fm95/lib/bs412.c

#include "bs412.h"

float dbr_to_deviation(float dbr) {
	return (19000.0f * 0.70710678f) * powf(10.0f, dbr / 20.0f);
}

float deviation_to_dbr(float deviation) {
	return 20 * log10f((deviation + 1e-6f) / (19000.0f * 0.70710678f));
}

void init_modulation_power_measure(MPXPowerMeasurement* mpx, int sample_rate) {
	mpx->i = 1;
	mpx->sample = 0;
	mpx->sample_rate = sample_rate;
}

float measure_mpx(MPXPowerMeasurement* mpx, float deviation) {
    mpx->sample += deviation * deviation;
    mpx->i++;

    float avg_deviation = sqrtf(mpx->sample / mpx->i);
    float modulation_power = deviation_to_dbr(avg_deviation);

    if (mpx->i >= mpx->sample_rate * 60) {
        mpx->sample = 0;
        mpx->i = 0;
    }

    return modulation_power;
}