libs/ardour/interpolation.cc

   1 #include <stdint.h>
   2 #include <cstdio>
   3
   4 #include "ardour/interpolation.h"
   5
   6 using namespace ARDOUR;
   7
   8
   9 nframes_t
  10 LinearInterpolation::interpolate (int channel, nframes_t nframes, Sample *input, Sample *output)
  11 {
  12         // index in the input buffers
  13         nframes_t   i = 0;
  14
  15         double acceleration;
  16         double distance = 0.0;
  17
  18         if (_speed != _target_speed) {
  19                 acceleration = _target_speed - _speed;
  20         } else {
  21                 acceleration = 0.0;
  22         }
  23
  24         distance = phase[channel];
  25         for (nframes_t outsample = 0; outsample < nframes; ++outsample) {
  26                 i = floor(distance);
  27                 Sample fractional_phase_part = distance - i;
  28                 if (fractional_phase_part >= 1.0) {
  29                         fractional_phase_part -= 1.0;
  30                         i++;
  31                 }
  32
  33                 if (input && output) {
  34                 // Linearly interpolate into the output buffer
  35                         output[outsample] =
  36                                 input[i] * (1.0f - fractional_phase_part) +
  37                                 input[i+1] * fractional_phase_part;
  38                 }
  39                 distance += _speed + acceleration;
  40         }
  41
  42         i = floor(distance);
  43         phase[channel] = distance - floor(distance);
  44
  45         return i;
  46 }
  47
  48 nframes_t
  49 CubicInterpolation::interpolate (int channel, nframes_t nframes, Sample *input, Sample *output)
  50 {
  51     // index in the input buffers
  52     nframes_t   i = 0;
  53
  54     double acceleration;
  55     double distance = 0.0;
  56
  57     if (_speed != _target_speed) {
  58         acceleration = _target_speed - _speed;
  59     } else {
  60         acceleration = 0.0;
  61     }
  62
  63     distance = phase[channel];
  64     for (nframes_t outsample = 0; outsample < nframes; ++outsample) {
  65         i = floor(distance);
  66         Sample fractional_phase_part = distance - i;
  67         if (fractional_phase_part >= 1.0) {
  68             fractional_phase_part -= 1.0;
  69             i++;
  70         }
  71
  72         if (input && output) {
  73             // Cubically interpolate into the output buffer
  74             output[outsample] = cube_interp(fractional_phase_part, input[i-1], input[i], input[i+1], input[i+2]);
  75         }
  76         distance += _speed + acceleration;
  77     }
  78
  79     i = floor(distance);
  80     phase[channel] = distance - floor(distance);
  81
  82     return i;
  83 }