New Nyquist crossfade effect added.

plug-ins/crossfadetracks.ny

@@ -0,0 +1,49 @@
+;nyquist plug-in
+;version 4
+;type process
+;name "Crossfade Tracks..."
+;action "Crossfading..."
+;preview disabled - cannot use preview because tracks are processed differently.
+
+;; crossfadetracks.ny by Steve Daulton Nov 2014.
+;; Released under terms of the GNU General Public License version 2:
+;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html .
+
+;control type "Fade type" choice "Constant Gain,Constant Power 1,Constant Power 2,Custom Curve" 0
+;control curve "Custom curve" real "" 0 0 1
+
+(defun crossfade (type)
+  (mult *track*
+    (cond
+      ((= (get '*track* 'index) 1)  ; 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.
+        (setf *control-srate* *sound-srate*)
+        (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)))
+    (sum 1
+         (mult (/ -1 (- 1 epsilon))
+               (diff logcurve epsilon)))))
+
+(let ((tracks (get '*selection* 'tracks)))
+  (case tracks
+    (1 "Only 1 track selected.\n'Crossfade Tracks' requires 2 tracks.")
+    (2 (crossfade type))
+    (T "Too many tracks selected.\n'Crossfade Tracks' requires 2 tracks.")))