UnrealEngineUWP/Engine/Source/Runtime/SignalProcessing/Private/IntegerDelay.cpp

// Copyright Epic Games, Inc. All Rights Reserved.

#include "DSP/IntegerDelay.h"
#include "DSP/BufferVectorOperations.h"

using namespace Audio;

FIntegerDelay::FIntegerDelay(int32 InMaxNumDelaySamplesSamples, int32 InNumDelaySamples, int32 InNumInternalBufferSamples)
:	MaxNumDelaySamples(InMaxNumDelaySamplesSamples)
	, NumDelaySamples(0)
	, NumDelayLineOffsetSamples(0)
	, NumBufferOffsetSamples(0)
	, NumInternalBufferSamples(InNumInternalBufferSamples)
{
	// Allocate and prepare delay line for maximum delay.
	DelayLine = MakeUnique<FAlignedBlockBuffer>((2 * MaxNumDelaySamples) + NumInternalBufferSamples, MaxNumDelaySamples + NumInternalBufferSamples);
	DelayLine->AddZeros(MaxNumDelaySamples);

	// Set current delay.
	SetDelayLengthSamples(InNumDelaySamples);
}


// Destructor
FIntegerDelay::~FIntegerDelay()
{}

void FIntegerDelay::SetDelayLengthSamples(int32 InNumDelaySamples)
{
	checkf(InNumDelaySamples <= MaxNumDelaySamples, TEXT("InNumDelaySamples must be less than or equal to MaxNumDelaySamples"));
	checkf(InNumDelaySamples >= 0, TEXT("InNumDelaySamples must be greater than or equal to 0"));

	if (InNumDelaySamples > MaxNumDelaySamples)
	{
		InNumDelaySamples = MaxNumDelaySamples;
	}
	else if (InNumDelaySamples < 0)
	{
		InNumDelaySamples = 0;
	}

	NumDelaySamples = InNumDelaySamples;
	// Store offset location for reading samples out from delay line.
	// We keep a couple offsets around to ensure we do go over buffer bounds
	// and abide by alignment rules of FAlignedBlockBuffer
	NumDelayLineOffsetSamples = MaxNumDelaySamples - NumDelaySamples;
	NumBufferOffsetSamples = 0;
	while (0 != (NumDelayLineOffsetSamples % AUDIO_NUM_FLOATS_PER_VECTOR_REGISTER))
	{
		NumDelayLineOffsetSamples--;
		NumBufferOffsetSamples++;
	}
}

// Resets the delay line state, flushes buffer and resets read/write pointers.
void FIntegerDelay::Reset() 
{
	DelayLine->ClearSamples();
	DelayLine->AddZeros(MaxNumDelaySamples);
}

// Returns the current delay line length (in samples).
int32 FIntegerDelay::GetNumDelaySamples() const 
{
	return NumDelaySamples;
}

void FIntegerDelay::ProcessAudio(const Audio::FAlignedFloatBuffer& InSamples, Audio::FAlignedFloatBuffer& OutSamples)
{
	const float* InSampleData = InSamples.GetData();
	const int32 InNum = InSamples.Num();

	// Prepare output buffer
	OutSamples.Reset(InNum);
	OutSamples.AddUninitialized(InNum);
	float* OutSampleData = OutSamples.GetData();

	// Process audio one block at a time.
	int32 LeftOver = InNum;
	int32 BufferPos = 0;
	while (LeftOver > 0)
	{
		int32 NumToProcess = FMath::Min(LeftOver, NumInternalBufferSamples);
		ProcessAudioBlock(&InSampleData[BufferPos], NumToProcess, &OutSampleData[BufferPos]);
		BufferPos += NumToProcess;
		LeftOver -= NumToProcess;
	}
}

void FIntegerDelay::ProcessAudioBlock(const float* InSamples, const int32 InNum, float* OutSamples)
{
	
	// Update delay line.	
	DelayLine->AddSamples(InSamples, InNum);

	// Copy delayed version to output
	const float* DelayData = DelayLine->InspectSamples(InNum + NumBufferOffsetSamples, NumDelayLineOffsetSamples);

	FMemory::Memcpy(OutSamples, &DelayData[NumBufferOffsetSamples], InNum * sizeof(float));
	
	// Remove unneeded delay line.
	DelayLine->RemoveSamples(InNum);
}

void FIntegerDelay::PeekDelayLine(int32 InNum, Audio::FAlignedFloatBuffer& OutSamples)
{
	int32 NumToInspect = FMath::Min(DelayLine->GetNumAvailable(), NumDelaySamples);
	NumToInspect = FMath::Min(InNum, NumToInspect);

	const float* DelaySamples = DelayLine->InspectSamples(NumToInspect);
	if (nullptr == DelaySamples)
	{
		OutSamples.Reset(0);
		return;
	}

	OutSamples.Reset(NumToInspect);
	OutSamples.AddUninitialized(NumToInspect);
	FMemory::Memcpy(OutSamples.GetData(), DelaySamples, NumToInspect * sizeof(float));
}