feat: all filter types

closes #19

Reviewed-on: #22

.gitignore

@@ -3,4 +3,5 @@
 /Debug/
 *.wav
 *.dSYM
-/lib
+/lib
+/build

CMakeLists.txt

@@ -0,0 +1,37 @@
+cmake_minimum_required(VERSION 3.5)
+project(SeeSynth)
+#set(CMAKE_C_STANDARD 99)
+
+# Adding Raylib
+include(FetchContent)
+set(FETCHCONTENT_QUIET FALSE)
+set(BUILD_EXAMPLES OFF CACHE BOOL "" FORCE) # don't build the supplied examples
+set(BUILD_GAMES    OFF CACHE BOOL "" FORCE) # don't build the supplied example games
+
+FetchContent_Declare(
+    raylib
+    GIT_REPOSITORY "https://github.com/raysan5/raylib.git"
+    GIT_TAG "4.5.0"
+    GIT_PROGRESS TRUE
+)
+
+FetchContent_MakeAvailable(raylib)
+
+# Adding our source files
+file(GLOB_RECURSE PROJECT_SOURCES CONFIGURE_DEPENDS "${CMAKE_CURRENT_LIST_DIR}/src/*.cpp") # Define PROJECT_SOURCES as a list of all source files
+set(PROJECT_INCLUDE "${CMAKE_CURRENT_LIST_DIR}/inc/") # Define PROJECT_INCLUDE to be the path to the include directory of the project
+
+
+# Declaring our executable
+add_executable(${PROJECT_NAME})
+set_target_properties(
+    ${PROJECT_NAME} PROPERTIES
+    CXX_STANDARD 17
+    CXX_STANDARD_REQUIRED ON)
+target_sources(${PROJECT_NAME} PRIVATE ${PROJECT_SOURCES})
+target_include_directories(${PROJECT_NAME} PRIVATE ${PROJECT_INCLUDE})
+target_link_libraries(${PROJECT_NAME} PRIVATE raylib)
+
+# Setting ASSETS_PATH
+target_compile_definitions(${PROJECT_NAME} PUBLIC ASSETS_PATH="${CMAKE_CURRENT_SOURCE_DIR}/assets/") # Set the asset path macro to the absolute path on the dev machine
+#target_compile_definitions(${PROJECT_NAME} PUBLIC ASSETS_PATH="./assets") # Set the asset path macro in release mode to a relative path that assumes the assets folder is in the same directory as the game executable

docs/StateVariableFilter.md

@@ -0,0 +1,214 @@
+https://www.earlevel.com/main/2003/03/02/the-digital-state-variable-filter/
+
+The frequency control coefficient, f, is defined as
+
+![Alt text](image.png)
+
+where Fs is the sample rate and Fc is the filter’s corner frequency you want to set. The q coefficient is defined as
+
+![Alt text](image-1.png)
+
+where Q normally ranges from 0.5 to inifinity (where the filter oscillates).
+
+
+The main drawback of the digital state variable is that it becomes unstable at higher frequencies. It depends on the Q setting, but basically the upper bound of stability is about where f reaches 1, which is at one-sixth of the sample rate (8 kHz at 48 kHz). The only way around this is to oversample. A simple way to double the filter’s sample rate (and thereby double the filter’s frequency range) is to run the filter twice with the same input sample, and discard one output sample.
+
+
+
+example with double-sampling
+
+```
+input  = input buffer;
+output = output buffer;
+fs     = sampling frequency;
+fc     = cutoff frequency normally something like:
+         440.0*pow(2.0, (midi_note - 69.0)/12.0);
+res    = resonance 0 to 1;
+drive  = internal distortion 0 to 0.1
+freq   = 2.0*sin(PI*MIN(0.25, fc/(fs*2)));  // the fs*2 is because it's double sampled
+damp   = MIN(2.0*(1.0 - pow(res, 0.25)), MIN(2.0, 2.0/freq - freq*0.5));
+notch  = notch output
+low    = low pass output
+high   = high pass output
+band   = band pass output
+peak   = peaking output = low - high
+--
+double sampled svf loop:
+for (i=0; i<numSamples; i++)
+{
+  in    = input[i];
+  notch = in - damp*band;
+  low   = low + freq*band;
+  high  = notch - low;
+  band  = freq*high + band - drive*band*band*band;
+  out   = 0.5*(notch or low or high or band or peak);
+  notch = in - damp*band;
+  low   = low + freq*band;
+  high  = notch - low;
+  band  = freq*high + band - drive*band*band*band;
+  out  += 0.5*(same out as above);
+  output[i] = out;
+}
+```
+
+
+Also that could work as it's a voltage-controlled filter
+https://www.musicdsp.org/en/latest/Filters/24-moog-vcf.html
+
+```
+//Init
+cutoff = cutoff freq in Hz
+fs = sampling frequency //(e.g. 44100Hz)
+res = resonance [0 - 1] //(minimum - maximum)
+
+f = 2 * cutoff / fs; //[0 - 1]
+k = 3.6*f - 1.6*f*f -1; //(Empirical tunning)
+p = (k+1)*0.5;
+scale = e^((1-p)*1.386249;
+r = res*scale;
+y4 = output;
+
+y1=y2=y3=y4=oldx=oldy1=oldy2=oldy3=0;
+
+//Loop
+//--Inverted feed back for corner peaking
+x = input - r*y4;
+
+//Four cascaded onepole filters (bilinear transform)
+y1=x*p + oldx*p - k*y1;
+y2=y1*p+oldy1*p - k*y2;
+y3=y2*p+oldy2*p - k*y3;
+y4=y3*p+oldy3*p - k*y4;
+
+//Clipper band limited sigmoid
+y4 = y4 - (y4^3)/6;
+
+oldx = x;
+oldy1 = y1;
+oldy2 = y2;
+oldy3 = y3;
+```
+
+
+```
+#pragma once
+
+namespace DistoCore
+{
+  template<class T>
+  class MoogFilter
+  {
+  public:
+    MoogFilter();
+    ~MoogFilter() {};
+
+    T getSampleRate() const { return sampleRate; }
+    void setSampleRate(T fs) { sampleRate = fs; calc(); }
+    T getResonance() const { return resonance; }
+    void setResonance(T filterRezo) { resonance = filterRezo; calc(); }
+    T getCutoff() const { return cutoff; }
+    T getCutoffHz() const { return cutoff * sampleRate * 0.5; }
+    void setCutoff(T filterCutoff) { cutoff = filterCutoff; calc(); }
+
+    void init();
+    void calc();
+    T process(T input);
+    // filter an input sample using normalized params
+    T filter(T input, T cutoff, T resonance);
+
+  protected:
+    // cutoff and resonance [0 - 1]
+    T cutoff;
+    T resonance;
+    T sampleRate;
+    T fs;
+    T y1,y2,y3,y4;
+    T oldx;
+    T oldy1,oldy2,oldy3;
+    T x;
+    T r;
+    T p;
+    T k;
+  };
+
+    /**
+     * Construct Moog-filter.
+     */
+  template<class T>
+  MoogFilter<T>::MoogFilter()
+  : sampleRate(T(44100.0))
+  , cutoff(T(1.0))
+  , resonance(T(0.0))
+  {
+    init();
+  }
+
+    /**
+     * Initialize filter buffers.
+     */
+  template<class T>
+  void MoogFilter<T>::init()
+  {
+    // initialize values
+    y1=y2=y3=y4=oldx=oldy1=oldy2=oldy3=T(0.0);
+    calc();
+  }
+
+    /**
+     * Calculate coefficients.
+     */
+  template<class T>
+  void MoogFilter<T>::calc()
+  {
+    // TODO: replace with your constant
+    const double kPi = 3.1415926535897931;
+
+    // empirical tuning
+    p = cutoff * (T(1.8) - T(0.8) * cutoff);
+    // k = p + p - T(1.0);
+    // A much better tuning seems to be:
+    k = T(2.0) * sin(cutoff * kPi * T(0.5)) - T(1.0);
+
+    T t1 = (T(1.0) - p) * T(1.386249);
+    T t2 = T(12.0) + t1 * t1;
+    r = resonance * (t2 + T(6.0) * t1) / (t2 - T(6.0) * t1);
+  };
+
+    /**
+     * Process single sample.
+     */
+  template<class T>
+  T MoogFilter<T>::process(T input)
+  {
+    // process input
+    x = input - r * y4;
+
+    // four cascaded one-pole filters (bilinear transform)
+    y1 =  x * p + oldx  * p - k * y1;
+    y2 = y1 * p + oldy1 * p - k * y2;
+    y3 = y2 * p + oldy2 * p - k * y3;
+    y4 = y3 * p + oldy3 * p - k * y4;
+
+    // clipper band limited sigmoid
+    y4 -= (y4 * y4 * y4) / T(6.0);
+
+    oldx = x; oldy1 = y1; oldy2 = y2; oldy3 = y3;
+
+    return y4;
+  }
+
+    /**
+     * Filter single sample using specified params.
+     */
+  template<class T>
+  T MoogFilter<T>::filter(T input, T filterCutoff, T filterRezo)
+  {
+    // set params first
+    cutoff = filterCutoff;
+    resonance = filterRezo;
+    calc();
+
+    return process(input);
+  }
+}
+```

docs/matrix.md

@@ -0,0 +1,19 @@
+
+//  signal -> adsr -> filter
+//    ^         ^       ^
+//    |         |       |
+//     can be modulated
+//      by lfo, or adsr
+
+
+
+у каждого из них должна быть ручка для изменения состояния
+на каждом семпле?????
+
+
+
+багует сам алгоритм изменения частоты, либо алгоритм пересчета коэфициентов фильтра
+
+
+
+

inc/ADSR.h

@@ -1,9 +1,9 @@
 #pragma once
-#include "Effect.h"
+#include "IEffect.h"
 #include "Ramp.h"
 #include <cstddef>
 
-class ADSR : public Effect {
+class ADSR : public IEffect {
     enum ADSRState { sOff, sAttack, sDecay, sSustain, sRelease };
 
   private:
@@ -14,11 +14,11 @@ class ADSR : public Effect {
     ADSRState m_state;
     Ramp* m_ramp;
 
-    void process_sample(float* sample);
-    bool is_attack_elapsed();
-    bool is_decay_elapsed();
-    bool is_release_elapsed();
-    void recheck_state();
+    void ProcessSample(float* sample);
+    bool IsAttackElapsed();
+    bool IsDecayElapsed();
+    bool IsReleaseElapsed();
+    void RecheckState();
 
   public:
     ADSR(/* args */);

inc/BandPassFilter.h

@@ -1,14 +1,17 @@
 #pragma once
+
 #include "Filter.h"
 
 class BandPassFilter : public Filter {
-  private:
-    void CalculateCoefficients() override;
+  protected:
+    float GetSampleForFilterType() override;
 
   public:
+    BandPassFilter();
     BandPassFilter(Filter* filter);
     BandPassFilter(float freq, float res, float q);
-    BandPassFilter(/* args */);
     ~BandPassFilter();
     bool IsSameFilterType(FilterType type) override { return type == BandPass; };
 };
+
+

inc/Effect.h

@@ -1,12 +0,0 @@
-#pragma once
-#include <vector>
-class Effect {
-  private:
-    /* data */
-  public:
-    Effect(/* args */){};
-    ~Effect(){};
-    virtual void Trigger(){};
-    virtual void Release(){};
-    virtual void Process(std::vector<float>& samples){};
-};

inc/Filter.h

@@ -1,35 +1,36 @@
 #pragma once
-#include "Effect.h"
+#include "IEffect.h"
+#include "Settings.h"
 
-enum FilterType {
-    LowPass,
-    BandPass,
-    HighPass
-};
+enum FilterType { LowPass, BandPass, HighPass };
 
-class Filter : public Effect {
+class Filter : public IEffect {
   protected:
-    float m_freq;  // cutoff frequency
-    float m_q;     // filter quantity (resonance)
-    float m_order; // filter order (peakGain)
-    /* todo: filter adsr */
-    float m_norm, m_v, m_k;
-    float m_a0, m_a1, m_a2, m_b1, m_b2;
-    float m_z1, m_z2;
-
-    void CalculateNormals();
-    virtual void CalculateCoefficients(){};
+    // float* m_output; // output buffer
+    float m_fs = SAMPLE_RATE; // sampling frequency;
+    float m_fc;    // cutoff frequency normally something like: 440.0*pow(2.0,
+                   // (midi_note - 69.0)/12.0);
+    float m_res;   // resonance 0 to 1;
+    float m_drive; // internal distortion 0 to 0.1
+    float m_freq;  
+    float m_damp; 
+    float m_notcho; // notch output
+    float m_lowo;   // low pass output
+    float m_higho;  // high pass output
+    float m_bando;  // band pass output
+    float m_peako;  // peaking output = low - high
+    virtual float GetSampleForFilterType(){ return 0.0; };
 
   public:
     Filter(/* args */);
     virtual ~Filter();
-    void Trigger() override;
-    void Release() override;
+    void Trigger() override final;
+    void Release() override final;
     float Process(float in);
-    void Process(std::vector<float>& samples) override;
-    void SetParameters(float freq, float res, float q);
-    float GetFreq() { return m_freq; }
-    float GetRes() { return m_q; }
-    float GetPeakGain() { return m_norm; }
-    virtual bool IsSameFilterType(FilterType type){ return false; };
+    void Process(std::vector<float>& samples) override final;
+    void SetParameters(float freq, float res, float drive);
+    float GetFreq() { return m_fc; }
+    float GetRes() { return m_res; }
+    float GetPeakGain() { return m_drive; }
+    virtual bool IsSameFilterType(FilterType type) { return false; };
 };

inc/HighPassFilter.h

@@ -2,8 +2,8 @@
 #include "Filter.h"
 
 class HighPassFilter : public Filter {
-  private:
-    void CalculateCoefficients() override;
+  protected:
+    float GetSampleForFilterType() override;
 
   public:
     HighPassFilter();

inc/IEffect.h

@@ -0,0 +1,10 @@
+#pragma once
+#include <vector>
+class IEffect {
+  private:
+    /* data */
+  public:
+    virtual void Trigger() = 0;
+    virtual void Release() = 0;
+    virtual void Process(std::vector<float>& samples) = 0;
+};

inc/KeyBoard.h

@@ -54,10 +54,9 @@ class KeyBoard {
     }
 
   public:
-    KeyBoard(/* args */);
-    ~KeyBoard();
 
-    static float GetHzBySemitone(int semitone) {
+    static float GetHzBySemitone(float semitone) {
+        //440 * Math.Pow(2, (note - 69) / 12.0) would it be better?
         return PITCH_STANDARD * powf(powf(2.f, (1.f / 12.f)), semitone);
     }
 
@@ -71,7 +70,3 @@ class KeyBoard {
         return result;
     }
 };
-
-KeyBoard::KeyBoard(/* args */) {}
-
-KeyBoard::~KeyBoard() {}

inc/LFO.h

@@ -0,0 +1,13 @@
+#pragma once
+#include "Oscillator.h"
+
+class LFO: public Oscillator
+{
+private:
+    /* data */
+public:
+    LFO(/* args */);
+    ~LFO();
+    void SetFreq(float freq) { m_phase_dt = (this->*m_dt_function)(freq); }
+};
+

inc/LowPassFilter.h

@@ -4,7 +4,7 @@
 
 class LowPassFilter : public Filter {
   protected:
-    void CalculateCoefficients() override;
+    float GetSampleForFilterType() override;
 
   public:
     LowPassFilter();
@@ -13,3 +13,4 @@ class LowPassFilter : public Filter {
     ~LowPassFilter();
     bool IsSameFilterType(FilterType type) override { return type == LowPass; };
 };
+

inc/Oscillator.h

@@ -5,31 +5,41 @@
 class Oscillator {
   private:
     OscillatorType m_osc;
-    float m_freq;
+    float m_fine;
+    float m_key;
     float m_volume;
     float m_phase;
-    float m_phase_dt;
     float (Oscillator::*m_osc_function)(void);
+    void SineOscPhaseIncr();
+    void SawOscPhaseIncr();
+    float CalcSawPhaseDelta(float freq);
+    float CalcSinePhaseDelta(float freq);
+    float SawOsc();
+    float TriangleOsc();
+    float SquareOsc();
+    float Sign(float v);
+    float SineOsc();
+
+  protected:
+    float m_phase_dt;
     float (Oscillator::*m_dt_function)(float freq);
-    void sine_osc_phase_incr();
-    void saw_osc_phase_incr();
-    float calc_saw_phase_delta(float freq);
-    float calc_sine_phase_delta(float freq);
-    float sawosc();
-    float triangleosc();
-    float squareosc();
-    float sign(float v);
-    float sineosc();
 
   public:
-    Oscillator(OscillatorType osc, float freq, float volume);
+    Oscillator(OscillatorType osc, float fine, float volume);
     ~Oscillator();
     OscillatorType GetType() { return m_osc; }
     void SetType(OscillatorType osc);
     float GetVolume() { return m_volume; }
     void SetVolume(float volume) { m_volume = volume; }
-    float GetFreq() { return m_freq; }
-    void SetFreq(float freq);
+    float GetKey() { return m_key; }
+    void SetKey(float key);
+    float GetFine() { return m_fine; }
+    void SetFine(float fine) {
+        if (fine != m_fine) {
+            assert(fine >= -2.f && fine <= 2.f);
+            m_fine = fine;
+        }
+    }
     void Reset();
     float Process();
 };

inc/Synth.h

@@ -3,33 +3,34 @@
 #include "ADSR.h"
 #include "Filter.h"
 #include "Adder.h"
-#include "Effect.h"
+#include "IEffect.h"
 #include "Note.h"
 #include "Oscillator.h"
 #include "Settings.h"
 #include <vector>
+#include "LFO.h"
 
 class Synth {
   private:
     bool is_note_triggered;
     std::vector<Oscillator*> m_oscillators;
-    std::vector<Effect*> m_effects;
+    std::vector<IEffect*> m_effects;
     std::vector<float> m_out_signal;
-    Oscillator* m_lfo;
-    void zero_signal();
-    void get_note();
-    void trigger_note_on_effects();
-    void untrigger_note_on_effects();
-    void apply_effects();
-    void add_oscillator();
-    void apply_filter_lfo();
+    LFO* m_lfo;
+    void ZeroSignal();
+    void GetNote();
+    void TriggerNoteOnEffects();
+    void UntriggerNoteOnEffects();
+    void ApplyEffects();
+    void AddOscillator();
+    void ApplyFilterLfo();
   public:
     Synth(/* args */);
     ~Synth();
     void Trigger(Note input);
     void Process();
     void Release();
-    void AddEffect(Effect* fx);
+    void AddEffect(IEffect* fx);
     const std::vector<float>& GetOutSignal() { return m_out_signal; }
     const std::vector<Oscillator*>& GetOscillators() { return m_oscillators; }
     const bool& GetIsNoteTriggered() { return is_note_triggered; }

inc/SynthGuiState.h

@@ -6,7 +6,7 @@
 
 struct OscillatorGuiState {
     float volume;
-    float freq; // todo: remove or change to pitch shift
+    float fine;
     OscillatorType waveshape;
     bool is_dropdown_open;
     Rectangle shape_dropdown_rect;

src/ADSR.cpp

@@ -12,33 +12,33 @@ ADSR::ADSR(/* args */) {
 
 ADSR::~ADSR() { delete m_ramp; }
 
-bool ADSR::is_attack_elapsed() {
+bool ADSR::IsAttackElapsed() {
     return m_state == sAttack && m_ramp->IsCompleted();
 }
 
-bool ADSR::is_decay_elapsed() {
+bool ADSR::IsDecayElapsed() {
     return m_state == sDecay && m_ramp->IsCompleted();
 }
 
-bool ADSR::is_release_elapsed() {
+bool ADSR::IsReleaseElapsed() {
     return m_state == sRelease && m_ramp->IsCompleted();
 }
 
-void ADSR::recheck_state() {
+void ADSR::RecheckState() {
     switch (m_state) {
         case sAttack:
-            if (is_attack_elapsed()) {
+            if (IsAttackElapsed()) {
                 m_state = sDecay;
                 m_ramp->RampTo(m_sustain_level, m_decay_time);
             }
             break;
         case sDecay:
-            if (is_decay_elapsed()) {
+            if (IsDecayElapsed()) {
                 m_state = sSustain;
             }
             break;
         case sRelease:
-            if (is_release_elapsed()) {
+            if (IsReleaseElapsed()) {
                 m_state = sOff;
             }
             break;
@@ -47,7 +47,7 @@ void ADSR::recheck_state() {
     }
 }
 
-void ADSR::process_sample(float* sample) {
+void ADSR::ProcessSample(float* sample) {
     if (m_state == sOff) {
         (*sample) = 0;
     } else if (m_state == sAttack) {
@@ -80,8 +80,8 @@ void ADSR::Release() {
 
 void ADSR::Process(std::vector<float>& samples) {
     for (std::size_t i = 0; i < samples.size(); i++) {
-        recheck_state();
-        process_sample(&samples[i]);
+        RecheckState();
+        ProcessSample(&samples[i]);
     }
 }
 

src/Application.cpp

@@ -43,7 +43,7 @@ void Application::InitSynth() {
         assert(osc);
 
         OscillatorGuiState* ui =
-            new OscillatorGuiState{.freq = osc->GetFreq(),
+            new OscillatorGuiState{.fine = osc->GetFine(),
                                    .waveshape = osc->GetType(),
                                    .volume = osc->GetVolume()};
         m_synth_gui_state.oscillators.push_back(ui);
@@ -94,7 +94,7 @@ void Application::UpdateOnNoteInput() {
         if (!m_synth.GetIsNoteTriggered()) {
             m_synth.Trigger((*m_current_note));
         }
-        write_log("Note played: %s\n", m_current_note->name.c_str());
+        //write_log("Note played: %s\n", m_current_note->name.c_str());
     } else if (is_note_up() && m_synth.GetIsNoteTriggered()) {
         m_synth.Release();
     }

src/BandPassFilter.cpp

@@ -1,23 +1,22 @@
 #include "BandPassFilter.h"
+#include "Settings.h"
 
-BandPassFilter::BandPassFilter(/* args */) {}
-
-BandPassFilter::BandPassFilter(Filter* filter) {
-    m_freq = filter->GetFreq();
-    m_q = filter->GetRes();
-    m_order = filter->GetPeakGain();
+BandPassFilter::BandPassFilter() {
+    SetParameters(200, 0.1, 0.001);
 }
 
-BandPassFilter::BandPassFilter(float freq, float res, float q) {}
+BandPassFilter::BandPassFilter(
+    Filter* filter) {
+    SetParameters(filter->GetFreq(), filter->GetRes(), filter->GetPeakGain());
+}
+
+BandPassFilter::BandPassFilter(float freq, float res,
+                                                       float q) {
+    SetParameters(freq, res, q);
+}
 
 BandPassFilter::~BandPassFilter() {}
 
-void BandPassFilter::CalculateCoefficients() {
-    CalculateNormals();
-    m_norm = 1 / (1 + m_k / m_q + m_k * m_k);
-    m_a0 = m_k / m_q * m_norm;
-    m_a1 = 0;
-    m_a2 = -m_a0;
-    m_b1 = 2 * (m_k * m_k - 1) * m_norm;
-    m_b2 = (1 - m_k / m_q + m_k * m_k) * m_norm;
+float BandPassFilter::GetSampleForFilterType() {
+    return m_lowo;
 }

src/Filter.cpp

@@ -1,36 +1,50 @@
 #include "Filter.h"
 #include "Settings.h"
+#include <algorithm>
+#include <cmath>
 
 Filter::Filter(/* args */) {}
 
 Filter::~Filter() {}
 
-void Filter::CalculateNormals() {
-    m_v = powf(10, fabs(m_order) / 20.0);
-    m_k = tanf(M_PI * m_freq);
-}
-
 void Filter::Trigger() {}
 
 void Filter::Release() {}
 
-float Filter::Process(float in) {
-    // may move to a compile-time dictionary calculation, if needed
-    CalculateCoefficients();
-    float out = in * m_a0 + m_z1;
-    m_z1 = in * m_a1 + m_z2 - m_b1 * out;
-    m_z2 = in * m_a2 - m_b2 * out;
-    return out;
-}
-
 void Filter::Process(std::vector<float>& samples) {
     for (std::size_t i = 0; i < samples.size(); i++) {
         samples[i] = Process(samples[i]);
     }
 }
 
-void Filter::SetParameters(float freq, float res, float q) {
-    m_freq = freq / SAMPLE_RATE;
-    m_q = res;
-    m_order = q;
+
+float Filter::Process(float in) {
+    m_notcho = in - m_damp * m_bando;
+    m_lowo = m_lowo + m_freq * m_bando;
+    m_higho = m_notcho - m_lowo;
+    m_bando =
+        m_freq * m_higho + m_bando - m_drive * m_bando * m_bando * m_bando;
+    // (m_notcho or m_lowo or m_higho or m_bando or m_peako)
+    float out = 0.5 * GetSampleForFilterType();
+    m_notcho = in - m_damp * m_bando;
+    m_lowo = m_lowo + m_freq * m_bando;
+    m_higho = m_notcho - m_lowo;
+    m_bando =
+        m_freq * m_higho + m_bando - m_drive * m_bando * m_bando * m_bando;
+    out += 0.5 * GetSampleForFilterType();
+
+    return out;
+}
+
+void Filter::SetParameters(float freq, float res, float drive) {
+    m_fc = freq;
+    m_res = res;
+    m_drive = drive;
+
+    // the fs*2 is because it's double sampled
+    m_freq =
+        2.0 * std::sinf(SYNTH_PI * std::min(0.25f, m_fc / (m_fs * 2)));
+
+    m_damp = std::min(2.0f * (1.0f - std::powf(m_res, 0.25f)),
+                            std::min(2.0f, 2.0f / m_freq - m_freq * 0.5f));
 }

src/HighPassFilter.cpp

@@ -1,23 +1,22 @@
 #include "HighPassFilter.h"
+#include "Settings.h"
 
-HighPassFilter::HighPassFilter(/* args */) {}
-
-HighPassFilter::HighPassFilter(Filter* filter) {
-    m_freq = filter->GetFreq();
-    m_q = filter->GetRes();
-    m_order = filter->GetPeakGain();
+HighPassFilter::HighPassFilter() {
+    SetParameters(200, 0.1, 0.001);
 }
 
-HighPassFilter::HighPassFilter(float freq, float res, float q) {}
+HighPassFilter::HighPassFilter(
+    Filter* filter) {
+    SetParameters(filter->GetFreq(), filter->GetRes(), filter->GetPeakGain());
+}
+
+HighPassFilter::HighPassFilter(float freq, float res,
+                                                       float q) {
+    SetParameters(freq, res, q);
+}
 
 HighPassFilter::~HighPassFilter() {}
 
-void HighPassFilter::CalculateCoefficients() {
-    CalculateNormals();
-    m_norm = 1 / (1 + m_k / m_q + m_k * m_k);
-    m_a0 = 1 * m_norm;
-    m_a1 = -2 * m_a0;
-    m_a2 = m_a0;
-    m_b1 = 2 * (m_k * m_k - 1) * m_norm;
-    m_b2 = (1 - m_k / m_q + m_k * m_k) * m_norm;
+float HighPassFilter::GetSampleForFilterType() {
+    return m_higho;
 }

src/LFO.cpp

@@ -0,0 +1,10 @@
+#include "LFO.h"
+
+
+LFO::LFO(/* args */): Oscillator(Sine, 0.f, 0.5f)
+{
+}
+
+LFO::~LFO()
+{
+}

src/LowPassFilter.cpp

@@ -2,32 +2,21 @@
 #include "Settings.h"
 
 LowPassFilter::LowPassFilter() {
-    // todo: defaults
-    m_freq = 200.f / SAMPLE_RATE;
-    m_q = 1.0f;//0.707f;
-    m_order = 0;
+    SetParameters(200, 0.1, 0.001);
 }
 
-LowPassFilter::LowPassFilter(float freq, float res, float q) {
-    m_freq = freq / SAMPLE_RATE;
-    m_q = res;
-    m_order = q;
+LowPassFilter::LowPassFilter(
+    Filter* filter) {
+    SetParameters(filter->GetFreq(), filter->GetRes(), filter->GetPeakGain());
 }
 
-LowPassFilter::LowPassFilter(Filter* filter) {
-    m_freq = filter->GetFreq();
-    m_q = filter->GetRes();
-    m_order = filter->GetPeakGain();
+LowPassFilter::LowPassFilter(float freq, float res,
+                                                       float q) {
+    SetParameters(freq, res, q);
 }
 
 LowPassFilter::~LowPassFilter() {}
 
-void LowPassFilter::CalculateCoefficients() {
-    CalculateNormals();
-    m_norm = 1 / (1 + m_k / m_q + m_k * m_k);
-    m_a0 = m_k * m_k * m_norm;
-    m_a1 = 2 * m_a0;
-    m_a2 = m_a0;
-    m_b1 = 2 * (m_k * m_k - 1) * m_norm;
-    m_b2 = (1 - m_k / m_q + m_k * m_k) * m_norm;
+float LowPassFilter::GetSampleForFilterType() {
+    return m_lowo;
 }

src/Oscillator.cpp

@@ -1,11 +1,15 @@
 #include "Oscillator.h"
 #include "Settings.h"
+#include "KeyBoard.h"
+#include "Logger.h"
 
 #define TWO_PI 2 * SYNTH_PI
 
-Oscillator::Oscillator(OscillatorType osc, float freq, float volume) {
+Oscillator::Oscillator(OscillatorType osc, float fine, float volume) {
+    assert(fine >= -2.f && fine <= 2.f);
+    assert(volume >= 0.f && volume <= 1.f);
     SetType(osc);
-    m_freq = freq;
+    m_fine = fine;
     m_volume = volume;
 }
 
@@ -21,26 +25,27 @@ void Oscillator::SetType(OscillatorType osc) {
     m_osc = osc;
     switch (m_osc) {
         case Sine:
-            m_osc_function = &Oscillator::sineosc;
-            m_dt_function = &Oscillator::calc_sine_phase_delta;
+            m_osc_function = &Oscillator::SineOsc;
+            m_dt_function = &Oscillator::CalcSinePhaseDelta;
             break;
         case Triangle:
-            m_osc_function = &Oscillator::triangleosc;
-            m_dt_function = &Oscillator::calc_saw_phase_delta;
+            m_osc_function = &Oscillator::TriangleOsc;
+            m_dt_function = &Oscillator::CalcSawPhaseDelta;
             break;
         case Square:
-            m_osc_function = &Oscillator::squareosc;
-            m_dt_function = &Oscillator::calc_sine_phase_delta;
+            m_osc_function = &Oscillator::SquareOsc;
+            m_dt_function = &Oscillator::CalcSinePhaseDelta;
             break;
         case Saw:
-            m_osc_function = &Oscillator::sawosc;
-            m_dt_function = &Oscillator::calc_saw_phase_delta;
+            m_osc_function = &Oscillator::SawOsc;
+            m_dt_function = &Oscillator::CalcSawPhaseDelta;
             break;
     }
 }
 
-void Oscillator::SetFreq(float freq) {
-    m_freq = freq;
+void Oscillator::SetKey(float key) {
+    m_key = key;
+    float freq = KeyBoard::GetHzBySemitone(m_key + m_fine);
     m_phase = 0;
     m_phase_dt = (this->*m_dt_function)(freq);
 }
@@ -49,44 +54,44 @@ float Oscillator::Process() {
     return (this->*m_osc_function)() * m_volume;
 }
 
-void Oscillator::sine_osc_phase_incr() {
+void Oscillator::SineOscPhaseIncr() {
     m_phase += m_phase_dt;
     if (m_phase >= TWO_PI)
         m_phase -= TWO_PI;
 }
 
-void Oscillator::saw_osc_phase_incr() {
+void Oscillator::SawOscPhaseIncr() {
     m_phase += m_phase_dt;
     if (m_phase >= 1.0f)
         m_phase -= 1.0f;
 }
 
-float Oscillator::calc_saw_phase_delta(float freq) {
+float Oscillator::CalcSawPhaseDelta(float freq) {
     return freq / SAMPLE_RATE;
 }
 
-float Oscillator::calc_sine_phase_delta(float freq) {
+float Oscillator::CalcSinePhaseDelta(float freq) {
     return (TWO_PI * freq) / SAMPLE_RATE;
 }
 
-float Oscillator::sineosc() {
+float Oscillator::SineOsc() {
     float result = sinf(m_phase);
-    sine_osc_phase_incr();
+    SineOscPhaseIncr();
     return result;
 }
 
-float Oscillator::sign(float v) { return (v > 0.0) ? 1.f : -1.f; }
+float Oscillator::Sign(float v) { return (v > 0.0) ? 1.f : -1.f; }
 
-float Oscillator::squareosc() { return sign(sineosc()); }
+float Oscillator::SquareOsc() { return Sign(SineOsc()); }
 
-float Oscillator::triangleosc() {
+float Oscillator::TriangleOsc() {
     float result = 1.f - fabsf(m_phase - 0.5f) * 4.f;
-    saw_osc_phase_incr();
+    SawOscPhaseIncr();
     return result;
 }
 
-float Oscillator::sawosc() {
+float Oscillator::SawOsc() {
     float result = m_phase * 2.f - 1.f;
-    saw_osc_phase_incr();
+    SawOscPhaseIncr();
     return result;
 }

src/Renderer.cpp

@@ -89,7 +89,7 @@ float Renderer::draw_oscillators_panels(
 
         // Draw Oscillator Panel
         const int osc_panel_width = panel_bounds.width - 20;
-        const int osc_panel_height = has_shape_param ? 130 : 100;
+        const int osc_panel_height = has_shape_param ? 150 : 120;
         const int osc_panel_x = panel_bounds.x + 10;
         const int osc_panel_y = panel_bounds.y + 50 + panel_y_offset;
         panel_y_offset += osc_panel_height + 5;
@@ -112,13 +112,23 @@ float Renderer::draw_oscillators_panels(
         decibels =
             GuiSlider(el_rect, amp_slider_label, "", decibels, -60.0f, 0.0f);
         ui_osc->volume = powf(10.f, decibels * (1.f / 20.f));
-        osc->SetVolume(ui_osc->volume);
+        el_rect.y += el_rect.height + el_spacing;
 
+        // Fine slider
+        float fine = osc->GetFine();
+        char fine_slider_label[10];
+        snprintf(fine_slider_label, 9, "%.3f u", fine);
+        fine = GuiSlider(el_rect, fine_slider_label, "", fine, -2.f, 2.f);
+        ui_osc->fine = fine;
         el_rect.y += el_rect.height + el_spacing;
 
         // Defer shape drop-down box.
         ui_osc->shape_dropdown_rect = el_rect;
         el_rect.y += el_rect.height + el_spacing;
+
+        // Apply values to real
+        osc->SetVolume(ui_osc->volume);
+        osc->SetFine(ui_osc->fine);
     }
 
     return panel_y_offset;
@@ -191,7 +201,7 @@ void Renderer::draw_second_panel(Rectangle& bounds) {
 }
 
 float Renderer::DrawFilterPanel(Synth& synth, FilterGuiState& gui_filter,
-                                  const Rectangle& panel_bounds) {
+                                const Rectangle& panel_bounds) {
 #define FILTER_TYPE_OPTIONS "LP;BP;HP"
     Filter* filter = synth.GetFilter();
     float panel_y_offset = 0;
@@ -221,20 +231,20 @@ float Renderer::DrawFilterPanel(Synth& synth, FilterGuiState& gui_filter,
     gui_filter.freq = powf(10.f, freq);
     el_rect.y += el_rect.height + el_spacing;
 
-    //todo: implement that when Res will be fixed
-    // Resonance slider
-    // float res = gui_filter.res;
-    // char res_slider_label[32];
-    // snprintf(res_slider_label, 7, "%.1f u", res);
-    // res = GuiSlider(el_rect, res_slider_label, "", res, 0.0f, 1.0f);
-    // gui_filter.res = res;
-    // el_rect.y += el_rect.height + el_spacing;
+    // todo: implement that when Res will be fixed
+    //  Resonance slider
+    //  float res = gui_filter.res;
+    //  char res_slider_label[32];
+    //  snprintf(res_slider_label, 7, "%.1f u", res);
+    //  res = GuiSlider(el_rect, res_slider_label, "", res, 0.0f, 1.0f);
+    //  gui_filter.res = res;
+    //  el_rect.y += el_rect.height + el_spacing;
 
     // Shape select
     int shape_index = (int)(gui_filter.type);
     bool is_dropdown_click =
-        GuiDropdownBox(el_rect, FILTER_TYPE_OPTIONS,
-                        &shape_index, gui_filter.is_dropdown_open);
+        GuiDropdownBox(el_rect, FILTER_TYPE_OPTIONS, &shape_index,
+                       gui_filter.is_dropdown_open);
 
     if (is_dropdown_click) {
         write_log("Dropdown clicked!\n");
@@ -247,7 +257,12 @@ float Renderer::DrawFilterPanel(Synth& synth, FilterGuiState& gui_filter,
     // apply values to real one
     // todo: thrid (order) parameter
     // todo: why resonance changing does not work?
-    filter->SetParameters(gui_filter.freq, filter->GetRes(), filter->GetPeakGain());
+    // todo: limit filter lowest frequency  to ~40 hz
+    if (gui_filter.freq < 40.0) {
+        gui_filter.freq = 50.0;
+    }
+    filter->SetParameters(gui_filter.freq, filter->GetRes(),
+                          filter->GetPeakGain());
 
     return panel_y_offset;
 }

src/Synth.cpp

@@ -1,21 +1,23 @@
 #include "Synth.h"
+#include "FilterFactory.h"
 #include "KeyBoard.h"
 #include "Logger.h"
 #include "OscillatorType.h"
 #include "Settings.h"
-#include "FilterFactory.h"
+#include "LowPassFilter.h"
 
 Synth::Synth(/* args */) {
-    m_lfo = new Oscillator(OscillatorType::Sine, 5.f, VOLUME);
-    add_oscillator();
-    add_oscillator();
+    m_lfo = new LFO();
+    m_lfo->SetFreq(5.0);
+    AddOscillator();
+    AddOscillator();
     AddEffect(new ADSR());
     AddEffect(FilterFactory::GetDefaultFilter());
     for (size_t i = 0; i < STREAM_BUFFER_SIZE; i++) {
         float sample = 0.0f;
         m_out_signal.push_back(sample);
     }
-    zero_signal();
+    ZeroSignal();
 }
 
 Synth::~Synth() {
@@ -24,80 +26,80 @@ Synth::~Synth() {
     m_out_signal.clear();
 }
 
-void Synth::zero_signal() {
+void Synth::ZeroSignal() {
     float sample = 0.0f;
     for (size_t i = 0; i < STREAM_BUFFER_SIZE; i++) {
         m_out_signal[i] = sample;
     }
 }
 
-void Synth::get_note() {
-    zero_signal();
+void Synth::GetNote() {
+    ZeroSignal();
     Adder::SumOscillators(m_oscillators, m_out_signal);
 }
 
-void Synth::apply_effects() {
-    for (Effect* effect : m_effects) {
-        effect->Process(m_out_signal);
+void Synth::ApplyEffects() {
+    auto* adsr = m_effects[0];
+    adsr->Process(m_out_signal);
+
+    Filter* filter = (Filter*)m_effects[1];
+
+    for (std::size_t i = 0; i < m_out_signal.size(); i++) {
+        ApplyFilterLfo();
+        m_out_signal[i] = filter->Process(m_out_signal[i]);
     }
 }
 
-void Synth::trigger_note_on_effects() {
-    for (Effect* effect : m_effects) {
+void Synth::TriggerNoteOnEffects() {
+    for (IEffect* effect : m_effects) {
         effect->Trigger();
     }
 }
 
-void Synth::untrigger_note_on_effects() {
-    for (Effect* effect : m_effects) {
+void Synth::UntriggerNoteOnEffects() {
+    for (IEffect* effect : m_effects) {
         effect->Release();
     }
 }
 
-void Synth::add_oscillator() {
-    m_oscillators.push_back(
-        new Oscillator(OscillatorType::Sine, 440.f, VOLUME));
+void Synth::AddOscillator() {
+    m_oscillators.push_back(new Oscillator(OscillatorType::Sine, 0.0f, VOLUME));
 }
 
 void Synth::Trigger(Note input) {
     int semitone_shift = KeyBoard::GetSemitoneShift(input.name);
-    float hz = KeyBoard::GetHzBySemitone(semitone_shift);
 
     for (Oscillator* osc : m_oscillators) {
-        osc->SetFreq(hz);
+        osc->SetKey(semitone_shift);
     }
     is_note_triggered = true;
-    trigger_note_on_effects();
+    TriggerNoteOnEffects();
 }
 
-// todo: fix this
-void Synth::apply_filter_lfo() {
+void Synth::ApplyFilterLfo() {
     float dt = m_lfo->Process();
     Filter* filter = (Filter*)m_effects[1];
     float freq = filter->GetFreq();
-    //todo: check formula
-    //filter->SetParameters(freq + dt * 0.2f, filter->GetRes(), filter->GetPeakGain());
+    filter->SetParameters(freq + dt, filter->GetRes(), filter->GetPeakGain());
 }
 
 void Synth::Process() {
-    //todo: on each sample. 
-    //in order to do that, we need to move to per-sample processing
-    apply_filter_lfo();
-    get_note();
-    apply_effects();
+    GetNote();
+    ApplyEffects();
 }
 
 void Synth::Release() {
-    zero_signal();
+    ZeroSignal();
     is_note_triggered = false;
-    untrigger_note_on_effects();
+    UntriggerNoteOnEffects();
 }
 
-void Synth::AddEffect(Effect* fx) { m_effects.push_back(fx); }
+void Synth::AddEffect(IEffect* fx) { m_effects.push_back(fx); }
 
 void Synth::SetFilter(FilterType type) {
     Filter* old_filter = this->GetFilter();
     if (!old_filter->IsSameFilterType(type)) {
+        // todo: implement other types of state variable filters;
         Filter* new_filter = FilterFactory::CreateFilter(old_filter, type);
         delete old_filter;
         m_effects[1] = new_filter;