mirror of
https://github.com/CTCaer/RetroArch.git
synced 2024-12-22 10:49:02 +00:00
316 lines
9.2 KiB
C
316 lines
9.2 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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#include "../resampler.h"
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#include "../utils.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <complex.h>
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#include <string.h>
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#include <assert.h>
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#include <stdbool.h>
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static void gen_signal(float *out, double omega, double bias_samples, size_t samples)
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{
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for (size_t i = 0; i < samples; i += 2)
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{
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out[i + 0] = cos(((i >> 1) + bias_samples) * omega);
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out[i + 1] = out[i + 0];
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}
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}
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struct snr_result
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{
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double snr;
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double gain;
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unsigned alias_freq[3];
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double alias_power[3];
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};
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static unsigned bitrange(unsigned len)
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{
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unsigned ret = 0;
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while ((len >>= 1))
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ret++;
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return ret;
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}
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static unsigned bitswap(unsigned i, unsigned range)
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{
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unsigned ret = 0;
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for (unsigned shifts = 0; shifts < range; shifts++)
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ret |= i & (1 << (range - shifts - 1)) ? (1 << shifts) : 0;
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return ret;
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}
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// When interleaving the butterfly buffer, addressing puts bits in reverse.
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// [0, 1, 2, 3, 4, 5, 6, 7] => [0, 4, 2, 6, 1, 5, 3, 7]
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static void interleave(complex double *butterfly_buf, size_t samples)
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{
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unsigned range = bitrange(samples);
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for (unsigned i = 0; i < samples; i++)
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{
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unsigned target = bitswap(i, range);
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if (target > i)
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{
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complex double tmp = butterfly_buf[target];
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butterfly_buf[target] = butterfly_buf[i];
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butterfly_buf[i] = tmp;
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}
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}
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}
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static complex double gen_phase(double index)
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{
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return cexp(M_PI * I * index);
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}
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static void butterfly(complex double *a, complex double *b, complex double mod)
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{
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mod *= *b;
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complex double a_ = *a + mod;
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complex double b_ = *a - mod;
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*a = a_;
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*b = b_;
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}
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static void butterflies(complex double *butterfly_buf, double phase_dir, size_t step_size, size_t samples)
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{
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for (unsigned i = 0; i < samples; i += 2 * step_size)
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for (unsigned j = i; j < i + step_size; j++)
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butterfly(&butterfly_buf[j], &butterfly_buf[j + step_size], gen_phase((phase_dir * (j - i)) / step_size));
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}
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static void calculate_fft(const float *data, complex double *butterfly_buf, size_t samples)
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{
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// Enforce POT.
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assert((samples & (samples - 1)) == 0);
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for (unsigned i = 0; i < samples; i++)
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butterfly_buf[i] = data[2 * i];
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// Interleave buffer to work with FFT.
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interleave(butterfly_buf, samples);
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// Fly, lovely butterflies! :D
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for (unsigned step_size = 1; step_size < samples; step_size *= 2)
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butterflies(butterfly_buf, -1.0, step_size, samples);
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}
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static void calculate_fft_adjust(complex double *butterfly_buf, double gain, bool merge_high, size_t samples)
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{
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if (merge_high)
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{
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for (unsigned i = 1; i < samples / 2; i++)
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butterfly_buf[i] *= 2.0;
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}
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// Normalize amplitudes.
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for (unsigned i = 0; i < samples; i++)
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butterfly_buf[i] *= gain;
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}
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static void calculate_ifft(complex double *butterfly_buf, size_t samples, bool normalize)
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{
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// Enforce POT.
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assert((samples & (samples - 1)) == 0);
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interleave(butterfly_buf, samples);
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// Fly, lovely butterflies! In opposite direction! :D
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for (unsigned step_size = 1; step_size < samples; step_size *= 2)
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butterflies(butterfly_buf, 1.0, step_size, samples);
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if (normalize)
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calculate_fft_adjust(butterfly_buf, 1.0 / samples, false, samples);
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}
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static void test_fft(void)
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{
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fprintf(stderr, "Sanity checking FFT ...\n");
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float signal[32];
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complex double butterfly_buf[16];
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complex double buf_tmp[16];
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const float cos_freqs[] = {
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1.0, 4.0, 6.0,
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};
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const float sin_freqs[] = {
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-2.0, 5.0, 7.0,
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};
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for (unsigned i = 0; i < 16; i++)
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{
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signal[2 * i] = 0.0;
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for (unsigned j = 0; j < sizeof(cos_freqs) / sizeof(cos_freqs[0]); j++)
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signal[2 * i] += cos(2.0 * M_PI * i * cos_freqs[j] / 16.0);
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for (unsigned j = 0; j < sizeof(sin_freqs) / sizeof(sin_freqs[0]); j++)
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signal[2 * i] += sin(2.0 * M_PI * i * sin_freqs[j] / 16.0);
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}
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calculate_fft(signal, butterfly_buf, 16);
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memcpy(buf_tmp, butterfly_buf, sizeof(buf_tmp));
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calculate_fft_adjust(buf_tmp, 1.0 / 16, true, 16);
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fprintf(stderr, "FFT: { ");
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for (unsigned i = 0; i < 7; i++)
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fprintf(stderr, "(%4.2lf, %4.2lf), ", creal(buf_tmp[i]), cimag(buf_tmp[i]));
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fprintf(stderr, "(%4.2lf, %4.2lf) }\n", creal(buf_tmp[7]), cimag(buf_tmp[7]));
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calculate_ifft(butterfly_buf, 16, true);
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fprintf(stderr, "Original: { ");
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for (unsigned i = 0; i < 15; i++)
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fprintf(stderr, "%5.2f, ", signal[2 * i]);
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fprintf(stderr, "%5.2f }\n", signal[2 * 15]);
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fprintf(stderr, "FFT => IFFT: { ");
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for (unsigned i = 0; i < 15; i++)
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fprintf(stderr, "%5.2lf, ", creal(butterfly_buf[i]));
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fprintf(stderr, "%5.2lf }\n", creal(butterfly_buf[15]));
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}
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static void set_alias_power(struct snr_result *res, unsigned freq, double power)
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{
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for (unsigned i = 0; i < 3; i++)
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{
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if (power >= res->alias_power[i])
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{
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memmove(res->alias_freq + i + 1, res->alias_freq + i, (2 - i) * sizeof(res->alias_freq[0]));
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memmove(res->alias_power + i + 1, res->alias_power + i, (2 - i) * sizeof(res->alias_power[0]));
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res->alias_power[i] = power;
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res->alias_freq[i] = freq;
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break;
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}
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}
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}
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static void calculate_snr(struct snr_result *res,
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unsigned in_rate, unsigned max_rate,
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const float *resamp, complex double *butterfly_buf, size_t samples)
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{
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samples >>= 1;
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calculate_fft(resamp, butterfly_buf, samples);
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calculate_fft_adjust(butterfly_buf, 1.0 / samples, true, samples);
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memset(res, 0, sizeof(*res));
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double signal = cabs(butterfly_buf[in_rate] * butterfly_buf[in_rate]);
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butterfly_buf[in_rate] = 0.0;
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double noise = 0.0;
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// Aliased frequencies above half the original sampling rate are not considered.
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for (unsigned i = 0; i <= max_rate; i++)
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{
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double power = cabs(butterfly_buf[i] * butterfly_buf[i]);
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set_alias_power(res, i, power);
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noise += power;
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}
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res->snr = 10.0 * log10(signal / noise);
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res->gain = 10.0 * log10(signal);
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for (unsigned i = 0; i < 3; i++)
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res->alias_power[i] = 10.0 * log10(res->alias_power[i]);
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}
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int main(int argc, char *argv[])
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{
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if (argc != 2)
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{
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fprintf(stderr, "Usage: %s <ratio> (out-rate is fixed for FFT).\n", argv[0]);
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return 1;
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}
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double ratio = strtod(argv[1], NULL);
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const unsigned fft_samples = 1024 * 128;
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unsigned out_rate = fft_samples / 2;
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unsigned in_rate = out_rate / ratio;
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ratio = (double)out_rate / in_rate;
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if (ratio <= 1.0)
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{
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fprintf(stderr, "Ratio too low ...\n");
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return 1;
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}
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static const float freq_list[] = {
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0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009,
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0.010, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, 0.050,
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0.060, 0.070, 0.080, 0.090,
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0.10, 0.15, 0.20, 0.25, 0.30, 0.35,
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0.40, 0.41, 0.42, 0.43, 0.44, 0.45,
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0.46, 0.47, 0.48, 0.49,
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0.495, 0.496, 0.497, 0.498, 0.499,
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};
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unsigned samples = in_rate * 4;
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float *input = calloc(sizeof(float), samples);
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float *output = calloc(sizeof(float), (fft_samples + 1) * 2);
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complex double *butterfly_buf = calloc(sizeof(complex double), fft_samples / 2);
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assert(input);
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assert(output);
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rarch_resampler_t *re = resampler_new();
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assert(re);
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test_fft();
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printf("Omega,SNR,Gain\n");
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for (unsigned i = 0; i < sizeof(freq_list) / sizeof(freq_list[0]); i++)
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{
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unsigned freq = freq_list[i] * in_rate;
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double omega = 2.0 * M_PI * freq / in_rate;
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gen_signal(input, omega, 0, samples);
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struct resampler_data data = {
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.data_in = input,
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.data_out = output,
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.input_frames = in_rate * 2,
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.ratio = ratio,
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};
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resampler_process(re, &data);
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unsigned out_samples = data.output_frames * 2;
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assert(out_samples >= fft_samples * 2);
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// We generate 2 seconds worth of audio, however, only the last second is considered so phase has stabilized.
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struct snr_result res;
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calculate_snr(&res, freq, in_rate / 2, output + fft_samples, butterfly_buf, fft_samples);
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printf("SNR @ w = %5.3f : %6.2lf dB, Gain: %6.1lf dB\n",
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freq_list[i], res.snr, res.gain);
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printf("\tAliases: #1 (w = %5.3f, %6.2lf dB), #2 (w = %5.3f, %6.2lf dB), #3 (w = %5.3f, %6.2lf dB)\n",
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res.alias_freq[0] / (float)in_rate, res.alias_power[0],
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res.alias_freq[1] / (float)in_rate, res.alias_power[1],
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res.alias_freq[2] / (float)in_rate, res.alias_power[2]);
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}
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resampler_free(re);
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free(input);
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free(output);
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free(butterfly_buf);
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}
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