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JUCE
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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 (size_t numChannels=1) | |
| The default constructor of the oversampling class, which can be used to create an empty object and then add the appropriate stages. More... | |
| ~Oversampling () | |
| Destructor. More... | |
| SampleType | getLatencyInSamples () const noexcept |
| Returns the latency in samples of the whole processing. More... | |
| size_t | getOversamplingFactor () const 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... | |
| AudioBlock< SampleType > | processSamplesUp (const AudioBlock< const SampleType > &inputBlock) noexcept |
| Must be called to perform the upsampling, prior to any oversampled processing. More... | |
| void | processSamplesDown (AudioBlock< SampleType > &outputBlock) noexcept |
| Must be called to perform the downsampling, after the upsampling and the non-linear processing. More... | |
| void | addOversamplingStage (FilterType, float normalisedTransitionWidthUp, float stopbandAmplitudedBUp, float normalisedTransitionWidthDown, float stopbandAmplitudedBDown) |
| Adds a new oversampling stage to the Oversampling class, multiplying the current oversampling factor by two. More... | |
| void | addDummyOversamplingStage () |
| Adds a new "dummy" oversampling stage, which does nothing to the signal. More... | |
| void | clearOversamplingStages () |
| Removes all the previously registered oversampling stages, so you can add your own from scratch. More... | |
Public Attributes | |
| size_t | factorOversampling = 1 |
| size_t | numChannels = 1 |
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 upsampled signal with the increased internal sample rate, and downsampling 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 maximised. With IIR filtering, the phase is compromised around the Nyquist frequency but the latency is minimised.
| enum dsp::Oversampling::FilterType |
| dsp::Oversampling< SampleType >::Oversampling | ( | size_t | numChannels, |
| size_t | factor, | ||
| FilterType | type, | ||
| bool | isMaxQuality = true |
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| ) |
Constructor of the oversampling class.
All the processing parameters must be provided at the creation of the oversampling object.
| numChannels | the number of channels to process with this object |
| factor | the processing will perform 2 ^ factor times oversampling |
| type | the type of filter design employed for filtering during oversampling |
| isMaxQuality | if the oversampling is done using the maximum quality, the filters will be more efficient, but the CPU load will increase as well |
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explicit |
The default constructor of the oversampling class, which can be used to create an empty object and then add the appropriate stages.
Note: This creates a "dummy" oversampling stage, which needs to be removed first before adding proper oversampling stages.
| dsp::Oversampling< SampleType >::~Oversampling | ( | ) |
Destructor.
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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.
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noexcept |
Returns the current oversampling factor.
| 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.
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noexcept |
Resets the processing pipeline, ready to oversample a new stream of data.
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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.
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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.
| void dsp::Oversampling< SampleType >::addOversamplingStage | ( | FilterType | , |
| float | normalisedTransitionWidthUp, | ||
| float | stopbandAmplitudedBUp, | ||
| float | normalisedTransitionWidthDown, | ||
| float | stopbandAmplitudedBDown | ||
| ) |
Adds a new oversampling stage to the Oversampling class, multiplying the current oversampling factor by two.
This is used with the default constructor to create custom oversampling chains, requiring a call to the clearOversamplingStages before any addition.
Note: Upsampling and downsampling filtering have different purposes, the former removes upsampling artefacts while the latter removes useless frequency content created by the oversampled process, so usually the attenuation is increased when upsampling compared to downsampling.
| normalisedTransitionWidthUp | a value between 0 and 0.5 which specifies how much the transition between passband and stopband is steep, for upsampling filtering (the lower the better) |
| stopbandAmplitudedBUp | the amplitude in dB in the stopband for upsampling filtering, must be negative |
| normalisedTransitionWidthDown | a value between 0 and 0.5 which specifies how much the transition between passband and stopband is steep, for downsampling filtering (the lower the better) |
| stopbandAmplitudedBDown | the amplitude in dB in the stopband for downsampling filtering, must be negative |
| void dsp::Oversampling< SampleType >::addDummyOversamplingStage | ( | ) |
Adds a new "dummy" oversampling stage, which does nothing to the signal.
Using one can be useful if your application features a customisable oversampling factor and if you want to select the current one from an OwnedArray without changing anything in the processing code.
| void dsp::Oversampling< SampleType >::clearOversamplingStages | ( | ) |
Removes all the previously registered oversampling stages, so you can add your own from scratch.
| size_t dsp::Oversampling< SampleType >::factorOversampling = 1 |
| size_t dsp::Oversampling< SampleType >::numChannels = 1 |
1.8.13