maybe the darc will come

README.md

@@ -3,6 +3,7 @@
 FM95 is a audio processor for FM, it does:
 
 - Pre-Emphasis
+- Low Pass Filtering
 - Stereo
 - Polar Stereo
 - SCA

dsp/fm_modulator.c

@@ -12,4 +12,20 @@ float modulate_fm(FMModulator *fm, float sample) {
 	fm->osc_phase += (M_2PI * inst_freq) / fm->sample_rate;
 	fm->osc_phase -= (fm->osc_phase >= M_2PI) ? M_2PI : 0.0f;
 	return sinf(fm->osc_phase);
+}
+
+void init_refrenced_fm_modulator(RefrencedFMModulator* fm, Oscillator* osc, float deviation) {
+	fm->deviation = deviation;
+	fm->osc = osc;
+}
+
+float refrenced_modulate_fm(RefrencedFMModulator* fm, float sample) {
+    float inst_freq = sample * fm->deviation;
+    float phase = fm->osc->phase + ((M_2PI * inst_freq) / fm->osc->sample_rate);
+    
+    if (phase >= M_2PI) {
+        phase -= M_2PI;
+    }
+    
+    return sinf(phase);
 }

dsp/fm_modulator.h

@@ -11,4 +11,12 @@ typedef struct
 } FMModulator;
 
 void init_fm_modulator(FMModulator *fm, float frequency, float deviation, float sample_rate);
-float modulate_fm(FMModulator *fm, float sample);
+float modulate_fm(FMModulator *fm, float sample);
+
+typedef struct
+{
+	float deviation;
+	Oscillator* osc;
+} RefrencedFMModulator;
+void init_refrenced_fm_modulator(RefrencedFMModulator *fm, Oscillator *osc, float deviation);
+float refrenced_modulate_fm(RefrencedFMModulator *fm, float sample);

src/fm95.c

@@ -450,23 +450,22 @@ int main(int argc, char **argv) {
 
 			float mono = (ready_l + ready_r) / 2.0f;
 			audio = mono*MONO_VOLUME;
-			float stereo_carrier = 0.0f;
 			if(stereo) {
 				float stereo = (ready_l - ready_r) / 2.0f;
-				stereo_carrier = get_oscillator_sin_multiplier_ni(&osc, polar_stereo ? 1 : 8);
+				float stereo_carrier = get_oscillator_sin_multiplier_ni(&osc, polar_stereo ? 1 : 8); // 31.25 or 38 KHz
 
 				if(polar_stereo) audio += ((stereo+0.2)*stereo_carrier)*STEREO_VOLUME;
 				else {
-					float pilot = get_oscillator_sin_multiplier_ni(&osc, 4);
+					float pilot = get_oscillator_sin_multiplier_ni(&osc, 4); // 19 KHz
 					mpx += pilot*PILOT_VOLUME;
 					audio += (stereo*stereo_carrier)*STEREO_VOLUME;
 				}
 			}
 			if(rds_on && polar_stereo == 0) {
-				float rds_carrier = get_oscillator_cos_multiplier_ni(&osc, 12);
+				float rds_carrier = get_oscillator_cos_multiplier_ni(&osc, 12); // 57 KHz
 				mpx += (current_rds_in*rds_carrier)*RDS_VOLUME;
 				if(!sca_on) {
-					float rds2_carrier_66 = get_oscillator_cos_multiplier_ni(&osc, 14);
+					float rds2_carrier_66 = get_oscillator_cos_multiplier_ni(&osc, 14); // 66.5 KHz
 					mpx += (current_rds2_in*rds2_carrier_66)*RDS2_VOLUME;
 				}
 			}
@@ -502,6 +501,7 @@ int main(int argc, char **argv) {
 	iirfilt_rrrf_destroy(lpf_l);
 	iirfilt_rrrf_destroy(lpf_r);
 	iirfilt_rrrf_destroy(mpx_lpf);
+
 	free_PulseInputDevice(&input_device);
 	if(mpx_on) free_PulseInputDevice(&mpx_device);
 	if(rds_on) free_PulseInputDevice(&rds_device);