An implementation of Analog cellular networks like A-Netz, B-Netz, C-Netz, NMT, AMPS, TACS, JTACS, Radiocom 2000, IMTS, MPT1327, Eurosignal and more http://osmocom-analog.eversberg.eu/
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osmocom-analog/src/test/test_filter.c

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3.6 KiB

#include <stdio.h>
#include <stdint.h>
#include <math.h>
#include <string.h>
#include "../libsample/sample.h"
#include "../libfilter/iir_filter.h"
#include "../libfilter/fir_filter.h"
#include "../libdebug/debug.h"
#define level2db(level) (20 * log10(level))
#define db2level(db) pow(10, (double)db / 20.0)
#define SAMPLERATE 48000
static double get_level(sample_t *samples)
{
int i;
double envelope = 0;
for (i = SAMPLERATE/2; i < SAMPLERATE; i++) {
if (samples[i] > envelope)
envelope = samples[i];
}
return envelope;
}
static void gen_samples(sample_t *samples, double freq)
{
int i;
double value;
for (i = 0; i < SAMPLERATE; i++) {
value = cos(2.0 * M_PI * freq / (double)SAMPLERATE * (double)i);
samples[i] = value;
}
}
int num_kanal;
int main(void)
{
iir_filter_t filter_low;
iir_filter_t filter_high;
fir_filter_t *fir_low/*, *fir_high*/;
sample_t samples[SAMPLERATE];
double level;
int iter = 2;
int i;
printf("testing low-pass filter with %d iterations\n", iter);
iir_lowpass_init(&filter_low, 1000.0, SAMPLERATE, iter);
for (i = 0; i < 4001; i += 100) {
gen_samples(samples, (double)i);
iir_process(&filter_low, samples, SAMPLERATE);
level = get_level(samples);
printf("%s%4d Hz: %.1f dB", debug_db(level), i, level2db(level));
if (i == 1000)
printf(" cutoff\n");
else if (i == 2000)
printf(" double frequency\n");
else if (i == 4000)
printf(" quad frequency\n");
else
printf("\n");
}
printf("testing high-pass filter with %d iterations\n", iter);
iir_highpass_init(&filter_high, 2000.0, SAMPLERATE, iter);
for (i = 0; i < 4001; i += 100) {
gen_samples(samples, (double)i);
iir_process(&filter_high, samples, SAMPLERATE);
level = get_level(samples);
printf("%s%4d Hz: %.1f dB", debug_db(level), i, level2db(level));
if (i == 2000)
printf(" cutoff\n");
else if (i == 1000)
printf(" half frequency\n");
else if (i == 500)
printf(" quarter frequency\n");
else
printf("\n");
}
printf("testing band-pass filter with %d iterations\n", iter);
iir_lowpass_init(&filter_low, 2000.0, SAMPLERATE, iter);
iir_highpass_init(&filter_high, 1000.0, SAMPLERATE, iter);
for (i = 0; i < 4001; i += 100) {
gen_samples(samples, (double)i);
iir_process(&filter_low, samples, SAMPLERATE);
iir_process(&filter_high, samples, SAMPLERATE);
level = get_level(samples);
printf("%s%4d Hz: %.1f dB", debug_db(level), i, level2db(level));
if (i == 1000)
printf(" cutoff high\n");
else if (i == 2000)
printf(" cutoff low\n");
else
printf("\n");
}
double freq = 2000.0;
double tb = 400.0;
printf("testing low-pass FIR filter with %.0fHz transition bandwidth\n", tb);
fir_low = fir_lowpass_init(SAMPLERATE, freq, tb);
printf("Using %d taps\n", fir_low->ntaps);
for (i = 0; i < 4001; i += 100) {
gen_samples(samples, (double)i);
fir_process(fir_low, samples, SAMPLERATE);
level = get_level(samples);
printf("%s%s%4d Hz: %.1f dB", debug_amplitude(level), debug_db(level), i, level2db(level));
if (i == freq)
printf(" cutoff\n");
else
printf("\n");
}
fir_exit(fir_low);
#if 0
double freq1 = 1000.0, freq2 = 2000.0;
tb = 100.0;
printf("testing two-pass FIR filter\n");
fir_high = fir_twopass_init(SAMPLERATE, freq1, freq2, tb);
printf("Using %d taps\n", fir_high->ntaps);
for (i = 0; i < 4001; i += 100) {
gen_samples(samples, (double)i);
fir_process(fir_high, samples, SAMPLERATE);
level = get_level(samples);
printf("%s%s%4d Hz: %.1f dB", debug_amplitude(level), debug_db(level), i, level2db(level));
if (i == freq1 || i == freq2)
printf(" cutoff\n");
else
printf("\n");
}
fir_exit(fir_high);
#endif
return 0;
}