/*
* 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 * /
* notice , this list of conditions and the following disclaimer .
* 2 . # define Biquad_h
* notice , this list of conditions java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0
* 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
* DISCLAIMED . IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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* ( INCLUDING , BUT NOT LIMITED TO , PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES ;
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* THIS SOFTWARE , EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE .
* /
# 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 ( ) = default ;
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
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