Hi Everyone!,

We've just registered to the forum and we're relatively new to the PD world.

We're working on our own patch and we are having big issues with the midi implementation.

Basically we have created a filter and we would like to control the center frequency with a knob linked to a midi controller.

The problem is that of course the midi accepts just 127 messages but we need to translate them into the audible frequency range.

We have tried using this object [expr $f1 * (20000/127)] but it gives an exponential result instead of a linear one (plus step's jumps between frequencies are audible).

So we were wondering if you could help us anyhow with some tips...

It might sounds as a really stupid and silly question but as We said before we're novices.

Thanks in advance,

IASM

http://www.pdpatchrepo.info/hurleur/filters_for_forum.pd

@IASM said:

We have tried using this object [expr $f1 * (20000/127)] but it gives an exponential result instead of a linear one (plus step's jumps between frequencies are audible).

That is definitely linear on the frequency scale. If you mean linear in terms of pitch, then [mtof] is what you want, but that appears to be what you're using in the patch.

The clicks in the steps are a problem of the filters themselves. They message-rate inlets instead of audio for the frequency. When the frequency is updated, it jumps to that value, causing the filter to click. And since the inlets don't take audio signals, you can't smooth them with [line~].

You can use [vcf~] instead of [bp~] to fix that with the bandpass section. There aren't built-in alternatives for [lop~] and [hip~], but I made abstractions of them:

http://puredata.hurleur.com/viewtopic.php?pid=23018#p23018

You can also check out some of the libraries in Pd-extended, particularly iemlib, for some more filters.