character
chebyshev ripple	db (<0.0)
qfactor (resonator)	(>0.0)
frequency	Alpha Low Alpha Up or samplerate: Hz Lower corner Hz Midi note (69=A440) Upper corner Hz Midi note (69=A440)
more	matched z-transform (better off, check frequency response) prewarp (better on)
output	Signal bits (including sign): -1 bit saturation save brutal shift, this will remove shifts up to 4 positions by changing the factor, hence reducing accuracy by maximum 4 bits but more efficient calculation
execution


//Band pass butterworth filter order=4 alpha1=0.037453183520599 alpha2=0.063670411985019 
class  FilterBuBp4
{
	public:
		FilterBuBp4()
		{
			for(int i=0; i <= 8; i++)
				v[i]=0.0;
		}
	private:
		float v[9];
	public:
		float step(float x) //class II 
		{
			v[0] = v[1];
			v[1] = v[2];
			v[2] = v[3];
			v[3] = v[4];
			v[4] = v[5];
			v[5] = v[6];
			v[6] = v[7];
			v[7] = v[8];
			v[8] = (3.743561515783600305e-5 * x)
				 + (-0.64984203758803527062 * v[0])
				 + (5.22187801143368535151 * v[1])
				 + (-18.62939109557171590836 * v[2])
				 + (38.51794268736599491376 * v[3])
				 + (-50.46701448849155724474 * v[4])
				 + (42.90303533134298419327 * v[5])
				 + (-23.11211667933892854876 * v[6])
				 + (7.21544634991835387439 * v[7]);
			return 
				 (v[0] + v[8])
				- 4 * (v[2] + v[6])
				+6 * v[4];
		}
};