desc: Peak/Notch filter  (Mono)

slider1:0<0,1,0.001>cut
slider2:0<0,1,0.001>steep
slider3:0<0,1,1{peak,notch}>filter type
slider4:0<-24,24,1>gain

@init
outp=0;
outp1=0;
outp2=0;
pi=22/7;

@slider
r=slider2*0.99609375;
f=cos(pi*slider1);
a0=(1-r)*sqrt(r*(r-4*(f*f)+2)+1);
b1=2*f*r;
b2=-(r*r);
ftype=slider3;

gain=10^(slider4/20);

@sample
inp=0.5*(spl0+spl1);

outp=a0*inp+b1*outp1+b2*outp2+p4;
outp2=outp1;
outp1=outp;
ftype==0?( 
result=outp; //peak
):(
result=inp-outp; //notch
);

spl0=result*gain;
spl1=result*gain;