get Delivery to disconnect from any signals it is connected to relatively early in...

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

diff --git a/libs/ardour/interpolation.cc b/libs/ardour/interpolation.cc
index 79ec82b482099ee6c801b18ffa6c59bf99196b43..20ab584885e7f19dd6bd348c2648b5d429c08c1b 100644 (file)
--- a/libs/ardour/interpolation.cc
+++ b/libs/ardour/interpolation.cc
@@ -6,11 +6,11 @@
 using namespace ARDOUR;
 
 
-nframes_t
-LinearInterpolation::interpolate (int channel, nframes_t nframes, Sample *input, Sample *output)
+framecnt_t
+LinearInterpolation::interpolate (int channel, framecnt_t nframes, Sample *input, Sample *output)
 {
        // index in the input buffers
-       nframes_t   i = 0;
+       framecnt_t   i = 0;
 
        double acceleration;
        double distance = 0.0;
@@ -22,7 +22,7 @@ LinearInterpolation::interpolate (int channel, nframes_t nframes, Sample *input,
        }
 
        distance = phase[channel];
-       for (nframes_t outsample = 0; outsample < nframes; ++outsample) {
+       for (framecnt_t outsample = 0; outsample < nframes; ++outsample) {
                i = floor(distance);
                Sample fractional_phase_part = distance - i;
                if (fractional_phase_part >= 1.0) {
@@ -45,11 +45,11 @@ LinearInterpolation::interpolate (int channel, nframes_t nframes, Sample *input,
        return i;
 }
 
-nframes_t
-CubicInterpolation::interpolate (int channel, nframes_t nframes, Sample *input, Sample *output)
+framecnt_t
+CubicInterpolation::interpolate (int channel, framecnt_t nframes, Sample *input, Sample *output)
 {
     // index in the input buffers
-    nframes_t   i = 0;
+    framecnt_t   i = 0;
 
     double acceleration;
     double distance = 0.0;
@@ -57,23 +57,76 @@ CubicInterpolation::interpolate (int channel, nframes_t nframes, Sample *input,
     if (_speed != _target_speed) {
         acceleration = _target_speed - _speed;
     } else {
-        acceleration = 0.0;
+           acceleration = 0.0;
     }
 
     distance = phase[channel];
-    for (nframes_t outsample = 0; outsample < nframes; ++outsample) {
-        i = floor(distance);
-        Sample fractional_phase_part = distance - i;
-        if (fractional_phase_part >= 1.0) {
-            fractional_phase_part -= 1.0;
-            i++;
-        }
-
-        if (input && output) {
-            // Cubically interpolate into the output buffer
-            output[outsample] = cube_interp(fractional_phase_part, input[i-1], input[i], input[i+1], input[i+2]);
-        }
-        distance += _speed + acceleration;
+
+    if (nframes < 3) {
+           /* no interpolation possible */
+
+           for (i = 0; i < nframes; ++i) {
+                   output[i] = input[i];
+           }
+
+           return nframes;
+    }
+
+    /* keep this condition out of the inner loop */
+
+    if (input && output) {
+
+           Sample inm1;
+
+           if (floor (distance) == 0.0) {
+                   /* best guess for the fake point we have to add to be able to interpolate at i == 0:
+                      .... maintain slope of first actual segment ...
+                   */
+                   inm1 = input[i] - (input[i+1] - input[i]);
+           } else {
+                   inm1 = input[i-1];
+           }
+
+           for (framecnt_t outsample = 0; outsample < nframes; ++outsample) {
+
+                   float f = floor (distance);
+                   float fractional_phase_part = distance - f;
+
+                   /* get the index into the input we should start with */
+
+                   i = lrintf (f);
+
+                   /* fractional_phase_part only reaches 1.0 thanks to float imprecision. In theory
+                      it should always be < 1.0. If it ever >= 1.0, then bump the index we use
+                      and back it off. This is the point where we "skip" an entire sample in the
+                      input, because the phase part has accumulated so much error that we should
+                      really be closer to the next sample. or something like that ...
+                   */
+
+                   if (fractional_phase_part >= 1.0) {
+                           fractional_phase_part -= 1.0;
+                           ++i;
+                   }
+
+                   // Cubically interpolate into the output buffer: keep this inlined for speed and rely on compiler
+                   // optimization to take care of the rest
+                   // shamelessly ripped from Steve Harris' swh-plugins (ladspa-util.h)
+
+                   output[outsample] = input[i] + 0.5f * fractional_phase_part * (input[i+1] - inm1 +
+                                                         fractional_phase_part * (4.0f * input[i+1] + 2.0f * inm1 - 5.0f * input[i] - input[i+2] +
+                                                               fractional_phase_part * (3.0f * (input[i] - input[i+1]) - inm1 + input[i+2])));
+
+                   distance += _speed + acceleration;
+                   inm1 = input[i];
+           }
+
+    } else {
+
+           /* not sure that this is ever utilized - it implies that one of the input/output buffers is missing */
+
+           for (framecnt_t outsample = 0; outsample < nframes; ++outsample) {
+                   distance += _speed + acceleration;
+           }
     }
 
     i = floor(distance);