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101 lines
3.9 KiB
C++
101 lines
3.9 KiB
C++
/*
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* Copyright (C) 2010 Google Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
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* its contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef Biquad_h
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#define Biquad_h
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#include <complex>
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namespace WebCore {
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typedef std::complex<double> Complex;
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// A basic biquad (two-zero / two-pole digital filter)
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//
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// It can be configured to a number of common and very useful filters:
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// lowpass, highpass, shelving, parameteric, notch, allpass, ...
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class Biquad {
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public:
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Biquad();
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~Biquad();
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void process(const float* sourceP, float* destP, size_t framesToProcess);
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// frequency is 0 - 1 normalized, resonance and dbGain are in decibels.
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// Q is a unitless quality factor.
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void setLowpassParams(double frequency, double resonance);
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void setHighpassParams(double frequency, double resonance);
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void setBandpassParams(double frequency, double Q);
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void setLowShelfParams(double frequency, double dbGain);
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void setHighShelfParams(double frequency, double dbGain);
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void setPeakingParams(double frequency, double Q, double dbGain);
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void setAllpassParams(double frequency, double Q);
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void setNotchParams(double frequency, double Q);
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// Set the biquad coefficients given a single zero (other zero will be conjugate)
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// and a single pole (other pole will be conjugate)
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void setZeroPolePairs(const Complex& zero, const Complex& pole);
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// Set the biquad coefficients given a single pole (other pole will be conjugate)
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// (The zeroes will be the inverse of the poles)
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void setAllpassPole(const Complex& pole);
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// Resets filter state
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void reset();
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// Filter response at a set of n frequencies. The magnitude and
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// phase response are returned in magResponse and phaseResponse.
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// The phase response is in radians.
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void getFrequencyResponse(int nFrequencies,
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const float* frequency,
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float* magResponse,
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float* phaseResponse);
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private:
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void setNormalizedCoefficients(double b0, double b1, double b2, double a0, double a1, double a2);
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// Filter coefficients. The filter is defined as
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//
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// y[n] + m_a1*y[n-1] + m_a2*y[n-2] = m_b0*x[n] + m_b1*x[n-1] + m_b2*x[n-2].
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double m_b0;
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double m_b1;
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double m_b2;
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double m_a1;
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double m_a2;
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// Filter memory
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double m_x1; // input delayed by 1 sample
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double m_x2; // input delayed by 2 samples
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double m_y1; // output delayed by 1 sample
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double m_y2; // output delayed by 2 samples
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};
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} // namespace WebCore
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#endif // Biquad_h
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