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