[music-dsp] Distortion algorithm query...

Ross Bencina rossb-lists at audiomulch.com
Wed Oct 3 03:12:15 EDT 2007


Andrew Simper wrote:
> An approach I'm looking at to bandlimit hard clipping is the same approach 
> I use to bandlimit oscillators. At the point of clipping you know the 
> derivative is zero, and the output level is 1 (for the positive side). If 
> you numerically compute the first and second order derivatives of the 
> audio signal at the clipping point you can introduce a band limited 
> corrective ramp and parabola which removes the first and second order 
> derivative discontinuities introduced by the clipping.

Hi Andy

That sounds rather interesting, but I'm not sure I understand what the 
corrective ramp and parabola look like.

So for example, in the ramp case, you know the gradient at the clipping 
boundary, so you could extend a ramp off to infinity to avoid a gradient 
discontinuity, but I guess that's not what you're doing... :-) so how does 
one construct a "bandlimited corrective ramp".

Thanks!

Ross. 



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