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_compandor.c

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3.9 KiB

#include <stdio.h>
#include <stdint.h>
#include <math.h>
#include <string.h>
#include "../libsample/sample.h"
#include "../libcompandor/compandor.h"
#define level2db(level) (20 * log10(level))
#define db2level(db) pow(10, (double)db / 20.0)
#define SAMPLERATE 48000
#define ATTACK_MS 15.0
#define RECOVERY_MS 15.0
static double test_frequency[3] = { 2000.0, 4000.0, 1000.0 };
static sample_t samples_4db[SAMPLERATE];
static sample_t samples_16db[SAMPLERATE];
static sample_t samples_2db[SAMPLERATE];
static sample_t samples_8db[SAMPLERATE];
static sample_t samples_0db[SAMPLERATE];
/* generate 2 samples: one with -4 dB, the other with -16 dB */
static void generate_test_sample(double test_frequency)
{
int i;
double value;
for (i = 0; i < SAMPLERATE; i++) {
value = cos(2.0 * M_PI * test_frequency / (double)SAMPLERATE * i);
samples_4db[i] = value * db2level(-4);
samples_16db[i] = value * db2level(-16);
samples_2db[i] = value * db2level(-2);
samples_8db[i] = value * db2level(-8);
samples_0db[i] = value;
}
}
static void check_level(sample_t *samples, double duration, const char *desc, double target_db)
{
int i;
double last = 0.0, envelop = 0.0;
int up = 0;
double factor;
int when = (int)((double)SAMPLERATE + (double)SAMPLERATE * duration / 1000.0 + 0.5);
//printf("%d %d\n", SAMPLERATE, when);
for (i = 0; i < when; i++) {
//puts(debug_amplitude(samples[i]));
if (last < samples[i]) {
up = 1;
} else if (last > samples[i]) {
if (up) {
envelop = last;
}
up = 0;
}
#if 0
if (i >= (SAMPLERATE-(SAMPLERATE/100)) && (i % (SAMPLERATE/(SAMPLERATE/10))) == 0)
printf("%s: envelop = %.4f (val=%.4f) (when=%d)\n", desc, level2db(envelop), envelop, i);
#endif
last = samples[i];
}
factor = envelop / db2level(target_db);
printf("%s: envelop after the instance of %.1f ms is %.4f db factor =%.4f\n", desc, duration, level2db(envelop), factor);
}
int main(void)
{
compandor_t cstate;
sample_t samples[SAMPLERATE * 2];
int f;
init_compandor(&cstate, SAMPLERATE, ATTACK_MS, RECOVERY_MS);
for (f = 0; f < 3; f++) {
/* -16 and -4 dB */
printf("Testing frequency %.0f Hz:\n", test_frequency[f]);
generate_test_sample(test_frequency[f]);
#if 0
check_level(samples_0db, -100.0, "generate sample with 0db", 0.0);
check_level(samples_2db, -100.0, "generate sample with -2db", -2.0);
check_level(samples_4db, -100.0, "generate sample with -4db", -4.0);
check_level(samples_8db, -100.0, "generate sample with -8db", -8.0);
check_level(samples_16db, -100.0, "generate sample with -16db", -16.0);
#endif
/* low to high transition */
memcpy(samples, samples_16db, SAMPLERATE * sizeof(sample_t));
memcpy(samples + SAMPLERATE, samples_4db, SAMPLERATE * sizeof(sample_t));
compress_audio(&cstate, samples, SAMPLERATE * 2);
check_level(samples, ATTACK_MS, "compressor attack", -2.0);
/* high to low transition */
memcpy(samples, samples_4db, SAMPLERATE * sizeof(sample_t));
memcpy(samples + SAMPLERATE, samples_16db, SAMPLERATE * sizeof(sample_t));
compress_audio(&cstate, samples, SAMPLERATE * 2);
check_level(samples, RECOVERY_MS, "compressor recovery", -8.0);
/* low to high transition */
memcpy(samples, samples_8db, SAMPLERATE * sizeof(sample_t));
memcpy(samples + SAMPLERATE, samples_2db, SAMPLERATE * sizeof(sample_t));
expand_audio(&cstate, samples, SAMPLERATE * 2);
check_level(samples, ATTACK_MS, "expander attack", -4.0);
/* high to low transition */
memcpy(samples, samples_2db, SAMPLERATE * sizeof(sample_t));
memcpy(samples + SAMPLERATE, samples_8db, SAMPLERATE * sizeof(sample_t));
expand_audio(&cstate, samples, SAMPLERATE * 2);
check_level(samples, RECOVERY_MS, "expander recovery", -16.0);
/* 0 DB */
memcpy(samples, samples_0db, SAMPLERATE * sizeof(sample_t));
memcpy(samples + SAMPLERATE, samples_0db, SAMPLERATE * sizeof(sample_t));
check_level(samples, RECOVERY_MS, "unaffected level", 0.0);
puts("");
}
return 0;
}