Symmetric x-fade, use equivalent of -6dB per step for 7 steps.

[ardour.git] / libs / ardour / interpolation.cc

diff --git a/libs/ardour/interpolation.cc b/libs/ardour/interpolation.cc
index ccaaca7e76322f13ff5097e6d1eeaaa0b203ecc4..bccaa45553484bb0eceb9e82eeb6b578a3b174a4 100644 (file)
--- a/libs/ardour/interpolation.cc
+++ b/libs/ardour/interpolation.cc
@@ -1,3 +1,22 @@
+/*
+    Copyright (C) 2012 Paul Davis 
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
 #include <stdint.h>
 #include <cstdio>
 
@@ -116,17 +135,18 @@ CubicInterpolation::interpolate (int channel, framecnt_t nframes, Sample *input,
                    inm1 = input[i];
            }
 
-    } else {
-
-           /* not sure that this is ever utilized - it implies that one of the input/output buffers is missing */
+           i = floor(distance);
+           phase[channel] = distance - floor(distance);
 
+    } else {
+           /* used to calculate play-distance with acceleration (silent roll)
+            * (use same algorithm as real playback for identical rounding/floor'ing)
+            */
            for (framecnt_t outsample = 0; outsample < nframes; ++outsample) {
                    distance += _speed + acceleration;
            }
+           i = floor(distance);
     }
 
-    i = floor(distance);
-    phase[channel] = distance - floor(distance);
-
     return i;
 }