Phaser.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "DSP/Delay.h"
#include "DSP/LFO.h"
#include "DSP/Filter.h"
 
namespace Audio
{
 
    class FPhaser
    {
    public:
        SIGNALPROCESSING_API FPhaser();
        SIGNALPROCESSING_API ~FPhaser();
 
        SIGNALPROCESSING_API void Init(const float SampleRate, const int32 InNumChannels);
 
        // Sets the phaser LFO rate
        SIGNALPROCESSING_API void SetFrequency(const float InFreqHz);
 
        // Sets the wet level of the phaser
        SIGNALPROCESSING_API void SetWetLevel(const float InWetLevel);
 
        // Sets the feedback of the phaser
        SIGNALPROCESSING_API void SetFeedback(const float InFeedback);
 
        // Sets the phaser LFO type
        SIGNALPROCESSING_API void SetLFOType(const ELFO::Type LFOType);
 
        // Sets whether or not to put the phaser in quadrature mode
        SIGNALPROCESSING_API void SetQuadPhase(const bool bQuadPhase);
 
        // Process an audio frame
        SIGNALPROCESSING_API void ProcessAudioFrame(const float* InFrame, float* OutFrame);
 
        // Process an audio buffer.
        SIGNALPROCESSING_API void ProcessAudio(const float* InBuffer, const int32 InNumSamples, float* OutBuffer);
 
    protected:
        SIGNALPROCESSING_API void ComputeNewCoefficients(const int32 ChannelIndex, const float LFOValue);
 
        // First-order all-pass filters in series
        static const int32 NumApfs = 6;
        static const int32 MaxNumChannels = 2;
 
        int32 ControlSampleCount;
        int32 ControlRate;
        float Frequency;
        float WetLevel;
        float Feedback;
        ELFO::Type LFOType;
 
        // 6 APFs per channel
        FBiquadFilter APFs[MaxNumChannels][NumApfs];
        FVector2D APFFrequencyRanges[NumApfs];
 
        // Feedback samples
        float FeedbackFrame[MaxNumChannels];
 
        FLFO LFO;
 
        // Number of channels actually used
        int32 NumChannels;
 
        bool bIsBiquadPhase;
    };
 
}