87 lines
3.7 KiB
C++
87 lines
3.7 KiB
C++
// Copyright Epic Games, Inc. All Rights Reserved.
|
|
|
|
#pragma once
|
|
|
|
#include "CoreMinimal.h"
|
|
#include "Misc/CoreMiscDefines.h"
|
|
#include "DSP/BufferVectorOperations.h"
|
|
#include "DSP/Dsp.h"
|
|
#include "DSP/FFTAlgorithm.h"
|
|
|
|
namespace Audio
|
|
{
|
|
// Types of spectrums which can be directly derived from FFTFreqDomainData
|
|
|
|
enum class ESpectrumType : uint8
|
|
{
|
|
MagnitudeSpectrum,
|
|
PowerSpectrum
|
|
};
|
|
|
|
|
|
enum class EWindowType : uint8
|
|
{
|
|
None, // No window is applied. Technically a boxcar window.
|
|
Hamming, // Mainlobe width of -3 dB and sidelove attenuation of ~-40 dB. Good for COLA.
|
|
Hann, // Mainlobe width of -3 dB and sidelobe attenuation of ~-30dB. Good for COLA.
|
|
Blackman // Mainlobe width of -3 dB and sidelobe attenuation of ~-60db. Tricky for COLA.
|
|
};
|
|
|
|
// Utility functions for generating different types of windows. Called in FWindow::Generate.
|
|
SIGNALPROCESSING_API void GenerateRectangularWindow(float* WindowBuffer, int32 NumFrames, int32 NumChannels);
|
|
SIGNALPROCESSING_API void GenerateHammingWindow(float* WindowBuffer, int32 NumFrames, int32 NumChannels, bool bIsPeriodic);
|
|
SIGNALPROCESSING_API void GenerateHannWindow(float* WindowBuffer, int32 NumFrames, int32 NumChannels, bool bIsPeriodic);
|
|
SIGNALPROCESSING_API void GenerateBlackmanWindow(float* WindowBuffer, int32 NumFrames, int32 NumChannels, bool bIsPeriodic);
|
|
SIGNALPROCESSING_API void GenerateWindow(float* InOutWindowBuffer, EWindowType InType, int32 InNumFrames, int32 InNumChannels, bool bIsPeriodic);
|
|
|
|
// Returns the hop size in samples necessary to maintain constant overlap add.
|
|
// For more information on COLA, see the following page:
|
|
// https://ccrma.stanford.edu/~jos/sasp/Overlap_Add_OLA_STFT_Processing.html
|
|
SIGNALPROCESSING_API uint32 GetCOLAHopSizeForWindow(EWindowType InType, uint32 WindowLength);
|
|
|
|
/**
|
|
* Class used to generate, contain and apply a DSP window of a given type.
|
|
*/
|
|
class FWindow
|
|
{
|
|
public:
|
|
FWindow() = delete;
|
|
|
|
/**
|
|
* Constructor. Allocates buffer and generates window inside of it.
|
|
* @param InType: The type of window that should be generated.
|
|
* @param InNumFrames: The number of samples that should be generated divided by the number of channels.
|
|
* @param InNumChannels: The amount of channels that will be used in the signal this is applied to.
|
|
* @param bIsPeriodic: If false, the window will be symmetrical. If true, the window will be periodic.
|
|
* Generally, set this to false if using this window with an STFT, but use true
|
|
* if this window will be used on an entire, self-contained signal.
|
|
*/
|
|
SIGNALPROCESSING_API FWindow(EWindowType InType, int32 InNumFrames, int32 InNumChannels, bool bIsPeriodic);
|
|
|
|
// Apply this window to InBuffer, which is expected to be an interleaved buffer with the same amount of frames
|
|
// and channels this window was constructed with.
|
|
SIGNALPROCESSING_API void ApplyToBuffer(float* InBuffer);
|
|
|
|
SIGNALPROCESSING_API EWindowType GetWindowType() const;
|
|
|
|
private:
|
|
EWindowType WindowType;
|
|
FAlignedFloatBuffer WindowBuffer;
|
|
int32 NumSamples;
|
|
|
|
// Generate the window. Called on constructor.
|
|
SIGNALPROCESSING_API void Generate(int32 NumFrames, int32 NumChannels, bool bIsPeriodic);
|
|
};
|
|
|
|
// Return the ceiling of the log2 of InNum
|
|
SIGNALPROCESSING_API int32 CeilLog2(int32 InNum);
|
|
|
|
// Return the scaling factor needed to apply to a power spectrum given a current
|
|
// and target FFT scaling.
|
|
SIGNALPROCESSING_API float GetPowerSpectrumScaling(int32 FFTSize, EFFTScaling InCurrentScaling, EFFTScaling InTargetScaling);
|
|
|
|
// Scale the power spectrum to remove any scaling introduced by the FFT algorithm
|
|
// implementation.
|
|
SIGNALPROCESSING_API void ScalePowerSpectrumInPlace(int32 FFTSize, EFFTScaling InCurrentScaling, EFFTScaling InTargetScaling, TArrayView<float> InPowerSpectrum);
|
|
}
|