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111 lines
3.0 KiB
C
111 lines
3.0 KiB
C
/* SSNES - A Super Nintendo Entertainment System (SNES) Emulator frontend for libsnes.
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* Copyright (C) 2010-2011 - Hans-Kristian Arntzen
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*
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* Some code herein may be based on code found in BSNES.
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*
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* SSNES 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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* SSNES 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 SSNES.
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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 "hermite.h"
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#include <stdlib.h>
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#define MAX_CHANS 8
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struct hermite_resampler
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{
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float chan_data[MAX_CHANS][4];
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double r_frac;
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unsigned chans;
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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) * 0.5;
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m1 = (d - b) * 0.5;
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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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hermite_resampler_t *hermite_new(unsigned channels)
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{
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if (channels > MAX_CHANS)
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return NULL;
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hermite_resampler_t *re = calloc(1, sizeof(*re));
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if (!re)
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return NULL;
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re->chans = channels;
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return re;
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}
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void hermite_process(hermite_resampler_t *re, struct hermite_data *data)
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{
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double r_step = 1.0 / data->src_ratio;
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size_t processed_out = 0;
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size_t processed_in = 0;
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size_t in_frames = data->input_frames;
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size_t out_frames = data->output_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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while (processed_in < in_frames && processed_out < out_frames)
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{
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while (re->r_frac <= 1.0 && processed_out < out_frames)
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{
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re->r_frac += r_step;
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for (unsigned i = 0; i < re->chans; i++)
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{
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float res = hermite_kernel(re->r_frac,
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re->chan_data[i][0], re->chan_data[i][1], re->chan_data[i][2], re->chan_data[i][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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if (re->r_frac >= 1.0)
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{
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re->r_frac -= 1.0;
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for (unsigned i = 0; i < re->chans; i++)
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{
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re->chan_data[i][0] = re->chan_data[i][1];
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re->chan_data[i][1] = re->chan_data[i][2];
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re->chan_data[i][2] = re->chan_data[i][3];
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re->chan_data[i][3] = *in_data++;
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}
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processed_in++;
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}
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}
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data->input_frames_used = processed_in;
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data->output_frames_gen = processed_out;
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}
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void hermite_free(hermite_resampler_t *re)
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{
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free(re);
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}
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