+ /* 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];
+ }
+
+ 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);
+ }