1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/content/media/webaudio/blink/Biquad.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,108 @@
1.4 +/*
1.5 + * Copyright (C) 2010 Google Inc. All rights reserved.
1.6 + *
1.7 + * Redistribution and use in source and binary forms, with or without
1.8 + * modification, are permitted provided that the following conditions
1.9 + * are met:
1.10 + *
1.11 + * 1. Redistributions of source code must retain the above copyright
1.12 + * notice, this list of conditions and the following disclaimer.
1.13 + * 2. Redistributions in binary form must reproduce the above copyright
1.14 + * notice, this list of conditions and the following disclaimer in the
1.15 + * documentation and/or other materials provided with the distribution.
1.16 + * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
1.17 + * its contributors may be used to endorse or promote products derived
1.18 + * from this software without specific prior written permission.
1.19 + *
1.20 + * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
1.21 + * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
1.22 + * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
1.23 + * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
1.24 + * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
1.25 + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
1.26 + * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
1.27 + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
1.28 + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
1.29 + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.30 + */
1.31 +
1.32 +#ifndef Biquad_h
1.33 +#define Biquad_h
1.34 +
1.35 +#include <complex>
1.36 +
1.37 +namespace WebCore {
1.38 +
1.39 +typedef std::complex<double> Complex;
1.40 +
1.41 +// A basic biquad (two-zero / two-pole digital filter)
1.42 +//
1.43 +// It can be configured to a number of common and very useful filters:
1.44 +// lowpass, highpass, shelving, parameteric, notch, allpass, ...
1.45 +
1.46 +class Biquad {
1.47 +public:
1.48 + Biquad();
1.49 + ~Biquad();
1.50 +
1.51 + void process(const float* sourceP, float* destP, size_t framesToProcess);
1.52 +
1.53 + // frequency is 0 - 1 normalized, resonance and dbGain are in decibels.
1.54 + // Q is a unitless quality factor.
1.55 + void setLowpassParams(double frequency, double resonance);
1.56 + void setHighpassParams(double frequency, double resonance);
1.57 + void setBandpassParams(double frequency, double Q);
1.58 + void setLowShelfParams(double frequency, double dbGain);
1.59 + void setHighShelfParams(double frequency, double dbGain);
1.60 + void setPeakingParams(double frequency, double Q, double dbGain);
1.61 + void setAllpassParams(double frequency, double Q);
1.62 + void setNotchParams(double frequency, double Q);
1.63 +
1.64 + // Set the biquad coefficients given a single zero (other zero will be conjugate)
1.65 + // and a single pole (other pole will be conjugate)
1.66 + void setZeroPolePairs(const Complex& zero, const Complex& pole);
1.67 +
1.68 + // Set the biquad coefficients given a single pole (other pole will be conjugate)
1.69 + // (The zeroes will be the inverse of the poles)
1.70 + void setAllpassPole(const Complex& pole);
1.71 +
1.72 + // Return true iff the next output block will contain sound even with
1.73 + // silent input.
1.74 + bool hasTail() const { return m_y1 || m_y2 || m_x1 || m_x2; }
1.75 +
1.76 + // Resets filter state
1.77 + void reset();
1.78 +
1.79 + // Filter response at a set of n frequencies. The magnitude and
1.80 + // phase response are returned in magResponse and phaseResponse.
1.81 + // The phase response is in radians.
1.82 + void getFrequencyResponse(int nFrequencies,
1.83 + const float* frequency,
1.84 + float* magResponse,
1.85 + float* phaseResponse);
1.86 +private:
1.87 + void setNormalizedCoefficients(double b0, double b1, double b2, double a0, double a1, double a2);
1.88 +
1.89 + // Filter coefficients. The filter is defined as
1.90 + //
1.91 + // 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].
1.92 + double m_b0;
1.93 + double m_b1;
1.94 + double m_b2;
1.95 + double m_a1;
1.96 + double m_a2;
1.97 +
1.98 + // Filter memory
1.99 + //
1.100 + // Double precision for the output values is valuable because errors can
1.101 + // accumulate. Input values are also stored as double so they need not be
1.102 + // converted again for computation.
1.103 + double m_x1; // input delayed by 1 sample
1.104 + double m_x2; // input delayed by 2 samples
1.105 + double m_y1; // output delayed by 1 sample
1.106 + double m_y2; // output delayed by 2 samples
1.107 +};
1.108 +
1.109 +} // namespace WebCore
1.110 +
1.111 +#endif // Biquad_h
