Flanger.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "DSP/BufferVectorOperations.h"
#include "DSP/Delay.h"
 
namespace Audio
{
    class FFlanger
    {
    public: 
        SIGNALPROCESSING_API FFlanger();
        SIGNALPROCESSING_API ~FFlanger();
 
        SIGNALPROCESSING_API void Init(const float InSampleRate);
 
        SIGNALPROCESSING_API void SetModulationRate(const float InModulationRate);
        SIGNALPROCESSING_API void SetModulationDepth(const float InModulationDepth);
        SIGNALPROCESSING_API void SetCenterDelay(const float InCenterDelay);
        SIGNALPROCESSING_API void SetMixLevel(const float InMixLevel);
 
        SIGNALPROCESSING_API void ProcessAudio(const FAlignedFloatBuffer& InBuffer, const int32 InNumSamples, FAlignedFloatBuffer& OutBuffer);
    protected: 
        static SIGNALPROCESSING_API const float MaxDelaySec;
        static SIGNALPROCESSING_API const float MaxModulationRate;
        static SIGNALPROCESSING_API const float MaxCenterDelay;
 
        // LFO parameters
        // LFO frequency 
        float ModulationRate = 0.5f;
        // Modulation depth is clamped to CenterDelayMsec to avoid clipping
        float ModulationDepth = 0.5f;
        float CenterDelayMsec = 0.5f;
 
        // Balance between original and delayed signal 
        // (Should be between 0 and 1.0; 
        // 0.5 is equal amounts of each and 
        // > 0.5 is more delayed signal than non-delayed signal)
        float MixLevel = 0.5f;
        float DelayedSignalLevel = 0.5f;
        float NonDelayedSignalLevel = 0.5f;
 
        // Internal delay buffer 
        FDelay DelayBuffer;
        // Scratch buffer used for accumulating delay samples per block
        FAlignedFloatBuffer ScratchBuffer;
 
        // Delay sample generated from LFO per block
        float DelaySample = 0.0f;
 
        // Internal LFO for delay amount
        FSinOsc2DRotation LFO;
 
        // The audio sample rate, Init() must be called to initialize this
        float SampleRate = 48000.0f;
    };
}