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

Committer:
mhowellaz
Date:
2012-02-14
Revision:
0:f8ed62dbacbc
Child:
1:9c0546cd518e

File content as of revision 0:f8ed62dbacbc:

/*
 *  biquad.cpp
 *
 *  Original source material from Robert Bristow Johnson at 
 *  http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
 *  
 *  Derived from public domain C implementation by Tom St. Denis
 *
 *  Thanks gents!
 *
 *  C++-ification by Mark J. Howell
 *
 */

#include <math.h>

#ifndef M_LN2
#define M_LN2       0.69314718055994530942
#endif

#ifndef M_PI
#define M_PI        3.14159265358979323846
#endif

/* filter types */
typedef enum {
    LPF, /* low pass filter */
    HPF, /* High pass filter */
    BPF, /* band pass filter */
    NOTCH, /* Notch Filter */
    PEQ, /* Peaking band EQ filter */
    LSH, /* Low shelf filter */
    HSH /* High shelf filter */
} BIQUAD_FILTER_TYPE;

template <typename T>
class Biquad {

public:
    Biquad(BIQUAD_FILTER_TYPE type, 
        T dbGain,  /* gain of filter */
        T freq,  /* center frequency */
        T srate,  /* sampling rate */
        T bandwidth); /* bandwidth in octaves */
        
    void Reset(BIQUAD_FILTER_TYPE type, T dbGain, T freq, T srate, T bandwidth);
    
    T Calculate(T sample);
    
    T a0, a1, a2, a3, a4;
    T x1, x2, y1, y2;

};