137 lines
4.9 KiB
Common Lisp
137 lines
4.9 KiB
Common Lisp
$nyquist plugin
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$version 4
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$type process
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$mergeclips 1
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$restoresplits 0
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$name (_ "Crossfade Clips")
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$manpage "Crossfade_Clips"
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$action (_ "Crossfading...")
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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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;; crossfadeclips.ny by Steve Daulton Dec 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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;;
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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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;; Instructions:
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;; Place two audio clips into the same track.
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;; Select (approximately) the same amount of audio from the
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;; end of one clip and the start of the other.
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;; Apply the effect.
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;; The selected regions will be crossfaded.
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;;
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;; Note, the audio clips do not need to be touching. Any
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;; white-space between the clips is ignored.
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;;
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;; If the selected region is continuous audio (no splits),
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;; the the first and last halves of the selected audio
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;; will be crossfaded.
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;;
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;; Advanced Tip:
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;; A discontinuity in a waveform may be smoothed by applying
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;; a short crossfade across the glitch.
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;; Limitations (should not occur in normal usage).
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;; 1) There may be no more than two clips selected in each channel.
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;; 2) The selection may not start or end in white-space.
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(setf err1 (format nil (_ "Error.~%Invalid selection.~%More than 2 audio clips selected.")))
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(setf err2 (format nil (_ "Error.~%Invalid selection.~%Empty space at start/ end of the selection.")))
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(defun find-ends (T0 T1 clips)
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"Look for a split or gap within the selection, or return the mid-point"
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(let ((trk-ends ()) ;starts of clips
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(trk-starts ())) ;ends of clips
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(dolist (clip clips)
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;; look for clip enclosing the selection.
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(when (and (>= (second clip) T1) (<= (first clip) T0))
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(psetq trk-ends (list (/ (+ T0 T1) 2))
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trk-starts (list (/ (+ T0 T1) 2)))
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(return))
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;; look for track starts.
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(when (and (> (first clip) T0) (< (first clip) T1))
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(push (first clip) trk-starts))
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;; look for track ends.
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(when (and (> (second clip) T0) (< (second clip) T1))
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(push (second clip) trk-ends))
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; stop looking when we have passed end of selection.
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(when (> (first clip) T1) (return)))
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;; if exactly one split position for crossfading,
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;; return clip positions, else error.
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(cond
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((and (= (length trk-ends) 1)
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(= (length trk-starts) 1)
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(<= (car trk-ends) (car trk-starts)))
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(list (car trk-ends)(car trk-starts)))
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((or (> (length trk-ends) 1)
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(> (length trk-starts) 1))
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(throw 'error err1))
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(T (throw 'error err2)))))
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(defun crossfade (sig out-end in-start end)
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"Do the crossfade"
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(abs-env
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(control-srate-abs *sound-srate*
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(let* ((fade-out (mult sig (env out-end 0)))
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(cflen (max out-end (- end in-start))) ;crossfade length
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(finstart (max (- out-end (- end in-start)) 0))
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(fade-in (mult (extract (- end cflen) end sig)
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(env (- cflen finstart) 1 finstart))))
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(sim fade-out fade-in)))))
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(defun env (dur direction &optional (offset 0))
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"Generate envelope for crossfade"
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(abs-env
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(if (< dur 0.01) ;make it linear
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(control-srate-abs *sound-srate*
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(if (= direction 0)
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(pwlv 1 dur 0) ;fade out
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(pwlv 0 offset 0 (+ offset dur) 1))) ;fade in
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(if (= direction 0) ;cosine curve
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(cos-curve dur 0)
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(seq (s-rest offset)
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(cos-curve dur 1))))))
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(defun cos-curve (dur direction)
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"Generate cosine curve"
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(if (= direction 0) ;fade out
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(osc (hz-to-step (/ 0.25 dur)) dur *sine-table* 90)
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(osc (hz-to-step (/ 0.25 dur)) dur *sine-table* 0)))
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(defun process (sig t0 t1 clips)
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"Find the split positions and crossfade"
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(setf fadeclips
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(multichan-expand #'find-ends t0 t1 clips))
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(if (arrayp fadeclips)
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(prog ((fade-out-end (min (first (aref fadeclips 0))
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(first (aref fadeclips 1))))
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(fade-in-start (max (second (aref fadeclips 0))
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(second (aref fadeclips 1)))))
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(return
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(multichan-expand #'crossfade sig
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(- fade-out-end t0)
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(- fade-in-start t0)
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(- t1 t0))))
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(crossfade sig
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(- (first fadeclips) t0)
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(- (second fadeclips) t0)
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(- t1 t0))))
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;;; Run the program.
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(if (= (length (get '*selection* 'tracks)) 1)
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(catch 'error
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(process *track*
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(get '*selection* 'start)
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(get '*selection* 'end)
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(get '*track* 'clips)))
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(format nil (_ "Error.~%Crossfade Clips may only be applied to one track.")))
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