David Robillard
62e730b57a
git-svn-id: svn://localhost/ardour2/branches/3.0@9288 d708f5d6-7413-0410-9779-e7cbd77b26cf
137 lines
3.5 KiB
C++
137 lines
3.5 KiB
C++
#include <stdint.h>
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#include <cstdio>
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#include "ardour/interpolation.h"
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using namespace ARDOUR;
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framecnt_t
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LinearInterpolation::interpolate (int channel, framecnt_t nframes, Sample *input, Sample *output)
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{
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// index in the input buffers
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framecnt_t i = 0;
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double acceleration;
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double distance = 0.0;
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if (_speed != _target_speed) {
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acceleration = _target_speed - _speed;
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} else {
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acceleration = 0.0;
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}
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distance = phase[channel];
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for (framecnt_t outsample = 0; outsample < nframes; ++outsample) {
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i = floor(distance);
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Sample fractional_phase_part = distance - i;
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if (fractional_phase_part >= 1.0) {
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fractional_phase_part -= 1.0;
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i++;
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}
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if (input && output) {
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// Linearly interpolate into the output buffer
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output[outsample] =
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input[i] * (1.0f - fractional_phase_part) +
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input[i+1] * fractional_phase_part;
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}
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distance += _speed + acceleration;
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}
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i = floor(distance);
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phase[channel] = distance - floor(distance);
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return i;
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}
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framecnt_t
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CubicInterpolation::interpolate (int channel, framecnt_t nframes, Sample *input, Sample *output)
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{
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// index in the input buffers
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framecnt_t i = 0;
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double acceleration;
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double distance = 0.0;
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if (_speed != _target_speed) {
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acceleration = _target_speed - _speed;
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} else {
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acceleration = 0.0;
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}
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distance = phase[channel];
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if (nframes < 3) {
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/* no interpolation possible */
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for (i = 0; i < nframes; ++i) {
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output[i] = input[i];
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}
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return nframes;
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}
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/* keep this condition out of the inner loop */
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if (input && output) {
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Sample inm1;
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if (floor (distance) == 0.0) {
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/* best guess for the fake point we have to add to be able to interpolate at i == 0:
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.... maintain slope of first actual segment ...
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*/
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inm1 = input[i] - (input[i+1] - input[i]);
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} else {
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inm1 = input[i-1];
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}
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for (framecnt_t outsample = 0; outsample < nframes; ++outsample) {
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float f = floor (distance);
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float fractional_phase_part = distance - f;
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/* get the index into the input we should start with */
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i = lrintf (f);
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/* fractional_phase_part only reaches 1.0 thanks to float imprecision. In theory
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it should always be < 1.0. If it ever >= 1.0, then bump the index we use
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and back it off. This is the point where we "skip" an entire sample in the
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input, because the phase part has accumulated so much error that we should
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really be closer to the next sample. or something like that ...
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*/
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if (fractional_phase_part >= 1.0) {
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fractional_phase_part -= 1.0;
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++i;
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}
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// Cubically interpolate into the output buffer: keep this inlined for speed and rely on compiler
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// optimization to take care of the rest
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// shamelessly ripped from Steve Harris' swh-plugins (ladspa-util.h)
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output[outsample] = input[i] + 0.5f * fractional_phase_part * (input[i+1] - inm1 +
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fractional_phase_part * (4.0f * input[i+1] + 2.0f * inm1 - 5.0f * input[i] - input[i+2] +
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fractional_phase_part * (3.0f * (input[i] - input[i+1]) - inm1 + input[i+2])));
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distance += _speed + acceleration;
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inm1 = input[i];
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}
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} else {
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/* not sure that this is ever utilized - it implies that one of the input/output buffers is missing */
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for (framecnt_t outsample = 0; outsample < nframes; ++outsample) {
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distance += _speed + acceleration;
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}
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}
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i = floor(distance);
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phase[channel] = distance - floor(distance);
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return i;
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}
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