Public Types | Public Member Functions | List of all members
dsp::Oversampling< SampleType > Class Template Reference

A processing class performing multi-channel oversampling. More...

Public Types

enum  FilterType { filterHalfBandFIREquiripple = 0, filterHalfBandPolyphaseIIR, numFilterTypes }
 The type of filter that can be used for the oversampling processing. More...
 

Public Member Functions

 Oversampling (size_t numChannels, size_t factor, FilterType type, bool isMaxQuality=true)
 Constructor of the oversampling class. More...
 
 ~Oversampling ()
 Destructor. More...
 
SampleType getLatencyInSamples () noexcept
 Returns the latency in samples of the whole processing. More...
 
size_t getOversamplingFactor () noexcept
 Returns the current oversampling factor. More...
 
void initProcessing (size_t maximumNumberOfSamplesBeforeOversampling)
 Must be called before any processing, to set the buffer sizes of the internal buffers of the oversampling processing. More...
 
void reset () noexcept
 Resets the processing pipeline, ready to oversample a new stream of data. More...
 
dsp::AudioBlock< SampleType > processSamplesUp (const dsp::AudioBlock< SampleType > &inputBlock) noexcept
 Must be called to perform the upsampling, prior to any oversampled processing. More...
 
void processSamplesDown (dsp::AudioBlock< SampleType > &outputBlock) noexcept
 Must be called to perform the downsampling, after the upsampling and the non-linear processing. More...
 

Detailed Description

template<typename SampleType>
class dsp::Oversampling< SampleType >

A processing class performing multi-channel oversampling.

It can be configured to do 2 times, 4 times, 8 times or 16 times oversampling using a multi-stage approach, either polyphase allpass IIR filters or FIR filters for the filtering, and reports successfully the latency added by the filter stages.

The principle of oversampling is to increase the sample rate of a given non-linear process, to prevent it from creating aliasing. Oversampling works by upsampling N times the input signal, processing the upsampling signal with the increased internal sample rate, and downsample the result to get back the original processing sample rate.

Choose between FIR or IIR filtering depending on your needs in term of latency and phase distortion. With FIR filters, the phase is linear but the latency is maximum. With IIR filtering, the phase is compromised around the Nyquist frequency but the latency is minimum.

See also
FilterDesign.

Member Enumeration Documentation

◆ FilterType

template<typename SampleType >
enum dsp::Oversampling::FilterType

The type of filter that can be used for the oversampling processing.

Enumerator
filterHalfBandFIREquiripple 
filterHalfBandPolyphaseIIR 
numFilterTypes 

Constructor & Destructor Documentation

◆ Oversampling()

template<typename SampleType >
dsp::Oversampling< SampleType >::Oversampling ( size_t  numChannels,
size_t  factor,
FilterType  type,
bool  isMaxQuality = true 
)

Constructor of the oversampling class.

All the processing parameters must be provided at the creation of the oversampling object.

Note : you might want to create a class heriting from Oversampling with a different constructor if you need more control on what happens in the process.

Parameters
numChannelsthe number of channels to process with this object
factorthe processing will perform 2 ^ factor times oversampling
typethe type of filter design employed for filtering during oversampling
isMaxQualityif the oversampling is done using the maximum quality, the filters will be more efficient, but the CPU load will increase as well

◆ ~Oversampling()

template<typename SampleType >
dsp::Oversampling< SampleType >::~Oversampling ( )

Destructor.

Member Function Documentation

◆ getLatencyInSamples()

template<typename SampleType >
SampleType dsp::Oversampling< SampleType >::getLatencyInSamples ( )
noexcept

Returns the latency in samples of the whole processing.

Use this information in your main processor to compensate the additional latency involved with the oversampling, for example with a dry / wet functionality, and to report the latency to the DAW.

Note : the latency might not be integer, so you might need to round its value or to compensate it properly in your processing code.

◆ getOversamplingFactor()

template<typename SampleType >
size_t dsp::Oversampling< SampleType >::getOversamplingFactor ( )
noexcept

Returns the current oversampling factor.

◆ initProcessing()

template<typename SampleType >
void dsp::Oversampling< SampleType >::initProcessing ( size_t  maximumNumberOfSamplesBeforeOversampling)

Must be called before any processing, to set the buffer sizes of the internal buffers of the oversampling processing.

◆ reset()

template<typename SampleType >
void dsp::Oversampling< SampleType >::reset ( )
noexcept

Resets the processing pipeline, ready to oversample a new stream of data.

◆ processSamplesUp()

template<typename SampleType >
dsp::AudioBlock<SampleType> dsp::Oversampling< SampleType >::processSamplesUp ( const dsp::AudioBlock< SampleType > &  inputBlock)
noexcept

Must be called to perform the upsampling, prior to any oversampled processing.

Returns an AudioBlock referencing the oversampled input signal, which must be used to perform the non-linear processing which needs the higher sample rate. Don't forget to set the sample rate of that processing to N times the original sample rate.

◆ processSamplesDown()

template<typename SampleType >
void dsp::Oversampling< SampleType >::processSamplesDown ( dsp::AudioBlock< SampleType > &  outputBlock)
noexcept

Must be called to perform the downsampling, after the upsampling and the non-linear processing.

The output signal is probably delayed by the internal latency of the whole oversampling behaviour, so don't forget to take this into account.


The documentation for this class was generated from the following file: