[PD] removing clicks

[Chris McCormick]

On Mon, May 23, 2005 at 09:35:02AM +0100, matthew jones wrote:
> >filter which looks for discontinuities greater than a certain amplitude
> 
> Well at first that sounds just like a low-pass filter...
> Which would probably ruin the sound of the signal passing through it.

Yeah no, thought of that one - no good.

> Two things: you could write an abstraction/external to do a fancy 
> non-linear filtering, based on a threshold.  I think I remember seeing 
> stuff in Max related to this, like the 'temperature' of the signal which 
> was simply the difference between this sample and the last (..?).  So you 
> could possibly control the cutoff of the low-pass filter based on the 
> output of a 1-tap high-pass IIR filter that simply gave you the difference 
> between consecutive samples..  But this would bring plenty of difficulties 
> related to reaction speed and distortion.  Oh, but you know when it is 
> going to click..anyway..

This sounds a bit more like what I want. I want to filter out large
amplitude discontinuities in the signal without filtering all high
frequencies, especially not those of 'normal' amplitude.

> Secondly, the nicest approach would be to use windows (or envelopes) where 
> before you jump to a new place in the array, you begin fading in the new 
> position output (and fading out the old position output).  If you use 
> half-sine waves around 50ms in length as your windows then I would be 
> surprised if you ever heard any more clicks.

Cool, thanks for the idea. I'll do that if I can't get a discontinuity
detector working.

Best,

Chris.
-------------------
chris at mccormick.cx
http://mccormick.cx