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_emphasis.c

79 lines
1.8 KiB

#include <stdio.h>
#include <stdint.h>
#include <math.h>
#include <string.h>
#include "../libsample/sample.h"
#include "../libfilter/iir_filter.h"
#include "../libemphasis/emphasis.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)
{
emphasis_t estate;
double cut_off = CUT_OFF_EMPHASIS_DEFAULT;
sample_t samples[SAMPLERATE];
double level;
double i;
init_emphasis(&estate, SAMPLERATE, cut_off, CUT_OFF_HIGHPASS_DEFAULT, CUT_OFF_LOWPASS_DEFAULT);
printf("testing pre-emphasis filter with cut-off frequency %.1f\n", cut_off);
for (i = 31.25; i < 4001; i = i * sqrt(sqrt(2.0))) {
gen_samples(samples, (double)i);
pre_emphasis(&estate, samples, SAMPLERATE);
level = get_level(samples);
printf("%s%.0f Hz: %.1f dB", debug_db(level), i, level2db(level));
if ((int)round(i) == 1000)
printf(" level=%.6f\n", level);
else
printf("\n");
}
printf("testing de-emphasis filter with cut-off frequency %.1f\n", cut_off);
for (i = 31.25; i < 4001; i = i * sqrt(sqrt(2.0))) {
gen_samples(samples, (double)i);
dc_filter(&estate, samples, SAMPLERATE);
de_emphasis(&estate, samples, SAMPLERATE);
level = get_level(samples);
printf("%s%.0f Hz: %.1f dB", debug_db(level), i, level2db(level));
if ((int)round(i) == 1000)
printf(" level=%.6f\n", level);
else
printf("\n");
}
return 0;
}