/*

 * 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

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 */

#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