Util: Start bringing up better audio resampling

This commit is contained in:
Vicki Pfau 2024-04-10 23:54:40 -07:00
parent 72202544bb
commit cbd117eb3a
3 changed files with 117 additions and 0 deletions

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@ -0,0 +1,33 @@
/* Copyright (c) 2013-2024 Jeffrey Pfau
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef M_INTERPOLATOR_H
#define M_INTERPOLATOR_H
#include <mgba-util/common.h>
struct mSampleBuffer {
int16_t* data;
size_t samples;
int channels;
};
struct mInterpolator {
int16_t (*interpolate)(const struct mInterpolator* interp, const struct mSampleBuffer* data, double time, double sampleStep);
};
struct mInterpolatorSinc {
struct mInterpolator d;
unsigned resolution;
unsigned width;
double* sincLut;
double* windowLut;
};
void mInterpolatorSincInit(struct mInterpolatorSinc* interp, unsigned resolution, unsigned width);
void mInterpolatorSincDeinit(struct mInterpolatorSinc* interp);
#endif

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@ -19,6 +19,7 @@ set(SOURCE_FILES
image.c image.c
image/export.c image/export.c
image/png-io.c image/png-io.c
interpolator.c
patch.c patch.c
patch-fast.c patch-fast.c
patch-ips.c patch-ips.c

83
src/util/interpolator.c Normal file
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/* Copyright (c) 2013-2024 Jeffrey Pfau
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include <mgba-util/interpolator.h>
enum {
mSINC_RESOLUTION = 8192,
mSINC_WIDTH = 8,
};
static int16_t mInterpolatorSincInterpolate(const struct mInterpolator*, const struct mSampleBuffer* data, double time, double sampleStep);
void mInterpolatorSincInit(struct mInterpolatorSinc* interp, unsigned resolution, unsigned width) {
interp->d.interpolate = mInterpolatorSincInterpolate;
if (!resolution) {
resolution = mSINC_RESOLUTION;
}
if (!width) {
width = mSINC_WIDTH;
}
unsigned samples = resolution * width;
double dy = M_PI / samples;
double y = dy;
double dx = dy * width;
double x = dx;
interp->sincLut = calloc(samples + 1, sizeof(double));
interp->windowLut = calloc(samples + 1, sizeof(double));
interp->sincLut[0] = 0;
interp->windowLut[0] = 1;
unsigned i;
for (i = 1; i <= samples; ++i, x += dx, y += dy) {
interp->sincLut[i] = x < width ? sin(x) / x : 0.0;
// Three term Nuttall window with continuous first derivative
interp->windowLut[i] = 0.40897 + 0.5 * cos(y) + 0.09103 * cos(2 * y);
}
}
void mInterpolatorSincDeinit(struct mInterpolatorSinc* interp) {
free(interp->sincLut);
free(interp->windowLut);
}
int16_t mInterpolatorSincInterpolate(const struct mInterpolator* interpolator, const struct mSampleBuffer* data, double time, double sampleStep) {
struct mInterpolatorSinc* interp = (struct mInterpolatorSinc*) interpolator;
ssize_t index = (ssize_t) time;
double subsample = time - floor(time);
unsigned step = sampleStep > 1 ? interp->resolution * sampleStep : interp->resolution;
unsigned yShift = subsample * step;
unsigned xShift = subsample * interp->resolution;
double sum = 0.0;
double kernelSum = 0.0;
double kernel;
ssize_t i;
for (i = 1 - (ssize_t) interp->width; i <= (ssize_t) interp->width; ++i) {
unsigned window = i * interp->resolution;
if (yShift > window) {
window = yShift - window;
} else {
window -= yShift;
}
unsigned sinc = i * step;
if (xShift > sinc) {
sinc = xShift - sinc;
} else {
sinc -= xShift;
}
kernel = interp->sincLut[sinc] * interp->windowLut[window];
kernelSum += kernel;
if (index + i >= 0 && index + i < (ssize_t) data->samples) {
sum += data->data[(index + i) * data->channels] * kernel;
}
}
return sum / kernelSum;
}