wip: phase accumulated osc

main.c

@@ -109,7 +109,7 @@ SynthSound note(Synth* synth, int semitone, float beats) {
     
     // will change after oscillator starts to be more autonomous
     for (size_t i = 0; i < synth->oscillators.count; i++) {
-        synth->oscillators.array[i].freq = hz;
+        osc_set_freq(&synth->oscillators.array[i], hz);
     }
 
     return freq(duration, synth->oscillators);

oscillator.c

@@ -3,6 +3,8 @@
 #include "math.h"
 #include "stdlib.h"
 
+#define TWO_PI 2*SYNTH_PI
+
 static SynthSound get_init_samples(float duration) {
     size_t sample_count = (size_t)(duration * SAMPLE_RATE);
     float* samples = malloc(sizeof(float) * sample_count);
@@ -23,42 +25,96 @@ static float pos(float hz, float x) {
     return fmodf(hz * x / SAMPLE_RATE, 1);
 }
 
-static float sineosc(float hz, float x) {
+static void sine_osc_phase_incr(Oscillator* osc) {
-    return sinf(x * (2.f * SYNTH_PI * hz / SAMPLE_RATE));
+    osc->phase += osc->phase_dt;
+    if (osc->phase >= TWO_PI)
+        osc->phase -= TWO_PI;
+}
+
+static void saw_osc_phase_incr(Oscillator* osc) {
+    osc->phase += osc->phase_dt;
+    if (osc->phase >= 1.0f)
+        osc->phase -= 1.0f;
+}
+
+static float calc_saw_phase_delta(float freq) {
+    return freq / SAMPLE_RATE;
+}
+
+static float calc_sine_phase_delta(float freq) {
+    return (TWO_PI * freq) / SAMPLE_RATE;
+}
+
+static float sineosc(Oscillator* osc) {
+    float result = sinf(osc->phase);
+    sine_osc_phase_incr(osc);
+    return result;
 }
 
 static float sign(float v) {
     return (v > 0.0) ? 1.f : -1.f;
 }
 
-static float squareosc(float hz, float x) {
+static float squareosc(Oscillator* osc) {
-    return sign(sineosc(hz, x));
+    return sign(sineosc(osc));
 }
 
-static float triangleosc(float hz, float x) {
+static float triangleosc(Oscillator* osc) {
-    return 1.f - fabsf(pos(hz, x) - 0.5f) * 4.f;
+    float result = 1.f - fabsf(osc->phase - 0.5f) * 4.f;
+    saw_osc_phase_incr(osc);
+    return result;
 }
 
-static float sawosc(float hz, float x) {
+static float sawosc(Oscillator* osc) {
-    return pos(hz, x) * 2.f - 1.f;
+    float result = osc->phase * 2.f - 1.f;
+    saw_osc_phase_incr(osc);
+    return result;
+}
+
+void osc_set_freq(Oscillator* osc, float freq) {
+    osc->freq = freq;
+    osc->phase = 0;
+    switch (osc->osc)
+    {
+        case Sine:
+            osc->phase_dt = calc_sine_phase_delta(freq);
+            break;
+        case Square:
+            osc->phase_dt = calc_sine_phase_delta(freq);
+            break;
+        case Triangle:
+            osc->phase_dt = calc_saw_phase_delta(freq);
+            break;
+        case Saw:
+            osc->phase_dt = calc_saw_phase_delta(freq);
+            break;
+        default:
+            break;
+    }
+}
+
+void osc_reset(Oscillator* osc) {
+    osc->volume = 0;
+    osc->phase = 0;
+    osc->phase_dt = 0;
 }
 
 float multiosc(OscillatorGenerationParameter param) {
     float osc_sample = 0.f;
     for (size_t i = 0; i < param.oscillators.count; i++) {
-        Oscillator osc = param.oscillators.array[i];
+        Oscillator* osc = &param.oscillators.array[i];
-        switch (osc.osc) {
+        switch (osc->osc) {
             case Sine:
-                osc_sample += sineosc(osc.freq, param.sample) * osc.volume;
+                osc_sample += sineosc(osc) * osc->volume;
                 break;
             case Triangle:
-                osc_sample += triangleosc(osc.freq, param.sample) * osc.volume;
+                osc_sample += triangleosc(osc) * osc->volume;
                 break;
             case Square:
-                osc_sample += squareosc(osc.freq, param.sample) * osc.volume;
+                osc_sample += squareosc(osc) * osc->volume;
                 break;
             case Saw:
-                osc_sample += sawosc(osc.freq, param.sample) * osc.volume;
+                osc_sample += sawosc(osc) * osc->volume;
                 break;
         }
     }

oscillator.h

@@ -14,6 +14,8 @@ typedef struct Oscillator {
     OscillatorType osc;
     float freq;
     float volume;
+    float phase;
+    float phase_dt;
 } Oscillator;
 
 typedef struct OscillatorArray {
@@ -26,6 +28,8 @@ typedef struct OscillatorGenerationParameter {
     float sample;
 } OscillatorGenerationParameter;
 
+void osc_set_freq(Oscillator* osc, float freq);
+void osc_reset(Oscillator* osc);
 float multiosc(OscillatorGenerationParameter param);
 SynthSound freq(float duration, OscillatorArray osc);