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API > API/Runtime > API/Runtime/SignalProcessing

Filters

Classes

  Type Name Description
Public class FAcousticEchoCancellation    
Public class FAcousticEchoCancellation_DEPRECATED This class uses an adaptive filter to cancel out any rendered audio signal that might be picked up by the mic.  
Public class FAdaptiveFilter    
Public class FAdaptiveFilter_DEPRECATED VoiceProcessing.h Deprecation  
Public class FADEnvelope Sample accurate attack-decay style envelope generator  
Public class FAlignedBlockBuffer First In First Out Buffer designed for audio buffers.  
Public class FAllPassFractionalDelay Performs a fractional delay utilzing a single order all pass filter.  
Public class FAmp Class which manages scaling audio input and performing panning operations.  
Public class FAsyncSpectrumAnalyzer SpectrumAnalyzer for computing spectrum in async task.  
Public class FAsyncSpectrumAnalyzerScopeLock    
Public class FAttackRelease Conversion between attack/release time and attack/release sample counts.  
Public class FAttackReleaseSmoother Smooths signals using attack and release settings.  
Public struct FAudioBufferDistanceAttenuationSettings Settings for audio buffer distance attenuation.  
Public class FAudioFFTAlgorithmFactory FFT Algorithm factory for this FFT implementation  
Public class FAudioFileWriter    
Public class FBaseChannelFormatConverter FBaseChannelFormatConverter implements channel conversion using a simple mixing matrix.  
Public class FBiquad Simple biquad filter structure handling a biquad formulation See: https://en.wikipedia.org/wiki/Digital_biquad_filter Calculations of coefficients are handled outside this class.  
Public class FBiquadFilter Biquad filter class which wraps a biquad filter struct Handles multi-channel audio to avoid calculating filter coefficients for multiple channels of audio.  
Public class FBitCrusher Bit crushing effect https://en.wikipedia.org/wiki/Bitcrusher  
Public class FBlockCorrelator Correlation calculator which utilizes FFT to perform fast correlation calculations.  
Public struct FBlockCorrelatorSettings Settings for block correlator  
Public class FBufferLinearEase Class which handles a vectorized interpolation of an entire buffer to the values of a target buffer  
Public class FBufferOnePoleLPF Simple 1-pole lowpass filter.  
Public struct FChannelMapParams Parameters for creating 2D channel maps.  
Public class FChorus    
Public class FContiguousSparse2DKernelTransform FContiguousSparse2DKernelTransform  
Public struct FConvertDeinterleaveParams Parameters for creating a IConvertDeinterleave object.  
Public class FConvolutionFactory FConvolutionFactory  
Public struct FConvolutionSettings FConvolutionSettings  
Public class FDelay Circular Buffer Delay Line.  
Public class FDelayAPF Implementation of a delay line with a feedback/feedforward gain coefficient APF filters pass all frequencies but changes phase relationships of frequencies  
Public class FDelayStereo    
Public struct FDirectedGraphAlgo    
Public struct FDirectedTreeElement An element in a directed tree with references to children of a vertex.  
Public class FDynamicDelayAPF All Pass Filter with a long fractional delay which can be set per a sample.  
Public class FDynamicsProcessor Dynamic range compressor https://en.wikipedia.org/wiki/Dynamic_range_compression  
Public class FDynamicStateVariableFilter Combination of two state-variable filters, the first filtering a key signal, which drives gain in the second  
Public class FEarlyReflections Basic implementation of a 4x4 Feedback Delay Network.  
Public class FEarlyReflectionsFast Basic implementation of early reflections using a predelay, low pass filter and feedback delay network (FDN).  
Public struct FEarlyReflectionsFastSettings    
Public struct FEarlyReflectionsSettings    
Public class FEnvelope Envelope class generates ADSR style envelope.  
Public class FEnvelopeFollower A simple utility that returns a smoothed value given audio input using an RC circuit.  
Public struct FEnvelopeFollowerInitParams    
Public class FEqualizer Equalizer filter An equalizer is a cascaded (serial) band of parametric EQs This filter allows for setting each band with variable Bandwidth/Q, Frequency, and Gain  
Public struct FEventQuantizationSettings    
Public class FEventQuantizer Class which handles the details of event quantization.  
Public class FExponentialEase Simple exponential easing class. Useful for cheaply and smoothly interpolating parameters.  
Public class FFDAPFilterComputer    
Public class FFDAPFilterComputer_DEPRECATED This class takes an incoming signal and an outgoing signal, Correlates them, and returns the frequency values of the weight targets to pass to an adaptive filter.  
Public struct FFDNCoefficients Filter coefficients of 4 channel feedback delay network.  
Public struct FFDNDelaySettings Delay settings of 4 channel feedback delay network.  
Public class FFeedbackDelayNetwork 4 channel feedback delay network (FDN) for artificial reverberation.  
Public class FFFTConvolver_DEPRECATED Deprecated in 5.1.  
Public class FFFTFactory FFFTFactory  
Public struct FFFTSettings FFFTSettings  
Public class FFlanger    
Public class FFoldbackDistortion Foldback distortion effect https://en.wikipedia.org/wiki/Foldback_(power_supply_design)  
Public struct FFTFreqDomainData    
Public struct FFTFreqDomainData_DEPRECATED    
Public struct FFTTimeDomainData AudioFFT Deprecation  
Public struct FFTTimeDomainData_DEPRECATED    
Public class FGrain Class representing a grain of audio.  
Public struct FGrainData    
Public class FGrainDelay    
Public class FGrainEnvelope Simple class that generates an envelope and lets you retrieve interpolated values at any given fraction.  
Public class FGranularSynth A stereo granulator.  
Public class FInlineEnvelopeFollower FInlineEnvlepeFollower is useful for low samplerate use cases and where samples are only available one at a time.  
Public struct FInlineEnvelopeFollowerInitParams    
Public class FIntegerDelay An adjustable delay line. Delays values are limited to integer values.  
Public class FInterpolatedHPF    
Public class FInterpolatedLPF    
Public class FLadderFilter    
Public class FLateReflectionsFast FLateReflections generates the long tail reverb of an input audio signal using a relatively fast algorithm using all pass filter delay lines.  
Public struct FLateReflectionsFastSettings Settings for controlling the FLateReflections.  
Public class FLateReflectionsPlate Single plate channel for plate reverberation.  
Public struct FLateReflectionsPlateDelays Delay line settings for reverb plate delay Tap locations are determined by analyzing these delay values.  
Public struct FLateReflectionsPlateOutputs Structure to hold the various delay line tap outputs produced from a plate.  
Public class FLFO Low frequency oscillator.  
Public class FLinearCurve A simple curve class that takes FVector2D points Required to decouple from Engine module  
Public class FLinearEase Simple easing function used to help interpolate params.  
Public class FLinearInterpFractionalDelay Fractional delay using linear interpolation.  
Public class FLinearPitchShifter    
Public struct FLinkwitzRileyBandFilter    
Public class FLinkwitzRileyBandSplitter Helper for Multi-Band processing to generate Linwitz-Riley filtered outputs from input https://en.wikipedia.org/wiki/Linkwitz%E2%80%93Riley_filter  
Public class FLongDelayAPF All Pass Filter with a long delay.  
Public class FMeanSquaredFIR Compute mean squared using FIR method.  
Public class FMeanSquaredIIR Compute mean squared using IIR method.  
Public struct FMelSpectrumKernelSettings Settings for a mel kernel which transforms an linearly space spectrum (e.g. FFT Magnitude) to a mel spectrum  
Public class FMidiNoteQuantizer    
Public class FModulationMatrix    
Public class FMovingAverager This class buffers audio while maintaining a running average of the underlying buffer.  
Public class FMovingVectorAverager Vectorized version of FMovingAverager.  
Public struct FMultibandBuffer    
Public class FMultichannelLinearResampler Linear resampler working on multichannel buffers  
Public class FOnePoleFilter A virtual analog one-pole filter. Defaults to a low-pass mode, but can be switched to high-pass  
Public class FOnePoleLPF Simple 1-pole lowpass filter.  
Public class FOnePoleLPFBank One pole LPF filter for multiple channels  
Public class FOsc Pitched oscillator.  
Public struct FOscFrequencyMod Struct which wraps all factors which contribute to pitch of the oscillator.  
Public class FParam    
Public struct FPassiveFilterParams    
Public struct FPatch    
Public struct FPatchDestination    
Public class FPatchInput Handle to a patch. Should only be used by a single thread.  
Public class FPatchMixer This class is used for retrieving and mixing down audio from multiple threads.  
Public class FPatchMixerSplitter This class is used to mix multiple inputs from disparate threads to a single mixdown and deliver that mixdown to multiple outputs.  
Public struct FPatchOutput This class can be thought of as an output for a single constructed instance of FPatchInput.  
Public struct FPatchSource    
Public class FPatchSplitter This class is used to post audio from one source to multiple threads.  
Public class FPhaser    
Public class FPinkNoise Pink noise generator 1/Frequency noise spectrum  
Public class FPlateReverb    
Public class FPlateReverbFast The Plate Reverb emulates the interactions between a sound, the listener and the space they share.  
Public struct FPlateReverbFastSettings Settings for plate reverb.  
Public struct FPlateReverbSettings    
Public struct FPseudoConstantQ    
Public struct FPseudoConstantQBandSettings Settings for a single constant q band.  
Public struct FPseudoConstantQKernelSettings Settings for Pseudo Constant Q Kernel generation.  
Public struct FrequencyBuffer    
Public class FRingModulation Ring modulation effect https://en.wikipedia.org/wiki/Ring_modulation  
Public class FSampleBufferReader    
Public class FSilenceDetection This object will return buffered audio while the input signal is louder than the specified threshold, and buffer audio when the input signal otherwise.  
Public class FSineOsc FOsc Direct-form sinusoid oscillator.  
Public class FSineWaveTableOsc A sinusoidal wave table oscillator class.  
Public class FSinOsc2DRotation Generates a sine wave in the given buffer with the given frequency.  
Public class FSlowAdaptiveGainControl This object accepts an input buffer and current amplitude estimate of that input buffer, Then applies a computed gain target.  
Public class FSpectrumAnalysisAsyncWorker    
Public class FSpectrumAnalyzer Class built to be a rolling spectrum analyzer for arbitrary, monaural audio data.  
Public class FSpectrumAnalyzerBuffer This class locks an input buffer (for writing) and an output buffer (for reading).  
Public class FSpectrumAnalyzerScopeLock    
Public struct FSpectrumAnalyzerSettings    
Public struct FSpectrumBandExtractorSettings Settings for band extractor.  
Public struct FSpectrumBandExtractorSpectrumSettings Settings describing the spectrum used for in the band extractor.  
Public class FStateVariableFilter    
Public struct FStronglyConnectedComponent A strongly connected component contains a subgraph of strongly connected vertices and their corresponding edges.  
Public class FTapDelayPitchShifter Class which reads doppler-shifted tap from a delay buffer.  
Public class FVariablePoleFilter    
Public struct FVectorLinearResampler FVectorLinearResampler  
Public struct FViterbi    
Public class FVolumeFader Control-rate fader for managing volume fades of various standard shapes.  
Public class FWaveShaper A digital wave shaping effect to cause audio distortion https://en.wikipedia.org/wiki/Waveshaper  
Public class FWaveTableOsc A wave table oscillator class.  
Public struct FWetDry    
Public class FWhiteNoise White noise generator Flat spectrum  
Public class FWindow Class used to generate, contain and apply a DSP window of a given type.  
Public class IChannelFormatConverter Inteface for Channel Format Converters which process deinterleaved audio.  
Public struct IConvertDeinterleave IConvertDeinterleave is an interface for transforming multichannel interleaved audio samples into multichannel deinterleaved samples.  
Public class IConvolutionAlgorithm IConvolutionAlgorithm  
Public class IConvolutionAlgorithmFactory IConvolutionAlgorithmFactory  
Public class IFFTAlgorithm IFFTAlgorithmInterface for FFT algorithm.  
Public class IFFTAlgorithmFactory IFFTAlgorithmFactory  
Public class IFilter Base class for filters usable in synthesis.  
Public class IOscBase Oscillator base class.  
Public class IQuantizedEventListener Event listener interface.  
Public class ISampleRateConverter    
Public class ISpectrumBandExtractor Interface for spectrum band extractors.  
Public class IViterbiInitialProbability Interface class for viterbi initial log probabilities.  
Public class IViterbiObservations Interface class for viterbi observations.  
Public class IViterbiTransitionProbability Interface class for viterbi transition log probabilities.  
Public struct ScaleDegreeSet    
Public class TAutoDeinterleaveView TAutoDeinterleaveView  
Public class TAutoSlidingWindow TAutoSlidingWindow  
Public class TCircularAudioBuffer Basic implementation of a circular buffer built for pushing and popping arbitrary amounts of data at once.  
Public class TDeinterleaveView TDeinterleaveView  
Public struct TGetPower This allows us to write a compile time exponent of a number.  
Public class TParams Simple parameter object which uses critical section to write to and read from data.  
Public class TSample TSample Variant type to simplify converting and performing operations on fixed precision and floating point samples.  
Public class TSampleRef TSampleRef Ref version of TSample.  
Public class TScopedSlidingWindow TScopedSlidingWindow  
Public class TSlidingBuffer TSlidingBuffer  
Public class TSlidingWindow Forward delcaration.  

Constants

Name Description
Audio::ChannelMapMaxNumChannels Maximum number of channels supported by channel maps (Corresponds to 7.1 format)
Audio::ChannelMapVorbisNumChannels Number of channels in a vorbis input (Corresponds to 5.1 with vorbis channel ordering).
Audio::MaxFilterChannels  

Typedefs

Name Description
AlignedByteBuffer Deprecated in favor of versions above.
AlignedFloatBuffer  
AlignedInt32Buffer  
FAlignedByteBuffer  
FAlignedFloatBuffer  
FAlignedInt32Buffer  
FAudioBufferAlignedAllocator Aligned allocator used for fast operations.
FDirectedEdge A pair of int32s represent a directed edge.
FDirectedTree A directed tree graph represenation.
FEnvelope  
FMultichannelBuffer A deinterleaved multichannel buffer
FMultichannelBufferView A deinterleaved multichannel buffer view.
FMultichannelCircularBuffer A deinterleaved multichannel circular buffer
FPatchOutputWeakPtr  
FSpectrumAnalyzerTask  

Enums

  Type Name Description
Public enum Audio::EBiquadFilter::Type Enumeration of filter types.  
Public enum Audio::EChannelMapMonoUpmixMethod Denotes the upmix method for mixing a mono input into the front left and front right speakers.  
Public enum Audio::EChannelMapOrder Denotes the order of gain coefficients for a channel map.  
Public enum Audio::EChorusDelays::Type    
Public enum Audio::EDynamicFilterType NON-UOBJECT LAYER:  
Public enum Audio::EDynamicsProcessingMode::Type What mode the compressor is in.  
Public enum Audio::EDynamicsProcessorChannelLinkMode NON-UOBJECT LAYER:  
Public enum Audio::EEventQuantization NON-UOBJECT LAYER:  
Public enum Audio::EFaderCurve Type of fade to use when adjusting a fader's volume over time.  
Public enum Audio::EFFTScaling EFFTScaling  
Public enum Audio::EFilter::Type    
Public enum Audio::EFilterOrder NON-UOBJECT LAYER:  
Public enum Audio::EGrainEnvelopeType NON-UOBJECT LAYER:  
Public enum Audio::EGranularSynthMode NON-UOBJECT LAYER:  
Public enum Audio::ELFO::Type    
Public enum Audio::ELFOMode::Type    
Public enum Audio::EMelNormalization Normalization methods for a mel transform.  
Public enum Audio::EMusicalScale::Scale Any additions to this Enum should also be added to MetasoundMidiNoteQuantizerNode.cpp in the "#pragma region Metasound Enums" area to show up as options in that Node  
Public enum Audio::EOsc::Type    
Public enum Audio::EPeakMode::Type Different modes for the envelope follower.  
Public enum Audio::EPseudoConstantQNormalization Band normalization schemes  
Public enum Audio::ESeekType::Type    
Public enum Audio::ESpectrumType Types of spectrums which can be directly derived from FFTFreqDomainData.  
Public enum Audio::EStereoDelayMode::Type The different stereo delay modes.  
Public enum Audio::EWaveShaperType NON-UOBJECT LAYER:  
Public enum Audio::EWaveTable::Type Wavetable oscillator types.  
Public enum Audio::EWindowType NON-UOBJECT LAYER:  
Public enum Audio::Grain::EEnvelope Grain envelope types.  

Functions

  Type Name Description
Public function Static void

Audio::CheckSample ( float InSample,
float Threshold
)

 Utility to check for sample clipping.
Public function Static void

Audio::ConvertBipolarBufferToUnipolar ( float* InAlignedBuffer,
int32 NumSamples
)

 Converts in place a buffer into Unipolar (0..1) This is a Vector op version of the GetUnipolar function.
Public function Static float

Audio::ConvertToDecibels ( const float InLinear,
const float InFloor
)

 Function converts linear scale volume to decibels.
Public function Static float

Audio::ConvertToLinear ( const float InDecibels
)

 Function converts decibel to linear scale.
Public function Static void

Audio::DecodeMidSide ( float& MidChannel,
float& SideChannel
)

 Decodes a stereo Mid/Side signal into a stereo Left/Right signal.
Public function Static void

Audio::EncodeMidSide ( float& LeftChannel,
float& RightChannel
)

 Encodes a stereo Left/Right signal into a stereo Mid/Side signal.
Public function Static float

Audio::EvaluateChebyshevPolynomial ( float FrequencyRatio,
int32 Order
)

  
Public function Static float

Audio::FastSin ( const float X
)

 Low precision, high performance approximation of sine using parabolic polynomial approx Valid on interval [-PI, PI]
Public function Static float

Audio::FastSin2 ( const float X
)

 Slightly higher precision, high performance approximation of sine using parabolic polynomial approx.
Public function Static float

Audio::FastSin3 ( const float X
)

 Valid on interval [-PI, PI] Sine approximation using Bhaskara I technique discovered in 7th century.
Public function Static float

Audio::FastTan ( float X
)

 Based on sin parabolic approximation.
Public function Static float

Audio::FastTanh ( float X
)

 Fast tanh based on pade approximation.
Public function Static void

Audio::Filter ( TArrayView< float >& Signal,
const FPassiveFilterParams& InParams
)

 This can be called on any TArrayView whose length is a power of 2.
Public function Static void

Audio::Filter ( TArray< float >& Signal,
const FPassiveFilterParams& InParams
)

 Static function for applying a filter to any time series.
Public function Static float

Audio::GetBandwidthFromQ ( const float InQ
)

 Helper function to get bandwidth from Q.
Public function Static float

Audio::GetBipolar ( const float X
)

 Gets polar value from unipolar.
Public function Static float

Audio::GetFrequencyFromMidi ( const float InMidiNote
)

 Using midi tuning standard, compute frequency in hz from midi value.
Public function Static float

Audio::GetFrequencyMultiplier ( const float InPitchSemitones
)

 Returns the frequency multiplier to scale a base frequency given the input semitones.
Public function Static float

Audio::GetGainForFrequency ( float NormalizedFreq,
const FPassiveFilterParams& InParams
)

  
Public function Static float

Audio::GetGainFromVelocity ( const float InVelocity
)

 Given a velocity value [0,127], return the linear gain.
Public function Static float

Audio::GetLinearFrequencyClamped ( const float InFrequencyValue,
const FVector2D& Domain,
const FVector2D& Range
)

 Returns the linear frequency of the input value. Maps log domain and range values to linear output (good for linear slider representation/visualization of log frequency). Reverse of GetLogFrequencyClamped.
Public function Static float

Audio::GetLogFrequencyClamped ( const float InValue,
const FVector2D& Domain,
const FVector2D& Range
)

 Returns the log frequency of the input value. Maps linear domain and range values to log output (good for linear slider controlling frequency)
Public function Static float

Audio::GetMidiFromFrequency ( const float InFrequency
)

 Using midi tuning standard, compute midi from frequency in hz.
Public function Static float

Audio::GetPitchScaleFromMIDINote ( int32 BaseMidiNote,
int32 TargetMidiNote
)

 Return a pitch scale factor based on the difference between a base midi note and a target midi note. Useful for samplers.
Public function Static float

Audio::GetQFromBandwidth ( const float InBandwidth
)

 Helper function get Q from bandwidth.
Public function Static float

Audio::GetSemitones ( const float InMultiplier
)

 Returns the number of semitones relative to a base frequency given the input frequency multiplier.
Public function Static void

Audio::GetStereoPan ( const float InLinearPan,
float& OutLeft,
float& OutRight
)

 Calculates equal power stereo pan using sinusoidal-panning law and cheap approximation for sin InLinear pan is [-1.0, 1.0] so it can be modulated by a bipolar LFO
Public function Static float

Audio::GetUnipolar ( const float X
)

 Converts bipolar value to unipolar.
Public function Static void

Audio::Grain::GenerateEnvelopeData ( FEnvelope& InData,
const int32 InNumFrames,
const EEnvelope InEnvelopeType
)

 Utility function generates an envelope with the input array for the number of desired frames.
Public function Static float

Audio::Grain::GetValue ( const FEnvelope& InGrainData,
const float InFraction
)

 Returns the interpolated envelope value given the fraction through the grain.
Public function Static float

Audio::LagrangianInterpolation ( const TArray< FVector2D > Points,
const float Alpha
)

 Polynomial interpolation using lagrange polynomials.
Public function Static bool

Audio::QuadraticPeakInterpolation ( const float InValues,
float& OutPeakLoc,
float& OutPeakValue
)

 Given three values, determine peak location and value of quadratic fitted to the data.
Public function void

Audio::SetMultichannelBufferSize ( int32 InNumFrames,
FMultichannelBuffer& OutBuffer
)

 Set the number of frames for a multichannel buffer.
Public function Static float

Audio::UnderflowClamp ( const float InValue
)

 Clamps floats to 0 if they are in sub-normal range.

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