better autotune speed

Source/Shifter.cpp

@@ -6,6 +6,58 @@
 #define PI_F 3.1415927410125732421875f
 #endif
 
+
+class MidiPitchSmoother {
+public:
+
+    MidiPitchSmoother() {
+        tau = .1;
+        dt = 2048.0f / 48000.0f;
+        PcorrPrev = 60.0f;
+		PtargPrev = 60;
+    }
+    void SetFrameTime(float frame_time) {
+        dt = frame_time;
+	}
+
+    void SetTimeConstant(float t) {
+		tau = t;
+    }
+    float update(float Pdet, int Ptarget) {
+        // Detect large jump (new note)
+        float diff = std::fabs(Pdet - PcorrPrev);
+        if (Ptarget != PtargPrev) {
+            // Immediately reset to new note
+            PcorrPrev = Pdet;
+            PtargPrev = Ptarget;
+            return PcorrPrev;
+        }
+
+        // Compute smoothing coefficient
+        float alpha = 1.0 - std::exp(-dt / tau);
+
+        // Smooth within same note
+        float PcorrNew = PcorrPrev + alpha * (Ptarget - PcorrPrev);
+
+        PcorrPrev = PcorrNew;
+        return PcorrNew;
+    }
+
+    
+private:
+
+    float tau;          // Time constant (s)
+    float dt;           // Frame time (s)
+    float PcorrPrev;    // Previous corrected pitch (MIDI)
+    int PtargPrev;    // Previous corrected pitch (MIDI)
+};
+
+MidiPitchSmoother out_midi_smoother;
+
+void Shifter::SetAutoTuneSpeed(float val) {
+	out_midi_smoother.SetTimeConstant(val);
+}
+
 static inline float mtof(float m)
 {
     return powf(2, (m - 69.0f) / 12.0f) * 440.0f;
@@ -90,7 +142,7 @@ void Shifter::DetectPitch(const float* const* in, float** out, size_t size)
     //DBG("frequency: " << 48000 / period << " fidel: " << fidel);
 
     // Adjustable filter amount (0.0f = no filtering, 1.0f = max filtering)
-    static float in_period_filter_amount = 0.7f; // You can expose this as a parameter
+    static float in_period_filter_amount = 0.0f; // You can expose this as a parameter
 
     if (fidel > 0.95) {
         // Smoothly filter in_period changes
@@ -98,20 +150,11 @@ void Shifter::DetectPitch(const float* const* in, float** out, size_t size)
     }
     float in_freq = 48000 / in_period;
     
-    int midi = (int)(12 * log2f(in_freq / 440) + 69.5f);
+    float midi = (12 * log2f(in_freq / 440) + 69.0f);
-    float target_out_period = 48000.0f / mtof(midi);
-	
-    if (midi != last_autotune_midi) {
-        last_autotune_midi = midi;
-        out_period = in_period;
-    }
-
-	float error = target_out_period - out_period;
-    float adjustment = error * out_period_filter_amount;
 
     //target_out_period = in_period * out_period_filter_amount + target_out_period * (1 - out_period_filter_amount);
-    out_midi = midi;
+    out_midi = out_midi_smoother.update(midi, (int)(midi+.5));
-	out_period += adjustment;
+	out_period = 48000.0f / mtof(out_midi);
 }
 
 void Shifter::SetRates() {}

Source/Shifter.h

@@ -83,9 +83,9 @@ public:
     void AddMidiNote(int note);
     void RemoveMidiNote(int note);
 	void SetFormantPreserve(float val) { formant_preserve = val; }
-    void SetAutoTuneSpeed(float val) { out_period_filter_amount = 1 - val; }
+    void SetAutoTuneSpeed(float val);
 
-    int out_midi = -1;
+    float out_midi = 40;
 
 private:
     void DetectPitch(const float* const* in, float** out, size_t size);

Source/WebViewPluginDemo.h

@@ -213,7 +213,7 @@ public:
 			autoTuneSpeed(addToLayout<AudioParameterFloat>(layout,
 				ID::autoTuneSpeed,
 				"AutoTune Speed",
-				NormalisableRange<float> {0.0f, 1.0f, .01f},
+				NormalisableRange<float> {0.001f, 0.4f, .01f},
 				.5f)),
 			mute(addToLayout<AudioParameterBool>(layout, ID::mute, "Mute", false)),
 			filterType(addToLayout<AudioParameterChoice>(layout,