fm95/lib/fm_modulator.c

#include "fm_modulator.h"

void init_fm_modulator(FMModulator *fm, float frequency, float deviation, float sample_rate) {
	fm->frequency = frequency;
	fm->deviation = deviation;
	fm->sample_rate = sample_rate;
	fm->osc_phase = 0.0f;
}

float modulate_fm(FMModulator *fm, float sample) {
	float inst_freq = fm->frequency+(sample*fm->deviation);
	if (inst_freq < 0.0f) inst_freq = 0.0f;
	float out = sinf(fm->osc_phase);
	fm->osc_phase = fmodf(fm->osc_phase + ((M_2PI * inst_freq) / fm->sample_rate), M_2PI);
	return out;
}