#include <math.h>
#include "Biquad.h"
#define M_PI 3.1415926535897932384626433832795f

//----------------------------------------------------------
Biquad::Biquad(long mode, float freq, float q, float fs)
{
	// Allocate sample buffers
	x1 = 0.f;
	x2 = 0.f;
	y1 = 0.f;
	y2 = 0.f;

	// Initial filter attributes
	this->mode = mode;
	this->freq = freq;
	this->q = q;
	this->fs = fs;
	coefs();
}

//----------------------------------------------------------
void Biquad::setFreq(float freq)
{
	this->freq = freq;
	coefs();
}

//----------------------------------------------------------
void Biquad::setQ(float q)
{
	this->q = q;
	coefs();
}

//----------------------------------------------------------
void Biquad::setMode(long mode)
{
	this->mode = mode;
	coefs();
}

//----------------------------------------------------------
void Biquad::setFs(float fs)
{
	this->fs = fs;
	coefs();
}

//----------------------------------------------------------
void Biquad::process(float* input, float* output)
{
		// Calculate filtered value
		output = b0 * input + b1 * x1 + b2 * x2 - a1 * y1 - a2 * y2;

		// Shift sample history
		x2 = x1;
		x1 = input;
		y2 = y1;
		y1 = output;
}

//----------------------------------------------------------
void Biquad::coefs()
{
	// Precalculate some stuff
	float w0 = freq / fs * 2.f * M_PI;
	float sin_w0 = sin(w0);
	float cos_w0 = cos(w0);
	float alpha = 0;
	if (mode == fmodeHP || mode == fmodeLP)
	{
		alpha = sin_w0 / (2.f * q);
	}
	else if (mode == fmodeBP || mode == fmodeBS)
	{
		alpha = sin_w0 * sinh(log(2.f) / 2.f * q * w0 / sin_w0);
	}
	// Highpass
	if (mode == fmodeHP)
	{
		b0 = (1.f + cos_w0) / 2.f;
		b1 = -(1.f + cos_w0);
		b2 = (1.f + cos_w0) / 2.f;
		a0 = 1.f + alpha;
		a1 = -2.f * cos_w0;
		a2 = 1.f - alpha;
	}
	// Lowpass
	else if (mode == fmodeLP)
	{
		b0 = (1.f - cos_w0) / 2.f;
		b1 = 1.f - cos_w0;
		b2 = (1.f - cos_w0) / 2.f;
		a0 = 1.f + alpha;
		a1 = -2.f * cos_w0;
		a2 = 1.f - alpha;
	}
	// Bandpass
	else if (mode == fmodeBP)
	{
		b0 = alpha;
		b1 = 0.f;
		b2 = -alpha;
		a0 = 1 + alpha;
		a1 = -2.f * cos_w0;
		a2 = 1.f - alpha;
	}
	// Bandstop
	else if (mode == fmodeBS)
	{
		b0 = 1.f;
		b1 = -2.f * cos_w0;
		b2 = 1.f;
		a0 = 1.f + alpha;
		a1 = -2.f * cos_w0;
		a2 = 1.f - alpha;
	}
	// Flat
	else if (mode == fmodeFlat)
	{
		b0 = 1;
		b1 = 0;
		b2 = 0;
		a0 = 1;
		a1 = 0;
		a2 = 0;
	}
}


********************* the error ***********************

I:\Program Files\Microsoft Visual Studio 8\VC\include\biquad.cpp(54) : error C2297: '*' : illegal, right operand has type 'float *'
I:\Program Files\Microsoft Visual Studio 8\VC\include\biquad.cpp(58) : error C2440: '=' : cannot convert from 'float *' to 'float'
        There is no context in which this conversion is possible
I:\Program Files\Microsoft Visual Studio 8\VC\include\biquad.cpp(60) : error C2440: '=' : cannot convert from 'float *' to 'float'
        There is no context in which this conversion is possible