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| static FIRCoefficientsPtr | designFIRLowpassWindowMethod (FloatType frequency, double sampleRate, size_t order, WindowingMethod type, FloatType beta=static_cast< FloatType >(2)) |
| static FIRCoefficientsPtr | designFIRLowpassKaiserMethod (FloatType frequency, double sampleRate, FloatType normalisedTransitionWidth, FloatType amplitudedB) |
| static FIRCoefficientsPtr | designFIRLowpassTransitionMethod (FloatType frequency, double sampleRate, size_t order, FloatType normalisedTransitionWidth, FloatType spline) |
| static FIRCoefficientsPtr | designFIRLowpassLeastSquaresMethod (FloatType frequency, double sampleRate, size_t order, FloatType normalisedTransitionWidth, FloatType stopBandWeight) |
| static FIRCoefficientsPtr | designFIRLowpassHalfBandEquirippleMethod (FloatType normalisedTransitionWidth, FloatType amplitudedB) |
| static ReferenceCountedArray< IIRCoefficients > | designIIRLowpassHighOrderButterworthMethod (FloatType frequency, double sampleRate, FloatType normalisedTransitionWidth, FloatType passbandAmplitudedB, FloatType stopbandAmplitudedB) |
| static ReferenceCountedArray< IIRCoefficients > | designIIRLowpassHighOrderButterworthMethod (FloatType frequency, double sampleRate, int order) |
| static ReferenceCountedArray< IIRCoefficients > | designIIRHighpassHighOrderButterworthMethod (FloatType frequency, double sampleRate, int order) |
| static ReferenceCountedArray< IIRCoefficients > | designIIRLowpassHighOrderChebyshev1Method (FloatType frequency, double sampleRate, FloatType normalisedTransitionWidth, FloatType passbandAmplitudedB, FloatType stopbandAmplitudedB) |
| static ReferenceCountedArray< IIRCoefficients > | designIIRLowpassHighOrderChebyshev2Method (FloatType frequency, double sampleRate, FloatType normalisedTransitionWidth, FloatType passbandAmplitudedB, FloatType stopbandAmplitudedB) |
| static ReferenceCountedArray< IIRCoefficients > | designIIRLowpassHighOrderEllipticMethod (FloatType frequency, double sampleRate, FloatType normalisedTransitionWidth, FloatType passbandAmplitudedB, FloatType stopbandAmplitudedB) |
| static IIRPolyphaseAllpassStructure | designIIRLowpassHalfBandPolyphaseAllpassMethod (FloatType normalisedTransitionWidth, FloatType stopbandAmplitudedB) |
template<typename FloatType>
struct juce::dsp::FilterDesign< FloatType >
This class provides a set of functions which generates FIR::Coefficients and IIR::Coefficients, of high-order low-pass filters. They can be used for processing directly audio as an equalizer, in resampling algorithms etc.
see FIRFilter::Coefficients, FIRFilter, WindowingFunction, IIRFilter::Coefficients, IIRFilter
@tags{DSP}
template<typename FloatType>
This method generates a FIR::Coefficients for a low-pass filter, with a cutoff frequency at half band, using an algorithm described in the article "Design of Half-Band FIR Filters for Signal Compression" from Pavel Zahradnik, to get an equiripple like high order FIR filter, without the need of an iterative method and convergence failure risks.
It generates linear phase filters coefficients.
- Parameters
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| normalisedTransitionWidth | the normalised size between 0 and 0.5 of the transition between the pass band and the stop band |
| amplitudedB | the maximum amplitude in dB expected in the stop band (must be negative) |
template<typename FloatType>
| FIR::Coefficients< FloatType >::Ptr juce::dsp::FilterDesign< FloatType >::designFIRLowpassKaiserMethod |
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FloatType | frequency, |
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double | sampleRate, |
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FloatType | normalisedTransitionWidth, |
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FloatType | amplitudedB ) |
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This a variant of the function designFIRLowpassWindowMethod, which allows the user to specify a transition width and a negative gain in dB, to get a low-pass filter using the Kaiser windowing function, with calculated values of the filter order and of the beta parameter, to satisfy the constraints.
It generates linear phase filters coefficients.
- Parameters
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| frequency | the cutoff frequency of the low-pass filter |
| sampleRate | the sample rate being used in the filter design |
| normalisedTransitionWidth | the normalised size between 0 and 0.5 of the transition between the pass band and the stop band |
| amplitudedB | the maximum amplitude in dB expected in the stop band (must be negative) |
template<typename FloatType>
| FIR::Coefficients< FloatType >::Ptr juce::dsp::FilterDesign< FloatType >::designFIRLowpassTransitionMethod |
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FloatType | frequency, |
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double | sampleRate, |
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size_t | order, |
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FloatType | normalisedTransitionWidth, |
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FloatType | spline ) |
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static |
This method is also a variant of the function designFIRLowpassWindowMethod, using a rectangular window as a basis, and a spline transition between the pass band and the stop band, to reduce the Gibbs phenomenon.
It generates linear phase filters coefficients.
- Parameters
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| frequency | the cutoff frequency of the low-pass filter |
| sampleRate | the sample rate being used in the filter design |
| order | the order of the filter |
| normalisedTransitionWidth | the normalised size between 0 and 0.5 of the transition between the pass band and the stop band |
| spline | between 1.0 and 4.0, indicates how much the transition is curved, with 1.0 meaning a straight line |
template<typename FloatType>
This method generates a FIR::Coefficients for a low-pass filter, using the windowing design method, applied to a sinc impulse response. It is one of the simplest method used to generate a high order low-pass filter, which has the downside of needing more coefficients than more complex method to perform a given attenuation in the stop band.
It generates linear phase filters coefficients.
Note: The flatTop WindowingMethod generates an impulse response with a maximum amplitude higher than one, and might be normalised if necessary depending on the applications.
- Parameters
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| frequency | the cutoff frequency of the low-pass filter |
| sampleRate | the sample rate being used in the filter design |
| order | the order of the filter |
| type | the type, must be a WindowingFunction::WindowingType |
| beta | an optional additional parameter useful for the Kaiser windowing function |
template<typename FloatType>
This method generates arrays of IIR::Coefficients for a low-pass filter, with a cutoff frequency at half band, using an algorithm described in the article "Digital Signal Processing Schemes for efficient interpolation and decimation" from Pavel Valenzuela and Constantinides.
The result is a IIRPolyphaseAllpassStructure object.
The two members of this structure directPath and delayedPath are arrays of IIR::Coefficients, made of polyphase second order allpass filters and an additional delay in the second array, that can be used in cascaded filters processed in two parallel paths, which must be summed at the end to get the high order efficient low-pass filtering.
The gain of the resulting pass-band is 6 dB, so don't forget to compensate it if you want to use that method for something else than two times oversampling.
- Parameters
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| normalisedTransitionWidth | the normalised size between 0 and 0.5 of the transition between the pass band and the stop band |
| stopbandAmplitudedB | the maximum amplitude in dB expected in the stop band (must be negative) |
1.16.1