BitCrusher.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "DSP/Osc.h"
 
namespace Audio
{
    // Bit crushing effect
    // https://en.wikipedia.org/wiki/Bitcrusher
    class FBitCrusher
    {
    public:
        // Constructor
        SIGNALPROCESSING_API FBitCrusher();
 
        // Destructor
        SIGNALPROCESSING_API ~FBitCrusher();
 
        // Initialize the equalizer
        SIGNALPROCESSING_API void Init(const float InSampleRate, const int32 InNumChannels);
 
        // The amount to reduce the sample rate of the audio stream.
        SIGNALPROCESSING_API void SetSampleRateCrush(const float InFrequency);
 
        // The amount to reduce the bit depth of the audio stream.
        SIGNALPROCESSING_API void SetBitDepthCrush(const float InBitDepth);
 
        // Processes audio
        SIGNALPROCESSING_API void ProcessAudioFrame(const float* InFrame, float* OutFrame);
        SIGNALPROCESSING_API void ProcessAudio(const float* InBuffer, const int32 InNumSamples, float* OutBuffer);
 
        // Returns the maximum value given bit depths will be clamped to.
        static SIGNALPROCESSING_API float GetMaxBitDepth();
 
    private:
        // i.e. 8 bit, etc. But can be float!
        float SampleRate;
        float BitDepth;
        float BitDelta;
        float ReciprocalBitDelta;
 
        // The current phase of the bit crusher
        float Phase;
 
        // The amount of phase to increment each sample
        float PhaseDelta;
 
        // Used to sample+hold the last output
        float LastOutput[2];
 
        int32 NumChannels;
    };
 
}