Mark Howell / biquad

Biquad filter library in C++ template form. On mbed LPC1768, can run about 100K operations per second with double precision float, or about 200K with single precision float.

Dependents:   EMG_Wiesje

biquad.h@3:abd20f34fd68, 2012-02-16 (annotated)

Committer:
mhowellaz
Date:
Thu Feb 16 00:07:57 2012 +0000
Revision:
3:abd20f34fd68
Parent:
2:9a9b643fcc66 

        

        
Who changed what in which revision?

        

            
                
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/*





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 *  biquad.h





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 *





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 *  Original source material from Robert Bristow-Johnson at 





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 *  http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt





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 *  and Nigel Redmon at http://www.earlevel.com/ 





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 *  





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 *  Derived from public domain C implementation by Tom St. Denis





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 *





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 *  Thanks gents!





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 *





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 *  C++-ification by Mark J. Howell





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 *





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 */





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#ifndef __BIQUAD_H_





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#define __BIQUAD_H_





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#include <math.h>





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#ifndef M_LN2





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#define M_LN2       0.69314718055994530942





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#endif





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#ifndef M_PI





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#define M_PI        3.14159265358979323846





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#endif





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/* formulation types */





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typedef enum {





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    DIRECT_FORM_I = 0,





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    TRANSPOSED_DIRECT_FORM_II





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} BIQUAD_FORMULATION_TYPE;





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/* filter types */





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typedef enum {





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    LPF, /* low pass filter */





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    HPF, /* High pass filter */





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    BPF, /* band pass filter */





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    NOTCH, /* Notch Filter */





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    PEQ, /* Peaking band EQ filter */





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    LSH, /* Low shelf filter */





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    HSH /* High shelf filter */





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} BIQUAD_FILTER_TYPE;





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template <typename T>





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class Biquad {





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public:





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    Biquad(BIQUAD_FILTER_TYPE type, 





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        T dbGain,  /* peak gain of filter */





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        T freq,  /* center frequency */





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        T srate,  /* sampling rate */





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        T Q, /* Q */





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        BIQUAD_FORMULATION_TYPE form = DIRECT_FORM_I);                       





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    void Reset(BIQUAD_FILTER_TYPE type, T dbGain, T freq, T srate, T Q, bool clearHistory = false, BIQUAD_FORMULATION_TYPE form = DIRECT_FORM_I);





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    void CalcCoefficientsDirectI(BIQUAD_FILTER_TYPE type, T dbGain, T freq, T srate, T Q);





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    void CalcCoefficientsTransposedDirectII(BIQUAD_FILTER_TYPE type, T dbGain, T freq, T srate, T Q);





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    T Calculate(T sample);





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    BIQUAD_FORMULATION_TYPE form;    





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    // used for DIRECT_FORM_1





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    T a0_I, a1_I, a2_I, a3_I, a4_I; 





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    T x1, x2, y1, y2;





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    // used for TRANSPOSED_DIRECT_FORM_II





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    T a0_II, a1_II, a2_II, b1_II, b2_II;    





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    T z1, z2;        





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};





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#endif





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