection* 'start))
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(end (get '*selection* 'end))
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(clips (get '*track* 'clips))
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(in-dist end)
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(out-dist end))
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(if (arrayp clips)
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(setf clips (append (aref clips 0)(aref clips 1))))
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(dotimes (i (length clips))
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(setf in-dist (min in-dist (abs (- start (first (nth i clips))))))
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(setf out-dist (min out-dist (abs (- end (second (nth i clips)))))))
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(if (< in-dist out-dist) 'in 'out)))
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(if (< (length (get '*selection* 'tracks)) 2)
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"Error.\nSelect 2 (or more) tracks to crossfade."
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(crossfade type direction curve))
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