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#include <stdint.h>
#include <cstdio>
#include "ardour/interpolation.h"
using namespace ARDOUR;
framecnt_t
LinearInterpolation::interpolate (int channel, framecnt_t nframes, Sample *input, Sample *output)
{
// index in the input buffers
framecnt_t i = 0;
double acceleration = 0;
if (_speed != _target_speed) {
acceleration = _target_speed - _speed;
}
for (framecnt_t outsample = 0; outsample < nframes; ++outsample) {
double const d = phase[channel] + outsample * (_speed + acceleration);
i = floor(d);
Sample fractional_phase_part = d - i;
if (fractional_phase_part >= 1.0) {
fractional_phase_part -= 1.0;
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;
}
}
double const distance = phase[channel] + nframes * (_speed + acceleration);
i = floor(distance);
phase[channel] = distance - i;
return i;
}
framecnt_t
CubicInterpolation::interpolate (int channel, framecnt_t nframes, Sample *input, Sample *output)
{
// index in the input buffers
framecnt_t i = 0;
double acceleration;
double distance = 0.0;
if (_speed != _target_speed) {
acceleration = _target_speed - _speed;
} else {
acceleration = 0.0;
}
distance = phase[channel];
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);
phase[channel] = distance - floor(distance);
return i;
}
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