[PD] max value of last n samples

[Dario Sanfilippo]

I see what you mean, Roman. So you'd need the N-size block to be processed
beforehand, which would imply an N-size delay in the output, is that right?
I haven't thought of it, no idea whether that could be achieved by changing
the feedback period in the peak holder and/or adding a delay in the input.
Maybe I'll try something later.

Cheers,
Dario

On 3 February 2018 at 09:33, Roman Haefeli <reduzent at gmail.com> wrote:

> On Sam, 2018-02-03 at 02:47 +0000, Dario Sanfilippo wrote:
> > 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 moment.
> >
> > > 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:
>
>
> Yes, correct. If the peaks  reach the same level or are higher than the
> ones before, then the hold period is prolonged. But when they have less
> amplitude than the ones before, gaps appear. See:
>
> https://netpd.org/~roman/tmp/peakholder_gaps.png
>
> With a true max(x[0-(-N)], a downward stairway would appear and there
> wouldn't be any gaps.
>
> As I said, that is only small difference and for the purpose of a look-
> ahead limiter it probably doesn't matter that much.
>
> Roman
>
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