[PD] max value of last n samples

Dario Sanfilippo sanfilippo.dario at gmail.com
Sat Feb 3 03:47:19 CET 2018

Thanks, Roman.

On 2 February 2018 at 21:28, Roman Haefeli <reduzent at gmail.com> wrote:

> On Fre, 2018-02-02 at 18:31 +0000, Dario Sanfilippo wrote:
> > There's an implementation of a peak holder in this blog post: http://
> > dariosanfilippo.tumblr.com/post/162523174771/lookahead-limiting-in-
> > pure-data. I remember testing it but please let me know if you find a
> > bug.
> Very nice write up. Thanks for sharing.
> > The current peak is replaced to whatever the input is after a desired
> > time, and the counter is reset whenever a new peak is found. It
> > should be easy to change it so that the peak is reset periodically.
> It's not exactly equivalent with what I've asked, since your
> implementation only takes new peaks into account after the hold period
> has ended.

​Perhaps my wording ​in the previous email was confusing: what happens is
that every new peak will update the output immediately, and whenever that
happens the countdown starts so that, should no other peak be detected
after that time, the output will be set to whatever the input is in that

> Assume an input signal consisting of a series of 1-sample
> impulses with a period that is slightly lower than the hold period. The
> output signal has a gap before each second impulse. For the use case in
> your article (which is also the use case I'm interested in), that
> doesn't matter much, because the peak holder signal is fed to a peak
> enveloper which somewhat masks those gaps.

​In that case, we should expect a full-amp DC​ out of the peak holder for
the impulses are faster than the hold time, and that's what we actually get:

[image: Inline images 2]

So the peak envelope is only used to transition from the peak to the
non-peak value exponentially.

> I'm going to use your implementation for peak holding. Thanks!
> Roman

​Sure, you're welcome. I hope that this makes more sense.


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