Add Limiter and Crossfade Clips effects.

plug-ins/crossfadeclips.ny

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+;nyquist plugin
+;version 4
+;type process
+;mergeclips 1
+;restoresplits 0
+;name "Crossfade Clips"
+;action "Crossfading..."
+;author "Steve Daulton"
+;copyright "Released under terms of the GNU General Public License version 2" 
+
+
+;; crossfadeclips.ny by Steve Daulton Dec 2014.
+;; Released under terms of the GNU General Public License version 2:
+;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+
+;; Instructions:
+;; Place two audio clips into the same track.
+;; Select (approximately) the same amount of audio from the
+;; end of one clip and the start of the other.
+;; Apply the effect.
+;; The selected regions will be crossfaded.
+;;
+;; Note, the audio clips do not need to be touching. Any
+;; white-space between the clips is ignored.
+;;
+;; If the selected region is continuous audio (no splits),
+;; the the first and last halves of the selected audio
+;; will be crossfaded.
+;;
+;; Advanced Tip:
+;; A discontinuity in a waveform may be smoothed by applying
+;; a short crossfade across the glitch.
+
+;; Limitations (should not occur in normal usage).
+;; 1) There may be no more than two clips selected in each channel.
+;; 2) The selection may not start or end in white-space.
+
+
+(setf err1 "Error.\nInvalid selection.\nMore than 2 audio clips selected.")
+(setf err2 "Error.\nInvalid selection.\nEmpty space at start/ end of the selection.")
+
+
+(defun find-ends (T0 T1 clips)
+"Look for a split or gap within the selection, or return the mid-point"
+  (let ((trk-ends ())    ;starts of clips
+        (trk-starts ())) ;ends of clips
+    (dolist (clip clips)
+      ;; look for clip enclosing the selection.
+      (when (and (>= (second clip) T1) (<= (first clip) T0))
+        (psetq trk-ends   (list (/ (+ T0 T1) 2))
+               trk-starts (list (/ (+ T0 T1) 2)))
+        (return))
+      ;; look for track starts.
+      (when (and (> (first clip) T0) (< (first clip) T1))
+        (push (first clip) trk-starts))
+      ;; look for track ends.
+      (when (and (> (second clip) T0) (< (second clip) T1))
+        (push (second clip) trk-ends))
+      ; stop looking when we have passed end of selection.
+      (when (> (first clip) T1) (return)))
+    ;; if exactly one split position for crossfading,
+    ;; return clip positions, else error.
+    (cond
+      ((and (= (length trk-ends) 1)
+            (= (length trk-starts) 1)
+            (<= (car trk-ends) (car trk-starts)))
+        (list (car trk-ends)(car trk-starts)))
+      ((or (> (length trk-ends) 1)
+           (> (length trk-starts) 1))
+        (throw 'error err1))
+      (T (throw 'error err2)))))
+
+(defun crossfade (sig out-end in-start end)
+"Do the crossfade"
+  (abs-env
+    (control-srate-abs *sound-srate*
+      (let* ((fade-out (mult sig (env out-end 0)))
+             (cflen (max out-end (- end in-start))) ;crossfade length
+             (finstart (max (- out-end (- end in-start)) 0))
+             (fade-in (mult (extract (- end cflen) end sig)
+                            (env (- cflen finstart) 1 finstart))))
+        (sim fade-out fade-in)))))
+
+(defun env (dur direction &optional (offset 0))
+"Generate envelope for crossfade"
+  (abs-env
+    (if (< dur 0.01)            ;make it linear
+        (control-srate-abs *sound-srate*
+          (if (= direction 0)
+              (pwlv 1 dur 0)      ;fade out
+              (pwlv 0 offset 0 (+ offset dur) 1)))  ;fade in
+        (if (= direction 0)     ;cosine curve
+            (cos-curve dur 0)
+            (seq (s-rest offset)
+                 (cos-curve dur 1))))))
+
+(defun cos-curve (dur direction)
+"Generate cosine curve"
+  (if (= direction 0) ;fade out
+      (osc (hz-to-step (/ 0.25 dur)) dur *sine-table* 90)
+      (osc (hz-to-step (/ 0.25 dur)) dur *sine-table* 0)))
+
+(defun process (sig t0 t1 clips)
+"Find the split positions and crossfade"
+  (setf fadeclips
+    (multichan-expand #'find-ends t0 t1 clips))
+  (if (arrayp fadeclips)
+      (prog ((fade-out-end (min (first (aref fadeclips 0))
+                                (first (aref fadeclips 1))))
+             (fade-in-start (max (second (aref fadeclips 0))
+                                 (second (aref fadeclips 1)))))
+        (return
+          (multichan-expand #'crossfade sig 
+                                       (- fade-out-end t0)
+                                       (- fade-in-start t0)
+                                       (- t1 t0))))
+      (crossfade sig
+                 (- (first fadeclips) t0)
+                 (- (second fadeclips) t0)
+                 (- t1 t0))))
+
+
+;;; Run the program.
+(if (= (length (get '*selection* 'tracks)) 1)
+    (catch 'error
+      (process *track*
+               (get '*selection* 'start) 
+               (get '*selection* 'end)
+               (get '*track* 'clips)))
+    "Error.\nCrossfade Clips may only be applied to one track.")