juce_FilterDesign.h

/*
  ==============================================================================
 
   This file is part of the JUCE library.
   Copyright (c) 2022 - Raw Material Software Limited
 
   JUCE is an open source library subject to commercial or open-source
   licensing.
 
   By using JUCE, you agree to the terms of both the JUCE 7 End-User License
   Agreement and JUCE Privacy Policy.
 
   End User License Agreement: www.juce.com/juce-7-licence
   Privacy Policy: www.juce.com/juce-privacy-policy
 
   Or: You may also use this code under the terms of the GPL v3 (see
   www.gnu.org/licenses).
 
   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.
 
  ==============================================================================
*/
 
namespace juce::dsp
{

template <typename FloatType>
struct FilterDesign
{
    using FIRCoefficientsPtr = typename FIR::Coefficients<FloatType>::Ptr;
    using IIRCoefficients    = typename IIR::Coefficients<FloatType>;
 
    using WindowingMethod    = typename WindowingFunction<FloatType>::WindowingMethod;
 
    //==============================================================================
 
    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);

    struct IIRPolyphaseAllpassStructure
    {
        ReferenceCountedArray<IIRCoefficients> directPath, delayedPath;
        Array<double> alpha;
    };

    static IIRPolyphaseAllpassStructure designIIRLowpassHalfBandPolyphaseAllpassMethod (FloatType normalisedTransitionWidth,
                                                                                        FloatType stopbandAmplitudedB);
 
private:
    //==============================================================================
    static Array<double> getPartialImpulseResponseHn (int n, double kp);
 
    static ReferenceCountedArray<IIRCoefficients> designIIRLowpassHighOrderGeneralMethod (int type, FloatType frequency, double sampleRate,
                                                                                          FloatType normalisedTransitionWidth,
                                                                                          FloatType passbandAmplitudedB,
                                                                                          FloatType stopbandAmplitudedB);
    FilterDesign() = delete;
};
 
} // namespace juce::dsp