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- /*******************************************************************************
-
- "A Collection of Useful C++ Classes for Digital Signal Processing"
- By Vinnie Falco
-
- Official project location:
- https://github.com/vinniefalco/DSPFilters
-
- See Documentation.cpp for contact information, notes, and bibliography.
-
- --------------------------------------------------------------------------------
-
- License: MIT License (http://www.opensource.org/licenses/mit-license.php)
- Copyright (c) 2009 by Vinnie Falco
-
- Permission is hereby granted, free of charge, to any person obtaining a copy
- of this software and associated documentation files (the "Software"), to deal
- in the Software without restriction, including without limitation the rights
- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- copies of the Software, and to permit persons to whom the Software is
- furnished to do so, subject to the following conditions:
-
- The above copyright notice and this permission notice shall be included in
- all copies or substantial portions of the Software.
-
- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- THE SOFTWARE.
-
- *******************************************************************************/
-
- #pragma once
-
- #include "Common.h"
- #include "MathSupplement.h"
- #include "Cascade.h"
-
- namespace Dsp
- {
-
- /*
- * Base for filters designed via algorithmic placement of poles and zeros.
- *
- * Typically, the filter is first designed as a half-band low pass or
- * low shelf analog filter (s-plane). Then, using a transformation such
- * as the ones from Constantinides, the poles and zeros of the analog filter
- * are calculated in the z-plane.
- *
- */
-
- // Factored implementations to reduce template instantiations
-
- class PoleFilterBase2 : public Cascade
- {
- public:
- // This gets the poles/zeros directly from the digital
- // prototype. It is used to double check the correctness
- // of the recovery of pole/zeros from biquad coefficients.
- //
- // It can also be used to accelerate the interpolation
- // of pole/zeros for parameter modulation, since a pole
- // filter already has them calculated
-
- #if 1
- // Commenting this out will pass the call to the Cascade,
- // which tries to compute the poles and zeros from the biquad
- // coefficients.
- std::vector<PoleZeroPair> getPoleZeros() const
- {
- std::vector<PoleZeroPair> vpz;
- const int pairs = (m_digitalProto.getNumPoles() + 1) / 2;
- for (int i = 0; i < pairs; ++i) { vpz.push_back(m_digitalProto[i]); }
- return vpz;
- }
- #endif
-
- protected:
- LayoutBase m_digitalProto;
- };
-
- // Serves a container to hold the analog prototype
- // and the digital pole/zero layout.
- template <class AnalogPrototype>
- class PoleFilterBase : public PoleFilterBase2
- {
- protected:
- void setPrototypeStorage(const LayoutBase& analogStorage, const LayoutBase& digitalStorage)
- {
- m_analogProto.setStorage(analogStorage);
- m_digitalProto = digitalStorage;
- }
-
- AnalogPrototype m_analogProto;
- };
-
- //------------------------------------------------------------------------------
-
- // Storage for pole filters
- template <class BaseClass,
- int MaxAnalogPoles,
- int MaxDigitalPoles = MaxAnalogPoles>
- struct PoleFilter : BaseClass
- , CascadeStages<(MaxDigitalPoles + 1) / 2>
- {
- PoleFilter()
- {
- // This glues together the factored base classes
- // with the templatized storage classes.
- BaseClass::setCascadeStorage(this->getCascadeStorage());
- BaseClass::setPrototypeStorage(m_analogStorage, m_digitalStorage);
- }
-
- private:
- Layout<MaxAnalogPoles> m_analogStorage;
- Layout<MaxDigitalPoles> m_digitalStorage;
- };
-
- //------------------------------------------------------------------------------
-
- /*
- * s-plane to z-plane transforms
- *
- * For pole filters, an analog prototype is created via placement of
- * poles and zeros in the s-plane. The analog prototype is either
- * a halfband low pass or a halfband low shelf. The poles, zeros,
- * and normalization parameters are transformed into the z-plane
- * using variants of the bilinear transformation.
- *
- */
-
- // low pass to low pass
- class LowPassTransform
- {
- public:
- LowPassTransform(double fc, LayoutBase& digital, LayoutBase const& analog);
-
- private:
- complex_t transform(complex_t c) const;
-
- double f = 0;
- };
-
- //------------------------------------------------------------------------------
-
- // low pass to high pass
- class HighPassTransform
- {
- public:
- HighPassTransform(double fc, LayoutBase& digital, LayoutBase const& analog);
-
- private:
- complex_t transform(complex_t c) const;
-
- double f = 0;
- };
-
- //------------------------------------------------------------------------------
-
- // low pass to band pass transform
- class BandPassTransform
- {
- public:
- BandPassTransform(double fc, double fw, LayoutBase& digital, LayoutBase const& analog);
-
- private:
- ComplexPair transform(complex_t c) const;
-
- double wc = 0;
- double wc2 = 0;
- double a = 0;
- double b = 0;
- double a2 = 0;
- double b2 = 0;
- double ab = 0;
- double ab_2 = 0;
- };
-
- //------------------------------------------------------------------------------
-
- // low pass to band stop transform
- class BandStopTransform
- {
- public:
- BandStopTransform(double fc, double fw, LayoutBase& digital, LayoutBase const& analog);
-
- private:
- ComplexPair transform(complex_t c) const;
-
- double wc = 0;
- double wc2 = 0;
- double a = 0;
- double b = 0;
- double a2 = 0;
- double b2 = 0;
- };
- } // namespace Dsp
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