WaveShaper.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
 
namespace Audio
{
    enum class EWaveShaperType : int32
    {
        Sin,
        ATan,
        Tanh,
        Cubic,
        HardClip
    };
 
    // A digital wave shaping effect to cause audio distortion
    // https://en.wikipedia.org/wiki/Waveshaper
    class FWaveShaper
    {
    public:
        // Constructor
        SIGNALPROCESSING_API FWaveShaper();
 
        // Destructor
        SIGNALPROCESSING_API ~FWaveShaper();
 
        // Initialize the equalizer
        SIGNALPROCESSING_API void Init(const float InSampleRate);
 
        // Sets the amount of wave shapping. 0.0 is no effect.
        SIGNALPROCESSING_API void SetAmount(const float InAmount);
 
        // Set DC offset before processing
        SIGNALPROCESSING_API void SetBias(const float InBias);
 
        // Sets the output gain of the waveshaper
        SIGNALPROCESSING_API void SetOutputGainDb(const float InGainDb);
 
        // Sets the output gain of the waveshaper
        SIGNALPROCESSING_API void SetOutputGainLinear(const float InGainLinear);
 
        SIGNALPROCESSING_API void SetType(const EWaveShaperType InType);
 
        // Processes one Sample, using ATan
        // Deprecating in favor of ProcessAudioBuffer
        SIGNALPROCESSING_API void ProcessAudio(const float InSample, float& OutSample);
 
        // Process an entire buffer of audio
        SIGNALPROCESSING_API void ProcessAudioBuffer(const float* InBuffer, float* OutBuffer, int32 NumFrames);
 
    private:
 
        float Amount;
        float OutputGain;
        float Bias;
        EWaveShaperType Type;
 
        float OneOverAtanAmount;
        float OneOverTanhAmount;
 
        void ProcessHardClip(const float* InBuffer, float* OutBuffer, int32 NumSamples);
        void ProcessTanh(const float* InBuffer, float* OutBuffer, int32 NumSamples);
        void ProcessATan(const float* InBuffer, float* OutBuffer, int32 NumSamples);
        void ProcessCubic(const float* InBuffer, float* OutBuffer, int32 NumSamples);
        void ProcessSin(const float* InBuffer, float* OutBuffer, int32 NumSamples);
    };
 
}