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


//Low pass butterworth filter order=2 alpha1=0.0022675736961451 
class  FilterBuLp2
{
	public:
		FilterBuLp2()
		{
			v[0]=0.0;
			v[1]=0.0;
			v[2]=0.0;
		}
	private:
		double v[3];
	public:
		double step(double x) //class II 
		{
			v[0] = v[1];
			v[1] = v[2];
			v[2] = (5.024142299431266101e-5 * x)
				 + (-0.98005250820633649234 * v[0])
				 + (1.97985154251435924166 * v[1]);
			return 
				 (v[0] + v[2])
				+2 * v[1];
		}
};