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Biquad.h (4289B)

      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
     62  // conjugate) 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
     66  // conjugate) (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  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, const float* frequency,
     80                            float* magResponse, float* phaseResponse);
     81 
     82 private:
     83  void setNormalizedCoefficients(double b0, double b1, double b2, double a0,
     84                                 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