AllPassFractionalDelay.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "BufferVectorOperations.h"
#include "AlignedBlockBuffer.h"
 
namespace Audio
{
    // Performs a fractional delay utilzing a single order all pass filter.
    class FAllPassFractionalDelay
    {
    public:
        // InMaxDelay sets the maximum allowable delay that this object can support. The minimum delay is 0.5
        // InNumInternalBufferSamples sets the maximum block processing size.
        SIGNALPROCESSING_API FAllPassFractionalDelay(int32 InMaxDelay, int32 InNumInternalBufferSamples);
 
        SIGNALPROCESSING_API ~FAllPassFractionalDelay();
 
        // Apply delay to InSamples. Fill OutSamples with data from the delay line at a delay of InDelay.
        // InDelay must be equal length to InSamples. 
        SIGNALPROCESSING_API void ProcessAudio(const FAlignedFloatBuffer& InSamples, const FAlignedFloatBuffer& InDelays, FAlignedFloatBuffer& OutSamples);
 
        // Set all values in internal delay line to zero. 
        SIGNALPROCESSING_API void Reset();
 
    private:
        void ProcessAudioBlock(const float* InSamples, const float* InDelays, const int32 InNum, float* OutSamples);
 
        int32 MaxDelay;
        int32 NumInternalBufferSamples;
 
        // Delay element for all pass filter.
        float Z1;
 
        TUniquePtr<FAlignedBlockBuffer> DelayLine;
 
        FAlignedFloatBuffer Coefficients;
        FAlignedFloatBuffer FractionalDelays;
        FAlignedInt32Buffer IntegerDelays;
        FAlignedInt32Buffer IntegerDelayOffsets;
    };
}