IntegerDelay.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "DSP/Dsp.h"
#include "DSP/AlignedBlockBuffer.h"
#include "DSP/BufferVectorOperations.h"
 
namespace Audio
{
 
    // An adjustable delay line. Delays values are limited to integer values. 
    class FIntegerDelay
    {
    public:
 
        // InMaxDelaySamples is the maximum supported delay.
        // InDelaySamples is the initial delay in samples.
        SIGNALPROCESSING_API FIntegerDelay(int32 InMaxNumDelaySamples, int32 InNumDelaySamples, int32 InNumInternalBufferSamples = 256);
 
        // Destructor
        SIGNALPROCESSING_API ~FIntegerDelay();
 
        // Sets the current delay in samples. InDelay must be less than or equal to the InMaxDelaySamples set in the constructor.
        SIGNALPROCESSING_API void SetDelayLengthSamples(int32 InNumDelaySamples);
 
        // Resets the delay line state, flushes buffer and resets read/write pointers.
        SIGNALPROCESSING_API void Reset();
 
        // Returns the current delay length in samples.
        SIGNALPROCESSING_API int32 GetNumDelaySamples() const;
 
        // Process InSamples, placing delayed versions in OutSamples.
        inline float ProcessAudioSample(float InSample)
        {
            // Update delay line.   
            DelayLine->AddSamples(&InSample, 1);
 
            // Copy delayed version to output
            const float DelayedSample = *(DelayLine->InspectSamples(1 + NumBufferOffsetSamples, NumDelayLineOffsetSamples));
 
            // Remove unneeded delay line.
            DelayLine->RemoveSamples(1);
 
            return DelayedSample;
        }
 
        SIGNALPROCESSING_API void ProcessAudio(const Audio::FAlignedFloatBuffer& InSamples, Audio::FAlignedFloatBuffer& OutSamples);
        // Process InSamples, placing delayed versions in OutSamples.
        SIGNALPROCESSING_API void ProcessAudio(TArrayView<const float> InSamples, TArrayView<float> OutSamples);
 
        // Retrieve a copy of the internal delay line.
        // InNum must be less than or equal to InMaxNumDelaySamples.
        SIGNALPROCESSING_API void PeekDelayLine(int32 InNum, Audio::FAlignedFloatBuffer& OutSamples);
 
    private:
        // Process a block of audio. InNum is always less than or equal to NumInternalBufferSamples.
        void ProcessAudioBlock(const float* InSamples, const int32 InNum, float* OutSamples);
 
        // Maximum supported number of delay samples
        int32 MaxNumDelaySamples;
 
        // Current number of delay samples
        int32 NumDelaySamples;
 
        // Offset of output delayed samples relative to DelayLine block buffer
        int32 NumDelayLineOffsetSamples;
 
        // Offset to handle delay values which are not multiple of required buffer alignment.
        int32 NumBufferOffsetSamples;
 
        // Number of samples in an internal buffer
        int32 NumInternalBufferSamples;
 
        // Buffer for holding delayed data.
        TUniquePtr<FAlignedBlockBuffer> DelayLine;
    };
}