[LAD] transfer function visualisation

Fons Adriaensen fons at kokkinizita.net
Sat May 26 16:45:30 UTC 2007

On Sat, May 26, 2007 at 06:02:35PM +0200, nescivi wrote:

> On Saturday 26 May 2007 16:09:35 Andrew Gaydenko wrote:
> > You are right, I'm just interested in what does this or that filter/effect
> > do (limiters, compressors, "tube-nizers" and so on - both software and
> > hardware). Of course, I see, say, attack/release times may be beyond such
> > simple db/db viewer. At any case "pseudo-static" mode is interesting also.
> > I imagine such viewer having (besides of excitation frequency control) 'min
> > level', 'max level' and 'excitation time' controls. Last one may be rather
> > long (say, up to 20-60 sec).
> I guess one could abuse Aliki for it. Instead of measuring the impulse 
> response of a room, just measure it of your JACK effect chain.

The assumption when emulating a system via its IR is normally that it is
linear and time-invariant. But it is possible to use the technique if these
conditions are not satisfied as well.

For non-linear systems there is a method based on Volterra series expansion.
To emulate such a system you convolve not only the input f(t) with the 
impulse response i_1 (t), but also f(t)^2 with i_2(t), f(t)^3 with i_3(t)
and so on. Can't remember from the top of my head how to find the i_n(t),
but it's possible. Farina has a paper on it.


Follie! Follie! Delirio vano è questo !

More information about the Linux-audio-dev mailing list