fixed polyblep/antialiased oscillator issues

Author: Martin Klang

LibSource/Oscillator.h

@@ -121,20 +121,21 @@ class OscillatorTemplate : public BaseOscillator {
     delete osc;
   }
 protected:
+  /** 
+   * Calculate poly blep antialiasing compensation on normalised (to range [0, 1])
+   * phase and phase increment (angular rate) values.
+   */
   static float polyblep(float t, float dt){
     // PolyBLEP by various
     // http://research.spa.aalto.fi/publications/papers/smc2010-phaseshaping/
     // https://www.kvraudio.com/forum/viewtopic.php?t=375517
     // http://www.martin-finke.de/blog/articles/audio-plugins-018-polyblep-oscillator/
     // https://www.metafunction.co.uk/post/all-about-digital-oscillators-part-2-blits-bleps
-    // if t and dt are normalised before call then end/begin phase are not needed    
-    if(t < T::begin_phase + dt){
-      dt = dt / (T::end_phase - T::begin_phase); // normalise phase increment
-      t = (t - T::begin_phase) / dt; // distance from discontinuity
+    if(t < dt){
+      t /= dt;
       return t+t - t*t - 1;
-    }else if(t > T::end_phase - dt){
-      dt = dt / (T::end_phase - T::begin_phase); // normalise phase increment
-      t = (t - T::end_phase) / dt; // distance from discontinuity
+    }else if(t > 1 - dt){
+      t = (t - 1) / dt;
       return t*t + t+t + 1;
     }
     return 0;

LibSource/RampOscillator.h

@@ -35,12 +35,14 @@ class InvertedRampOscillator : public OscillatorTemplate<InvertedRampOscillator>
   }
 };
 
-class AntialisedRampOscillator : public OscillatorTemplate<AntialisedRampOscillator> {
+class AntialiasedRampOscillator : public OscillatorTemplate<AntialiasedRampOscillator> {
 public:
-  static constexpr float begin_phase = -1;
+  static constexpr float begin_phase = 0;
   static constexpr float end_phase = 1;
   float getSample(){
-    return phase - polyblep(phase, incr);
+    float sample = 2*phase-1; // naive ramp
+    sample -= polyblep(phase, incr);
+    return sample;
   }
 };
 

LibSource/SquareWaveOscillator.h

@@ -55,8 +55,8 @@ class AntialiasedSquareWaveOscillator : public OscillatorTemplate<AntialiasedSqu
   }
   float getSample(){
     float sample = phase < pw ? 1 : -1;
-    sample += polyblep(incr, phase);
-    sample -= polyblep(incr, fmod(phase + 1 + pw, 2));
+    sample += polyblep(phase, incr);
+    sample -= polyblep(fmod(phase + 1 - pw, 1), incr);
     return sample;
   }
 };

LibSource/TapTempo.h

@@ -115,12 +115,20 @@ class AdjustableTapTempo : public TapTempo {
 public:
   AdjustableTapTempo(float sr, size_t min, size_t max) :
     TapTempo(sr, min, max), speed(scale(0.5f)) {}
+  [[deprecated("use resetSpeed() instead.")]]  
+  void resetAdjustment(uint16_t s){
+    resetSpeed(s/4096.0f);
+  }
   void resetSpeed(float s){
     speed = scale(s);
   }
   void setRange(float value){
     range = value*0.75f;
   }
+  [[deprecated("use adjustSpeed() instead.")]]  
+  void adjust(uint16_t s){
+    adjustSpeed(s/4096.0f);
+  }
   /**
    * Adjust the tap tempo period.
    * @param speed should be in the range [0, 1]

LibSource/TriangleOscillator.h

@@ -18,26 +18,17 @@ class TriangleOscillator : public OscillatorTemplate<TriangleOscillator> {
 
 class AntialiasedTriangleOscillator : public OscillatorTemplate<AntialiasedTriangleOscillator> {
 protected:
-  float pw = 0.5f;
   float previousSample = 0;
 public:
   static constexpr float begin_phase = 0;
   static constexpr float end_phase = 1;
-  /**
-   * Set pulse width to a value between 0 and 1
-   */
-  void setPulseWidth(float value){
-    pw = value;
-  }
   float getSample(){
-    float sample = phase < pw ? 1 : -1;
-    sample += polyblep(incr, phase);
-    sample -= polyblep(incr, fmod(phase + 1 + pw, 2));
+    float sample = phase < 0.5f ? 1 : -1; // naive square wave
+    sample += polyblep(phase, incr);
+    sample -= polyblep(fmod(phase + 0.5f, 1), incr); // polyblep square wave
     // Leaky integrator: y[n] = A * x[n] + (1 - A) * y[n-1] = A * (x[n] - y[n-1]) + y[n-1]
-    float lambda = incr;
-    // float lambda = incr*2*M_PI;
-    sample = lambda * sample + (1 - lambda) * previousSample;
-    // sample = lambda * (sample - previousSample) + previousSample;
+    float lambda = incr*2*M_PI;
+    sample = lambda * (sample - previousSample) + previousSample;
     previousSample = sample;
     return sample;
   }