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Add hermite resampler.

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This commit is contained in:
Themaister 2011-02-06 12:57:12 +01:00
parent 93202f191c
commit 1b5e63f024
2 changed files with 139 additions and 0 deletions
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97
audio/hermite.c Normal file
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/* SSNES - A Super Nintendo Entertainment System (SNES) Emulator frontend for libsnes.
* Copyright (C) 2010-2011 - Hans-Kristian Arntzen
*
* Some code herein may be based on code found in BSNES.
*
* SSNES is free software: you can redistribute it and/or modify it under the terms
* of the GNU General Public License as published by the Free Software Found-
* ation, either version 3 of the License, or (at your option) any later version.
*
* SSNES is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
* PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along with SSNES.
* If not, see <http://www.gnu.org/licenses/>.
*/
// Hermite resampler based on bsnes' audio library.
#include "hermite.h"
#include <stdlib.h>
struct hermite_resampler
{
float chan_data[2][4];
double r_frac;
};
static inline float hermite_kernel(float mu1, float a, float b, float c, float d)
{
float mu2, mu3, m0, m1, a0, a1, a2, a3;
mu2 = mu1 * mu1;
mu3 = mu2 * mu1;
m0 = (c - a) * 0.5;
m1 = (d - b) * 0.5;
a0 = +2 * mu3 - 3 * mu2 + 1;
a1 = mu3 - 2 * mu2 + mu1;
a2 = mu3 - mu2;
a3 = -2 * mu3 + 3 * mu2;
return (a0 * b) + (a1 * m0) + (a2 * m1) + (a3 * c);
}
hermite_resampler_t *hermite_new(void)
{
hermite_resampler_t *re = calloc(1, sizeof(*re));
if (!re)
return NULL;
return re;
}
size_t hermite_process(hermite_resampler_t *re, const struct hermite_data *data)
{
double r_step = 1.0 / data->ratio;
size_t processed = 0;
size_t in_frames = data->in_frames;
const float *in_data = data->in_data;
float *out_data = data->out_data;
while (in_frames > 0)
{
while (re->r_frac <= 1.0)
{
re->r_frac += r_step;
for (unsigned i = 0; i < 2; i++)
{
float res = hermite_kernel(re->r_frac,
re->chan_data[i][0], re->chan_data[i][1], re->chan_data[i][2], re->chan_data[i][3]);
*out_data++ = res;
}
processed++;
}
re->r_frac -= 1.0;
for (unsigned i = 0; i < 2; i++)
{
re->chan_data[i][0] = re->chan_data[i][1];
re->chan_data[i][1] = re->chan_data[i][2];
re->chan_data[i][2] = re->chan_data[i][3];
re->chan_data[i][3] = *in_data++;
}
in_frames--;
}
return processed;
}
void hermite_free(hermite_resampler_t *re)
{
free(re);
}

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audio/hermite.h Normal file
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/* SSNES - A Super Nintendo Entertainment System (SNES) Emulator frontend for libsnes.
* Copyright (C) 2010-2011 - Hans-Kristian Arntzen
*
* Some code herein may be based on code found in BSNES.
*
* SSNES is free software: you can redistribute it and/or modify it under the terms
* of the GNU General Public License as published by the Free Software Found-
* ation, either version 3 of the License, or (at your option) any later version.
*
* SSNES is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
* PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along with SSNES.
* If not, see <http://www.gnu.org/licenses/>.
*/
// Hermite resampler based on bsnes' audio library.
#ifndef __SSNES_HERMITE_H
#define __SSNES_HERMITE_H
#include <stddef.h>
typedef struct hermite_resampler hermite_resampler_t;
hermite_resampler_t *hermite_new(void);
struct hermite_data
{
const float *in_data;
float *out_data; // We make it really simple and assume that there is always enough space. :)
size_t in_frames;
double ratio;
};
size_t hermite_process(hermite_resampler_t *re, const struct hermite_data *data);
void hermite_free(hermite_resampler_t *re);
#endif