Starting on Frequency Shifter module

src/CMakeLists.txt

@@ -132,6 +132,7 @@ target_sources(BYOD PRIVATE
     processors/other/Compressor.cpp
     processors/other/Delay.cpp
     processors/other/EnvelopeFilter.cpp
+    processors/other/FrequencyShifter.cpp
     processors/other/LevelDetective.cpp
     processors/other/Gate.cpp
     processors/other/Octaver.cpp

src/processors/ProcessorStore.cpp

@@ -53,6 +53,7 @@
 #include "other/Compressor.h"
 #include "other/Delay.h"
 #include "other/EnvelopeFilter.h"
+#include "other/FrequencyShifter.h"
 #include "other/Gate.h"
 #include "other/LevelDetective.h"
 #include "other/Octaver.h"
@@ -148,6 +149,7 @@ ProcessorStore::StoreMap ProcessorStore::store = {
     { "Crying Child", { &processorFactory<CryBaby>, { ProcessorType::Other, CryBaby::numInputs, CryBaby::numOutputs } } },
     { "Delay", { &processorFactory<DelayModule>, { ProcessorType::Other, 1, 1 } } },
     { "Envelope Filter", { &processorFactory<EnvelopeFilter>, { ProcessorType::Other, EnvelopeFilter::numInputs, EnvelopeFilter::numOutputs } } },
+    { "Frequency Shifter", { &processorFactory<FrequencyShifter>, { ProcessorType::Other, 1, 1 } } },
     { "Level Detective", { &processorFactory<LevelDetective>, { ProcessorType::Other, 1, 1 } } },
     { "Gate", { &processorFactory<Gate>, { ProcessorType::Other, 1, 1 } } },
     { "Octaver", { &processorFactory<Octaver>, { ProcessorType::Other, 1, 1 } } },

src/processors/other/FrequencyShifter.cpp

@@ -0,0 +1,48 @@
+#include "FrequencyShifter.h"
+#include "processors/ParameterHelpers.h"
+
+FrequencyShifter::FrequencyShifter (UndoManager* um)
+    : BaseProcessor ("Frequency Shifter", createParameterLayout(), um)
+{
+    using namespace ParameterHelpers;
+    loadParameterPointer (shiftParam, vts, "shift");
+
+    uiOptions.backgroundColour = Colours::palevioletred.brighter (0.1f);
+    uiOptions.powerColour = Colours::yellow;
+    uiOptions.info.description = "A frequency shifter effect.";
+    uiOptions.info.authors = StringArray { "Jatin Chowdhury" };
+}
+
+ParamLayout FrequencyShifter::createParameterLayout()
+{
+    using namespace ParameterHelpers;
+    auto params = createBaseParams();
+
+    createFreqParameter (params, "shift", "Shift", 0.0f, 200.0f, 20.0f, 20.0f);
+
+    return { params.begin(), params.end() };
+}
+
+void FrequencyShifter::prepare (double sampleRate, int samplesPerBlock)
+{
+    hilbertFilter.reset();
+    modulator.prepare ({ sampleRate, (uint32_t) samplesPerBlock,  1});
+}
+
+void FrequencyShifter::processAudio (AudioBuffer<float>& buffer)
+{
+    modulator.setFrequency (shiftParam->getCurrentValue());
+
+    for (auto [ch, data] : chowdsp::buffer_iters::channels (buffer))
+    {
+        for (auto& x : data)
+        {
+            const auto [x_re, x_im] = hilbertFilter.process (x);
+            const auto [mod_sin, mod_cos] = modulator.processSampleQuadrature();
+
+            x = x_re * mod_sin - x_im * mod_cos;
+        }
+    }
+
+    // TODO: DC blocker
+}

src/processors/other/FrequencyShifter.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "../BaseProcessor.h"
+
+class FrequencyShifter : public BaseProcessor
+{
+public:
+    explicit FrequencyShifter (UndoManager* um = nullptr);
+
+    ProcessorType getProcessorType() const override { return Other; }
+    static ParamLayout createParameterLayout();
+
+    void prepare (double sampleRate, int samplesPerBlock) override;
+    void processAudio (AudioBuffer<float>& buffer) override;
+
+private:
+    chowdsp::FloatParameter* shiftParam = nullptr;
+
+    chowdsp::HilbertFilter<float> hilbertFilter;
+    chowdsp::SineWave<float> modulator {};
+
+    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (FrequencyShifter)
+};