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