Line data    Source code

       1             : /*
       2             :  * Copyright (C) 2010 Google Inc. All rights reserved.
       3             :  *
       4             :  * Redistribution and use in source and binary forms, with or without
       5             :  * modification, are permitted provided that the following conditions
       6             :  * are met:
       7             :  *
       8             :  * 1.  Redistributions of source code must retain the above copyright
       9             :  *     notice, this list of conditions and the following disclaimer.
      10             :  * 2.  Redistributions in binary form must reproduce the above copyright
      11             :  *     notice, this list of conditions and the following disclaimer in the
      12             :  *     documentation and/or other materials provided with the distribution.
      13             :  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
      14             :  *     its contributors may be used to endorse or promote products derived
      15             :  *     from this software without specific prior written permission.
      16             :  *
      17             :  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
      18             :  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
      19             :  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
      20             :  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
      21             :  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
      22             :  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
      23             :  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
      24             :  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
      25             :  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
      26             :  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
      27             :  */
      28             : 
      29             : #ifndef Biquad_h
      30             : #define Biquad_h
      31             : 
      32             : #include <complex>
      33             : 
      34             : namespace WebCore {
      35             : 
      36             : typedef std::complex<double> Complex;
      37             : 
      38             : // A basic biquad (two-zero / two-pole digital filter)
      39             : //
      40             : // It can be configured to a number of common and very useful filters:
      41             : //    lowpass, highpass, shelving, parameteric, notch, allpass, ...
      42             : 
      43             : class Biquad {
      44             : public:
      45             :     Biquad();
      46             :     ~Biquad();
      47             : 
      48             :     void process(const float* sourceP, float* destP, size_t framesToProcess);
      49             : 
      50             :     // frequency is 0 - 1 normalized, resonance and dbGain are in decibels.
      51             :     // Q is a unitless quality factor.
      52             :     void setLowpassParams(double frequency, double resonance);
      53             :     void setHighpassParams(double frequency, double resonance);
      54             :     void setBandpassParams(double frequency, double Q);
      55             :     void setLowShelfParams(double frequency, double dbGain);
      56             :     void setHighShelfParams(double frequency, double dbGain);
      57             :     void setPeakingParams(double frequency, double Q, double dbGain);
      58             :     void setAllpassParams(double frequency, double Q);
      59             :     void setNotchParams(double frequency, double Q);
      60             : 
      61             :     // Set the biquad coefficients given a single zero (other zero will be conjugate)
      62             :     // and a single pole (other pole will be conjugate)
      63             :     void setZeroPolePairs(const Complex& zero, const Complex& pole);
      64             : 
      65             :     // Set the biquad coefficients given a single pole (other pole will be conjugate)
      66             :     // (The zeroes will be the inverse of the poles)
      67             :     void setAllpassPole(const Complex& pole);
      68             : 
      69             :     // Return true iff the next output block will contain sound even with
      70             :     // silent input.
      71           0 :     bool hasTail() const { return m_y1 || m_y2 || m_x1 || m_x2; }
      72             : 
      73             :     // Resets filter state
      74             :     void reset();
      75             : 
      76             :     // Filter response at a set of n frequencies. The magnitude and
      77             :     // phase response are returned in magResponse and phaseResponse.
      78             :     // The phase response is in radians.
      79             :     void getFrequencyResponse(int nFrequencies,
      80             :                               const float* frequency,
      81             :                               float* magResponse,
      82             :                               float* phaseResponse);
      83             : private:
      84             :     void setNormalizedCoefficients(double b0, double b1, double b2, double a0, double a1, double a2);
      85             : 
      86             :     // Filter coefficients. The filter is defined as
      87             :     //
      88             :     // 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].
      89             :     double m_b0;
      90             :     double m_b1;
      91             :     double m_b2;
      92             :     double m_a1;
      93             :     double m_a2;
      94             : 
      95             :     // Filter memory
      96             :     //
      97             :     // Double precision for the output values is valuable because errors can
      98             :     // accumulate.  Input values are also stored as double so they need not be
      99             :     // converted again for computation.
     100             :     double m_x1; // input delayed by 1 sample
     101             :     double m_x2; // input delayed by 2 samples
     102             :     double m_y1; // output delayed by 1 sample
     103             :     double m_y2; // output delayed by 2 samples
     104             : };
     105             : 
     106             : } // namespace WebCore
     107             : 
     108             : #endif // Biquad_h