Phaser (electro-smith#133)

* compiling

* allpass

* freq conversion

* crunch bug

* still broke

* add phaser to make and daisysp.h, remove phaser include paths

* formatting

* change phaser.h delayline include to relative path

* fix phaser SetFreq clipping bug

* move hz to deltime conversion to last second

* add fonepole to mitigate lfo crunch around -1

* style to appease the robots

* fixed init and replaced MAX POLES macro with internal static constexpr

Co-authored-by: stephenhensley <stephen.p.hensley@gmail.com>

Makefile

@@ -37,6 +37,7 @@ decimator \
 flanger \
 fold \
 overdrive \
+phaser \
 reverbsc \
 sampleratereducer \
 tremolo 

Source/Effects/phaser.cpp

@@ -0,0 +1,138 @@
+#include "dsp.h"
+#include "phaser.h"
+#include <math.h>
+
+using namespace daisysp;
+
+//PhaserEngine stuff
+void PhaserEngine::Init(float sample_rate)
+{
+    sample_rate_ = sample_rate;
+
+    del_.Init();
+    lfo_amp_  = 0.f;
+    feedback_ = .2f;
+    SetFreq(200.f);
+
+    del_.SetDelay(0.f);
+
+    os_ = 30.f; //30 hertz frequency offset, lower than this introduces crunch
+    deltime_ = 0.f;
+
+    last_sample_ = 0.f;
+    lfo_phase_   = 0.f;
+    SetLfoFreq(.3);
+    SetLfoDepth(.9);
+}
+
+float PhaserEngine::Process(float in)
+{
+    float lfo_sig = ProcessLfo();
+    fonepole(deltime_, sample_rate_ / (lfo_sig + ap_freq_ + os_), .0001f);
+
+    last_sample_ = del_.Allpass(in + feedback_ * last_sample_, deltime_, .3f);
+
+    return (in + last_sample_) * .5f; //equal mix
+}
+
+void PhaserEngine::SetLfoDepth(float depth)
+{
+    lfo_amp_ = fclamp(depth, 0.f, 1.f);
+}
+
+void PhaserEngine::SetLfoFreq(float lfo_freq)
+{
+    lfo_freq = 4.f * lfo_freq / sample_rate_;
+    lfo_freq *= lfo_freq_ < 0.f ? -1.f : 1.f; //if we're headed down, keep going
+    lfo_freq_ = fclamp(lfo_freq, -.25f, .25f); //clip at +/- .125 * sr
+}
+
+void PhaserEngine::SetFreq(float ap_freq)
+{
+    ap_freq_ = fclamp(ap_freq, 0.f, 20000.f); //0 - 20kHz
+}
+
+void PhaserEngine::SetFeedback(float feedback)
+{
+    feedback_ = fclamp(feedback, 0.f, .75f);
+}
+
+float PhaserEngine::ProcessLfo()
+{
+    lfo_phase_ += lfo_freq_;
+
+    //wrap around and flip direction
+    if(lfo_phase_ > 1.f)
+    {
+        lfo_phase_ = 1.f - (lfo_phase_ - 1.f);
+        lfo_freq_ *= -1.f;
+    }
+    else if(lfo_phase_ < -1.f)
+    {
+        lfo_phase_ = -1.f - (lfo_phase_ + 1.f);
+        lfo_freq_ *= -1.f;
+    }
+
+    return lfo_phase_ * lfo_amp_ * ap_freq_;
+}
+
+//Phaser Stuff
+void Phaser::Init(float sample_rate)
+{
+    for(size_t i = 0; i < kMaxPoles; i++)
+    {
+        engines_[i].Init(sample_rate);
+    }
+
+    poles_     = 4;
+    gain_frac_ = .5f;
+}
+
+float Phaser::Process(float in)
+{
+    float sig = 0.f;
+
+    for(int i = 0; i < poles_; i++)
+    {
+        sig += engines_[i].Process(in);
+    }
+
+    return sig;
+}
+
+void Phaser::SetPoles(int poles)
+{
+    poles_ = DSY_CLAMP(poles, 1, 8);
+}
+
+void Phaser::SetLfoDepth(float depth)
+{
+    for(int i = 0; i < kMaxPoles; i++)
+    {
+        engines_[i].SetLfoDepth(depth);
+    }
+}
+
+void Phaser::SetLfoFreq(float lfo_freq)
+{
+    for(int i = 0; i < kMaxPoles; i++)
+    {
+        engines_[i].SetLfoFreq(lfo_freq);
+    }
+}
+
+void Phaser::SetFreq(float ap_freq)
+{
+    for(int i = 0; i < kMaxPoles; i++)
+    {
+        engines_[i].SetFreq(ap_freq);
+    }
+}
+
+void Phaser::SetFeedback(float feedback)
+{
+    for(int i = 0; i < kMaxPoles; i++)
+    {
+        engines_[i].SetFeedback(feedback);
+    }
+}

Source/Effects/phaser.h

@@ -0,0 +1,131 @@
+#pragma once
+#ifndef DSY_PHASER_H
+#define DSY_PHASER_H
+#ifdef __cplusplus
+
+#include <stdint.h>
+#include "Utility/delayline.h"
+
+/** @file phaser.h */
+
+namespace daisysp
+{
+/**  
+    @brief Single Phaser engine. Used in Phaser.
+    @author Ben Sergentanis
+*/
+class PhaserEngine
+{
+  public:
+    PhaserEngine() {}
+    ~PhaserEngine() {}
+
+    /** Initialize the module
+        \param sample_rate Audio engine sample rate.
+    */
+    void Init(float sample_rate);
+
+    /** Get the next sample
+        \param in Sample to process
+    */
+    float Process(float in);
+
+    /** How much to modulate the allpass filter by.
+        \param depth Works 0-1.
+    */
+    void SetLfoDepth(float depth);
+
+    /** Set lfo frequency.
+        \param lfo_freq Frequency in Hz
+    */
+    void SetLfoFreq(float lfo_freq);
+
+    /** Set the allpass frequency
+        \param ap_freq Frequency in Hz.
+    */
+    void SetFreq(float ap_freq);
+
+    /** Set the feedback amount.
+        \param feedback Amount from 0-1.
+    */
+    void SetFeedback(float feedback);
+
+  private:
+    float                    sample_rate_;
+    static constexpr int32_t kDelayLength
+        = 2400; // 50 ms at 48kHz = .05 * 48000
+
+    //triangle lfo
+    float lfo_phase_;
+    float lfo_freq_;
+    float lfo_amp_;
+
+    float os_;
+
+    float feedback_;
+    float ap_freq_;
+
+    float deltime_;
+    float last_sample_;
+
+    DelayLine<float, kDelayLength> del_;
+
+    float ProcessLfo();
+};
+
+//wraps up all of the phaser engines
+/**  
+    @brief Phaser Effect.
+    @author Ben Sergentanis
+    @date Jan 2021
+*/
+class Phaser
+{
+  public:
+    Phaser() {}
+    ~Phaser() {}
+
+    /** Initialize the module
+        \param sample_rate Audio engine sample rate
+    */
+    void Init(float sample_rate);
+
+    /** Get the next floating point sample.
+        \param in Sample to process
+    */
+    float Process(float in);
+
+    /** Number of allpass stages.
+        \param poles Works 1 to 8.
+    */
+    void SetPoles(int poles);
+
+    /** Set all lfo depths
+        \param depth Works 0-1.
+    */
+    void SetLfoDepth(float depth);
+
+    /** Set all lfo frequencies.
+        \param lfo_freq Lfo freq in Hz.
+    */
+    void SetLfoFreq(float lfo_freq);
+
+    /** Set all channel allpass freq in Hz.
+        \param ap_freq Frequency in Hz.
+    */
+    void SetFreq(float ap_freq);
+
+    /** Set all channels feedback.
+        \param feedback Works 0-1.
+    */
+    void SetFeedback(float feedback);
+
+  private:
+    static constexpr int kMaxPoles = 8;
+    PhaserEngine         engines_[kMaxPoles];
+    float                gain_frac_;
+    int                  poles_;
+};
+} //namespace daisysp
+#endif
+#endif

Source/daisysp.h

@@ -43,6 +43,7 @@
 #include "Effects/fold.h"
 #include "Effects/overdrive.h"
 #include "Effects/reverbsc.h"
+#include "Effects/phaser.h"
 #include "Effects/pitchshifter.h"
 #include "Effects/sampleratereducer.h"
 #include "Effects/tremolo.h"