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#include <stdint.h>
#include "ardour/interpolation.h"
using namespace ARDOUR;
nframes_t
LinearInterpolation::interpolate (nframes_t nframes, Sample *input, Sample *output)
{
// the idea is that when the speed is not 1.0, we have to
// interpolate between samples and then we have to store where we thought we were.
// rather than being at sample N or N+1, we were at N+0.8792922
// index in the input buffers
nframes_t i = 0;
double acceleration;
double distance = 0.0;
if (_speed != _target_speed) {
acceleration = _target_speed - _speed;
} else {
acceleration = 0.0;
}
for (nframes_t outsample = 0; outsample < nframes; ++outsample) {
i = distance;
Sample fractional_phase_part = distance - i;
if (input && output) {
// Linearly interpolate into the output buffer
output[outsample] =
input[i] * (1.0f - fractional_phase_part) +
input[i+1] * fractional_phase_part;
}
distance += _speed + acceleration;
}
i = (distance + 0.5L);
// playback distance
return i;
}
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