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dsp::Convolution Class Reference

Performs stereo partitioned convolution of an input signal with an impulse response in the frequency domain, using the JUCE FFT class. More...

Classes

struct  Latency
 Contains configuration information for a convolution with a fixed latency. More...
 
struct  NonUniform
 Contains configuration information for a non-uniform convolution. More...
 

Public Types

enum  Stereo { Stereo::no, Stereo::yes }
 
enum  Trim { Trim::no, Trim::yes }
 
enum  Normalise { Normalise::no, Normalise::yes }
 

Public Member Functions

 Convolution ()
 Initialises an object for performing convolution in the frequency domain. More...
 
 Convolution (ConvolutionMessageQueue &queue)
 Initialises a convolution engine using a shared background message queue. More...
 
 Convolution (const Latency &requiredLatency)
 Initialises an object for performing convolution with a fixed latency. More...
 
 Convolution (const NonUniform &requiredHeadSize)
 Initialises an object for performing convolution in the frequency domain using a non-uniform partitioned algorithm. More...
 
 Convolution (const Latency &, ConvolutionMessageQueue &)
 Behaves the same as the constructor taking a single Latency argument, but with a shared background message queue. More...
 
 Convolution (const NonUniform &, ConvolutionMessageQueue &)
 Behaves the same as the constructor taking a single NonUniform argument, but with a shared background message queue. More...
 
 ~Convolution () noexcept
 
void prepare (const ProcessSpec &)
 Must be called before loading any impulse response. More...
 
void reset () noexcept
 Resets the processing pipeline ready to start a new stream of data. More...
 
template<typename ProcessContext , std::enable_if_t< std::is_same< typename ProcessContext::SampleType, float >::value, int > = 0>
void process (const ProcessContext &context) noexcept
 Performs the filter operation on the given set of samples with optional stereo processing. More...
 
void loadImpulseResponse (const void *sourceData, size_t sourceDataSize, Stereo isStereo, Trim requiresTrimming, size_t size, Normalise requiresNormalisation=Normalise::yes)
 This function loads an impulse response audio file from memory, added in a JUCE project with the Projucer as binary data. More...
 
void loadImpulseResponse (const File &fileImpulseResponse, Stereo isStereo, Trim requiresTrimming, size_t size, Normalise requiresNormalisation=Normalise::yes)
 This function loads an impulse response from an audio file. More...
 
void loadImpulseResponse (AudioBuffer< float > &&buffer, double bufferSampleRate, Stereo isStereo, Trim requiresTrimming, Normalise requiresNormalisation)
 This function loads an impulse response from an audio buffer. More...
 
int getCurrentIRSize () const
 This function returns the size of the current IR in samples. More...
 
int getLatency () const
 This function returns the current latency of the process in samples. More...
 

Detailed Description

Performs stereo partitioned convolution of an input signal with an impulse response in the frequency domain, using the JUCE FFT class.

This class provides some thread-safe functions to load impulse responses from audio files or memory on-the-fly without noticeable artefacts, performing resampling and trimming if necessary.

The processing performed by this class is equivalent to the time domain convolution done in the FIRFilter class, with a FIRFilter::Coefficients object having the samples of the impulse response as its coefficients. However, in general it is more efficient to do frequency domain convolution when the size of the impulse response is 64 samples or greater.

Note: The default operation of this class uses zero latency and a uniform partitioned algorithm. If the impulse response size is large, or if the algorithm is too CPU intensive, it is possible to use either a fixed latency version of the algorithm, or a simple non-uniform partitioned convolution algorithm.

Threading: It is not safe to interleave calls to the methods of this class. If you need to load new impulse responses during processing the load calls must be synchronised with process calls, which in practice means making the load call from the audio thread. The loadImpulseResponse functions are wait-free and are therefore suitable for use in a realtime context.

See also
FIRFilter, FIRFilter::Coefficients, FFT

Member Enumeration Documentation

◆ Stereo

Enumerator
no 
yes 

◆ Trim

Enumerator
no 
yes 

◆ Normalise

Enumerator
no 
yes 

Constructor & Destructor Documentation

◆ Convolution() [1/6]

dsp::Convolution::Convolution ( )

Initialises an object for performing convolution in the frequency domain.

◆ Convolution() [2/6]

dsp::Convolution::Convolution ( ConvolutionMessageQueue queue)
explicit

Initialises a convolution engine using a shared background message queue.

IMPORTANT: the queue must remain alive throughout the lifetime of the Convolution.

◆ Convolution() [3/6]

dsp::Convolution::Convolution ( const Latency requiredLatency)
explicit

Initialises an object for performing convolution with a fixed latency.

If the requested latency is zero, the actual latency will also be zero. For requested latencies greater than zero, the actual latency will always at least as large as the requested latency. Using a fixed non-zero latency can reduce the CPU consumption of the convolution algorithm.

Parameters
requiredLatencythe minimum latency

◆ Convolution() [4/6]

dsp::Convolution::Convolution ( const NonUniform requiredHeadSize)
explicit

Initialises an object for performing convolution in the frequency domain using a non-uniform partitioned algorithm.

A requiredHeadSize of 256 samples or greater will improve the efficiency of the processing for IR sizes of 4096 samples or greater (recommended for reverberation IRs).

Parameters
requiredHeadSizethe head IR size for two stage non-uniform partitioned convolution

◆ Convolution() [5/6]

dsp::Convolution::Convolution ( const Latency ,
ConvolutionMessageQueue  
)

Behaves the same as the constructor taking a single Latency argument, but with a shared background message queue.

IMPORTANT: the queue must remain alive throughout the lifetime of the Convolution.

◆ Convolution() [6/6]

dsp::Convolution::Convolution ( const NonUniform ,
ConvolutionMessageQueue  
)

Behaves the same as the constructor taking a single NonUniform argument, but with a shared background message queue.

IMPORTANT: the queue must remain alive throughout the lifetime of the Convolution.

◆ ~Convolution()

dsp::Convolution::~Convolution ( )
noexcept

Member Function Documentation

◆ prepare()

void dsp::Convolution::prepare ( const ProcessSpec )

Must be called before loading any impulse response.

This provides the maximumBufferSize and the sample rate required for any resampling.

◆ reset()

void dsp::Convolution::reset ( )
noexcept

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

◆ process()

template<typename ProcessContext , std::enable_if_t< std::is_same< typename ProcessContext::SampleType, float >::value, int > = 0>
void dsp::Convolution::process ( const ProcessContext &  context)
noexcept

Performs the filter operation on the given set of samples with optional stereo processing.

◆ loadImpulseResponse() [1/3]

void dsp::Convolution::loadImpulseResponse ( const void *  sourceData,
size_t  sourceDataSize,
Stereo  isStereo,
Trim  requiresTrimming,
size_t  size,
Normalise  requiresNormalisation = Normalise::yes 
)

This function loads an impulse response audio file from memory, added in a JUCE project with the Projucer as binary data.

It can load any of the audio formats registered in JUCE, and performs some resampling and pre-processing as well if needed.

Note: Don't try to use this function on float samples, since the data is expected to be an audio file in its binary format. Be sure that the original data remains constant throughout the lifetime of the Convolution object, as the loading process will happen on a background thread once this function has returned.

Parameters
sourceDatathe block of data to use as the stream's source
sourceDataSizethe number of bytes in the source data block
isStereoselects either stereo or mono
requiresTrimmingoptionally trim the start and the end of the impulse response
sizethe expected size for the impulse response after loading, can be set to 0 to requesting the original impulse response size
requiresNormalisationoptionally normalise the impulse response amplitude

◆ loadImpulseResponse() [2/3]

void dsp::Convolution::loadImpulseResponse ( const File fileImpulseResponse,
Stereo  isStereo,
Trim  requiresTrimming,
size_t  size,
Normalise  requiresNormalisation = Normalise::yes 
)

This function loads an impulse response from an audio file.

It can load any of the audio formats registered in JUCE, and performs some resampling and pre-processing as well if needed.

Parameters
fileImpulseResponsethe location of the audio file
isStereoselects either stereo or mono
requiresTrimmingoptionally trim the start and the end of the impulse response
sizethe expected size for the impulse response after loading, can be set to 0 to requesting the original impulse response size
requiresNormalisationoptionally normalise the impulse response amplitude

◆ loadImpulseResponse() [3/3]

void dsp::Convolution::loadImpulseResponse ( AudioBuffer< float > &&  buffer,
double  bufferSampleRate,
Stereo  isStereo,
Trim  requiresTrimming,
Normalise  requiresNormalisation 
)

This function loads an impulse response from an audio buffer.

To avoid memory allocation on the audio thread, this function takes ownership of the buffer passed in.

If calling this function during processing, make sure that the buffer is not allocated on the audio thread (be careful of accidental copies!). If you need to pass arbitrary/generated buffers it's recommended to create these buffers on a separate thread and to use some wait-free construct (a lock-free queue or a SpinLock/GenericScopedTryLock combination) to transfer ownership to the audio thread without allocating.

Parameters
bufferthe AudioBuffer to use
bufferSampleRatethe sampleRate of the data in the AudioBuffer
isStereoselects either stereo or mono
requiresTrimmingoptionally trim the start and the end of the impulse response
requiresNormalisationoptionally normalise the impulse response amplitude

◆ getCurrentIRSize()

int dsp::Convolution::getCurrentIRSize ( ) const

This function returns the size of the current IR in samples.

◆ getLatency()

int dsp::Convolution::getLatency ( ) const

This function returns the current latency of the process in samples.

Note: This is the latency of the convolution engine, not the latency associated with the current impulse response choice that has to be considered separately (linear phase filters, for eaxmple).


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