On 12/19, Alik Rustamoff wrote:
>
> Today I tested all three. With last two svf filters I don't see any
> difference (I use ardour's built in plugin analyser), no noise.
> The noisy fi.highpass (the first one) becomes closer to them as cutoff
> freq goes higher, but still has different phase characteristics in lowest
> part of it's spectrum (0 to ~20hz)
Again, they should be equivalent but only in theory. In practice we have
the floating point issues.
Consider this trivial test-case:
F = 20;
process = no.noise
<: fi.highpass(2, F) - svf.hp(F, 1/sqrt(2))
: abs <: max ~ _;
lets check its output:
$ ./test-plot -n 100000 | tail -5
compiled with -quad option
2.98424785e-15
2.98424785e-15
2.98424785e-15
2.98424785e-15
2.98424785e-15
with -double
5.62450087e-12
5.62450087e-12
5.62450087e-12
5.62450087e-12
5.62450087e-12
with -single
0.00312119722
0.00312119722
0.00312119722
0.00312119722
0.00312119722
Oleg.
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