biquad.h

////////////////////////////////////////////////////////////////////////////
//                           **** BIQUAD ****                             //
//                     Simple Biquad Filter Library                       //
//                Copyright (c) 2021 - 2022 David Bryant.                 //
//                          All Rights Reserved.                          //
//      Distributed under the BSD Software License (see license.txt)      //
////////////////////////////////////////////////////////////////////////////

// biquad.h

#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <math.h>

typedef struct {
    float a0, a1, a2, b1, b2;
} BiquadCoefficients;

typedef struct {
    BiquadCoefficients coeffs;  // coefficients
    float in_d1, in_d2;	        // delayed input
    float out_d1, out_d2;	// delayed output
    int first_order;            // optimization
} Biquad;

#ifdef __cplusplus
extern "C" {
#endif

void biquad_init (Biquad *f, const BiquadCoefficients *coeffs, float gain);

void biquad_lowpass (BiquadCoefficients *filter, double frequency);
void biquad_highpass (BiquadCoefficients *filter, double frequency);

void biquad_apply_buffer (Biquad *f, float *buffer, int num_samples, int stride);
float biquad_apply_sample (Biquad *f, float input);

#ifdef __cplusplus
}
#endif