InterpolatedLinearPitchShifter.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "DSP/Dsp.h"
#include "DSP/ParamInterpolator.h"
 
namespace Audio
{
    class FLinearPitchShifter
    {
    public:
        // ctor
        SIGNALPROCESSING_API FLinearPitchShifter(int32 InNumChannels = 0);
 
        SIGNALPROCESSING_API void Reset(int32 InNumChannels, float InInitialPitchShiftSemitones = 0.0f, int32 InInterpLengthFrames = 100);
 
        // Sample rate converts the input audio buffer and pushes converted audio to the output circular buffer.
        // (Returns the number of output frames generated.)
        SIGNALPROCESSING_API int32 ProcessAudio(const TArrayView<float> InputBuffer, Audio::TCircularAudioBuffer<float>& OutputBuffer);
 
        SIGNALPROCESSING_API void UpdatePitchShift(float InNewPitchSemitones);
 
    private:
        // returns next fractional index increment
        float GetNextIndexDelta();
 
        TArray<float> PreviousFrame;
        FParam PitchShiftRatio;
        float CurrentIndex{ 0.0f };
        int32 NumChannels{ 0 };
        int32 InterpLengthFrames{ 100 };
        int32 InterpFramesRemaining{ 0 };
 
    }; // class FLinearPitchShifter
} // namespace Audio