On 06/15, Dario Sanfilippo wrote:
>
> quad_osc(f) = tick ~ (_ , _)
> with {
> init = 1-1';
> w = 2*ma.PI*f/ma.SR;
> k1 = tan(.5*w);
> k2 = 2*k1/(1+k1*k1);
> tick(u, v) = omega-k1*(v+k2*omega) , v+k2*omega
> with {
> omega = (u+init)-k1*v;
> };
> };
another case when we need to initialize the delay line ;)
Dario, it is not that I suggest to change this code, please ignore,
but just for record... note that in this case we can avoid this hack
and write
quadosc(f) = tick ~ (_,_) : +(1),_ with {
k1 = tan(f * ma.PI/ma.SR);
k2 = 2*k1 / (1 + k1 * k1);
tick(u_0,v_0) = u_1,v_1 with {
tmp = u_0 - k1 * v_0;
v_1 = v_0 + k2 * (tmp + 1);
u_1 = tmp - k1 * v_1;
};
};
This generates a slightly better code. And, this allows to add (mem,mem)
quadosc(f) = tick ~ (_,_) : mem+1,mem with {
k1 = tan(f * ma.PI/ma.SR);
k2 = 2*k1 / (1 + k1 * k1);
tick(u_0,v_0) = u_1,v_1 with {
tmp = u_0 - k1 * v_0;
v_1 = v_0 + k2 * (tmp + 1);
u_1 = tmp - k1 * v_1;
};
};
to ensure that it always ouputs (1,0) at the very first tick. Not that I
think this is very important, but this matches other oscillators and looks
more clean imo.
Oleg.
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