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https://github.com/libretro/RetroArch
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Improve SNR testing routines.
This commit is contained in:
Themaister
parent
5f330cbfa5
commit
cd54cc6822
@ -19,6 +19,7 @@
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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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#define CHANNELS 2
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@ -29,6 +30,18 @@ struct ssnes_resampler
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double r_frac;
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};
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void resampler_preinit(ssnes_resampler_t *re, double omega, unsigned *samples_offset)
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{
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*samples_offset = 4;
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for (unsigned i = 0; i < 4; i++)
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{
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re->chan_data[0][i] = cos(i * omega);
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re->chan_data[1][i] = re->chan_data[0][i];
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}
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re->r_frac = 0.0;
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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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@ -20,6 +20,12 @@
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#define __SSNES_RESAMPLER_H
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#include <stddef.h>
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#include <math.h>
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// M_PI is left out of ISO C99 :(
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#ifndef M_PI
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#define M_PI 3.14159265358979323846264338327
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#endif
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typedef struct ssnes_resampler ssnes_resampler_t;
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@ -38,5 +44,8 @@ ssnes_resampler_t *resampler_new(void);
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void resampler_process(ssnes_resampler_t *re, struct resampler_data *data);
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void resampler_free(ssnes_resampler_t *re);
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// Generate a starting cosine pulse with given frequency for testing (SNR, etc) purposes.
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void resampler_preinit(ssnes_resampler_t *re, double omega, unsigned *samples_offset);
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#endif
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17
audio/sinc.c
17
audio/sinc.c
@ -31,11 +31,6 @@
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#define SSNES_LOG(...)
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#endif
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// M_PI is left out of ISO C99 :(
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#ifndef M_PI
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#define M_PI 3.14159265358979323846264338327
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#endif
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#if __SSE__
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#include <xmmintrin.h>
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#endif
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@ -70,6 +65,18 @@ struct ssnes_resampler
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uint32_t time;
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};
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void resampler_preinit(ssnes_resampler_t *re, double omega, unsigned *samples_offset)
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{
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*samples_offset = SIDELOBES + 1;
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for (int i = 0; i < 2 * SIDELOBES; i++)
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{
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re->buffer_l[i] = cos((i - (SIDELOBES - 1)) * omega);
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re->buffer_r[i] = re->buffer_l[i];
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}
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re->time = 0;
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}
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static inline double sinc(double val)
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{
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if (fabs(val) < 0.00001)
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193
audio/test/snr.c
193
audio/test/snr.c
@ -22,96 +22,64 @@
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#include <math.h>
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#include <assert.h>
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static void gen_signal(float *out, double freq, double sample_rate, double bias_phase, size_t samples)
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static void gen_signal(float *out, double freq, double sample_rate, unsigned bias_samples, size_t samples)
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{
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double omega = 2.0 * M_PI * freq / sample_rate;
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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((2.0 * M_PI * freq * ((i >> 1) + bias_phase)) / sample_rate);
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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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static double calculate_snr(const float *orig, const float *resamp, size_t samples)
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static double calculate_gain(const float *orig, const float *resamp, size_t samples)
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{
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double orig_power = 0.0;
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double resamp_power = 0.0;
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for (size_t i = 0; i < samples; i += 2)
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orig_power += orig[i] * orig[i];
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for (size_t i = 0; i < samples; i += 2)
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resamp_power += resamp[i] * resamp[i];
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return sqrt(resamp_power / orig_power);
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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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};
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static void calculate_snr(struct snr_result *res, const float *orig, const float *resamp, size_t samples)
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{
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double noise = 0.0;
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double signal = 0.0;
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// Account for gain losses at higher frequencies as it's not really noise.
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double filter_gain = calculate_gain(orig, resamp, samples);
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double makeup_gain = 1.0 / filter_gain;
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for (size_t i = 0; i < samples; i += 2)
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signal += orig[i] * orig[i];
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for (size_t i = 0; i < samples; i += 2)
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{
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double diff = resamp[i] - orig[i];
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double diff = makeup_gain * resamp[i] - orig[i];
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noise += diff * diff;
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}
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double snr = 10 * log10(signal / noise);
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return snr;
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}
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#define SAMPLES 0x100000
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// This approach is kinda stupid.
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// There should be a good way to directly (and accurately) determine phase after correlating
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// the two signals.
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double find_best_snr(const float *output,
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size_t samples,
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double freq,
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double out_rate,
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uint64_t *first_offset, uint64_t *last_offset,
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uint64_t *first_subphase, uint64_t *last_subphase, uint64_t *subphases)
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{
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static float output_expected[SAMPLES];
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double max_snr = -100.0;
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uint64_t best_offset = *first_offset;
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uint64_t best_subphase = *first_subphase;
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for (uint64_t offset = *first_offset; offset <= *last_offset; offset += 2)
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{
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for (uint64_t subphase = *first_subphase; subphase <= *last_subphase; subphase++)
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{
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gen_signal(output_expected, freq, out_rate, (double)subphase / *subphases, samples);
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double snr = calculate_snr(output_expected, output + offset, samples);
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if (snr > max_snr)
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{
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max_snr = snr;
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best_offset = offset;
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best_subphase = subphase;
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}
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}
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}
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// Narrow down the search area.
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uint64_t left_offset = *first_offset;
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uint64_t right_offset = *last_offset;
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if (best_offset > left_offset)
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left_offset = best_offset - 1;
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if (best_offset < right_offset)
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right_offset = best_offset + 1;
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*first_offset = left_offset;
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*last_offset = right_offset;
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*subphases *= 2;
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best_subphase *= 2;
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uint64_t left_subphase = best_subphase - 2;
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uint64_t right_subphase = best_subphase + 2;
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if (best_subphase < 2)
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left_subphase = 0;
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*first_subphase = left_subphase;
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*last_subphase = right_subphase;
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return max_snr;
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res->snr = 10 * log10(signal / noise);
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res->gain = 20.0 * log10(filter_gain);
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}
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int main(int argc, char *argv[])
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{
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static float input[SAMPLES];
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static float output[SAMPLES * 8];
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float *input;
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float *output;
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float *output_expected;
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if (argc != 3)
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{
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@ -119,10 +87,10 @@ int main(int argc, char *argv[])
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return 1;
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}
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double in_rate = strtod(argv[1], NULL);
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double out_rate = strtod(argv[2], NULL);
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unsigned in_rate = strtoul(argv[1], NULL, 0);
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unsigned out_rate = strtoul(argv[2], NULL, 0);
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double ratio = out_rate / in_rate;
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double ratio = (double)out_rate / in_rate;
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if (ratio >= 7.99)
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{
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fprintf(stderr, "Ratio is too high ...\n");
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@ -136,47 +104,78 @@ int main(int argc, char *argv[])
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}
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static const float freq_list[] = {
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100, 200, 400, 600, 800, 1000,
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2000, 3000, 5000, 8000, 10000, 12000, 15000, 18000, 20000,
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30, 50,
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100, 150,
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200, 250,
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300, 350,
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400, 450,
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500, 550,
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600, 650,
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700, 800,
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900, 1000,
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1100, 1200,
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1300, 1500,
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1600, 1700,
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1800, 1900,
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2000, 2100,
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2200, 2300,
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2500, 3000,
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3500, 4000,
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4500, 5000,
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5500, 6000,
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6500, 7000,
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7500, 8000,
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9000, 9500,
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10000, 11000,
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12000, 13000,
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14000, 15000,
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16000, 17000,
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18000, 19000,
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20000, 21000,
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22000,
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};
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for (unsigned i = 0; i < sizeof(freq_list) / sizeof(freq_list[0]); i++)
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unsigned samples = in_rate * 2;
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input = calloc(sizeof(float), samples);
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output = calloc(sizeof(float), samples * 8);
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output_expected = calloc(sizeof(float), samples * 8);
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assert(input);
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assert(output);
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assert(output_expected);
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ssnes_resampler_t *re = resampler_new();
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assert(re);
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for (unsigned i = 0; i < sizeof(freq_list) / sizeof(freq_list[0]) && freq_list[i] < 0.5f * in_rate; i++)
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{
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gen_signal(input, freq_list[i], in_rate, 0.0, SAMPLES);
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double omega = 2.0 * M_PI * freq_list[i] / in_rate;
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unsigned sample_offset;
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resampler_preinit(re, omega, &sample_offset);
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gen_signal(input, freq_list[i], in_rate, sample_offset, 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 = SAMPLES / 2,
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.input_frames = in_rate,
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.ratio = ratio,
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};
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ssnes_resampler_t *re = resampler_new();
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assert(re);
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resampler_process(re, &data);
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resampler_free(re);
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#define MAX_OFFSET 128
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uint64_t first_offset = 0;
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uint64_t last_offset = MAX_OFFSET - 2;
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uint64_t first_subphase = 0;
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uint64_t last_subphase = 1;
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uint64_t subphases = 2;
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unsigned out_samples = data.output_frames * 2;
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gen_signal(output_expected, freq_list[i], out_rate, 0, out_samples);
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double max_snr = -100.0;
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struct snr_result res;
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calculate_snr(&res, output_expected, output, out_samples);
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// Iteratively find the correct SNR value.
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for (unsigned j = 0; j < 48; j++)
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{
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double snr = find_best_snr(output, SAMPLES - MAX_OFFSET, freq_list[i], out_rate,
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&first_offset, &last_offset,
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&first_subphase, &last_subphase, &subphases);
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if (snr > max_snr)
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max_snr = snr;
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}
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printf("SNR @ %.0f Hz: %lf dB\n", freq_list[i], max_snr);
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printf("SNR @ %7.1f Hz: %6.2lf dB, Gain: %6.1f dB\n",
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freq_list[i], res.snr, res.gain);
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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(output_expected);
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}
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