153 lines
4.3 KiB
C++
153 lines
4.3 KiB
C++
/*
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Copyright (C) 2012 Paul Davis
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#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 = 0;
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if (_speed != _target_speed) {
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acceleration = _target_speed - _speed;
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}
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for (framecnt_t outsample = 0; outsample < nframes; ++outsample) {
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double const d = phase[channel] + outsample * (_speed + acceleration);
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i = floor(d);
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Sample fractional_phase_part = d - 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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}
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double const distance = phase[channel] + nframes * (_speed + acceleration);
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i = floor(distance);
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phase[channel] = distance - i;
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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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i = floor(distance);
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phase[channel] = distance - floor(distance);
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} else {
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/* used to calculate play-distance with acceleration (silent roll)
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* (use same algorithm as real playback for identical rounding/floor'ing)
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*/
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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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i = floor(distance);
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}
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return i;
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}
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