mirror of
https://github.com/libretro/RetroArch.git
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107 lines
2.7 KiB
C
107 lines
2.7 KiB
C
/* RetroArch - A frontend for libretro.
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* Copyright (C) 2010-2012 - Hans-Kristian Arntzen
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*
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* RetroArch is free software: you can redistribute it and/or modify it under the terms
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* of the GNU General Public License as published by the Free Software Found-
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* ation, either version 3 of the License, or (at your option) any later version.
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*
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* RetroArch is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
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* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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* PURPOSE. See the GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along with RetroArch.
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* If not, see <http://www.gnu.org/licenses/>.
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*/
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// Hermite resampler based on bsnes' audio library.
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#include "resampler.h"
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#include <stdlib.h>
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#include <math.h>
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#include "../boolean.h"
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#include "../general.h"
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#ifdef HAVE_CONFIG_H
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#include "../config.h"
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#endif
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#define CHANNELS 2
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struct rarch_resampler
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{
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float chan_data[CHANNELS][4];
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double r_frac;
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};
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static inline float hermite_kernel(float mu1, float a, float b, float c, float d)
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{
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float mu2, mu3, m0, m1, a0, a1, a2, a3;
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mu2 = mu1 * mu1;
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mu3 = mu2 * mu1;
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m0 = (c - a) * 0.5f;
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m1 = (d - b) * 0.5f;
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a0 = +2 * mu3 - 3 * mu2 + 1;
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a1 = mu3 - 2 * mu2 + mu1;
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a2 = mu3 - mu2;
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a3 = -2 * mu3 + 3 * mu2;
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return (a0 * b) + (a1 * m0) + (a2 * m1) + (a3 * c);
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}
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rarch_resampler_t *resampler_new(void)
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{
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RARCH_LOG("Hermite resampler [C]\n");
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return (rarch_resampler_t*)calloc(1, sizeof(rarch_resampler_t));
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}
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void resampler_process(rarch_resampler_t *re, struct resampler_data *data)
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{
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double r_step = 1.0 / data->ratio;
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size_t processed_out = 0;
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size_t in_frames = data->input_frames;
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const float *in_data = data->data_in;
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float *out_data = data->data_out;
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size_t i = 0;
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while (i < in_frames)
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{
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while (re->r_frac >= 1.0 && i < in_frames)
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{
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re->r_frac -= 1.0;
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for (unsigned c = 0; c < CHANNELS; c++)
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{
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re->chan_data[c][0] = re->chan_data[c][1];
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re->chan_data[c][1] = re->chan_data[c][2];
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re->chan_data[c][2] = re->chan_data[c][3];
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re->chan_data[c][3] = *in_data++;
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}
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i++;
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}
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while (re->r_frac <= 1.0)
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{
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re->r_frac += r_step;
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for (unsigned c = 0; c < CHANNELS; c++)
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{
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float res = hermite_kernel((float)re->r_frac,
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re->chan_data[c][0], re->chan_data[c][1],
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re->chan_data[c][2], re->chan_data[c][3]);
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*out_data++ = res;
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}
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processed_out++;
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}
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}
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data->output_frames = processed_out;
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}
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void resampler_free(rarch_resampler_t *re)
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{
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free(re);
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}
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