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 bessel filter order=3 alpha1=0.1 
class  FilterBeLp3
{
	public:
		FilterBeLp3()
		{
			for(int i=0; i <= 3; i++)
				v[i]=0.0;
		}
	private:
		float v[4];
	public:
		float step(float x) //class II 
		{
			v[0] = v[1];
			v[1] = v[2];
			v[2] = v[3];
			v[3] = (3.496555094616836390e-2 * x)
				 + (0.11336386147443269778 * v[0])
				 + (-0.61085794294029494012 * v[1])
				 + (1.21776967389651535889 * v[2]);
			return 
				 (v[0] + v[3])
				+3 * (v[1] + v[2]);
		}
};