[sdiy] BLIT/BLEP virtual analogue synthesis

[Thomas Strathmann]

Am 8/4/10 20:49 , schrieb Olivier Gillet:
>> Low-pass-filtering might or might not be linear, but bandlimiting (aka
>> brickwall filter) most certainly isn't.  It is defined as an aperture
>> function in the spectral domain which produces an infinite, non-causal
>> impulse response in the time domain, so it isn't even realizable.  That's
>> what all the fuzz with window functions is about (and BLIT/BLEP also use
>> them for their bandlimited waveforms).
>
> Hmmm, how can this prevent it from being linear? It might be a
> convolution by a non-causal, non-bounded support thing, but it's still
> a convolution, isn't it?

Ideal lowpass filtering is linear, just not realizable because because, 
as you say, the impulse response of the filter (sinc function) is 
non-causal.

	Thomas