Re: [linux-audio-user] Control path in Om

From: Dave Robillard <drobilla@email-addr-hidden>
Date: Thu Oct 19 2006 - 02:27:02 EEST

On Sat, 2006-10-07 at 14:12 +0200, Thorsten Wilms wrote:
> On Sat, Oct 07, 2006 at 01:44:48PM +0200, Yves Potin wrote:
> >
> > Thank you very much, that's exactly what I was searching for. I've
> > found your plugin there :
> > http://lists.gnu.org/archive/html/om-synth/2005-11/msg00032.html
> > The result is here :
> > http://www.jazzcomputer.org/om.jpg
> > http://www.jazzcomputer.org/noise.om
> > As, without your plugin, I've spent much more than three or four
> > hours to do what I wanted without success, and found the solution in 5
> > minutes with it, I'd be very curious and interested to know how this can
> > be achieved in the « traditional » way in Om, i.e. controlling in time the
> > evolution of a filter with an envelope, which seems a somewhat common
> > use of a synth to me :).
>
> Ehm, just put Resonance (CR) to 0 and use Resonance (AR)?
> Lars was so nice to check this works out, even :)
>
> Otherwise use the 4 Pole Low-Pass Filter with Resonance (FARAIA).
>
> I would guess that you can get away with dynamic CR on resonance
> if the envelope isn't very fast / the change not that drastic.
> Otherwise artefacts can be expected.
>
> It would be great if the rate of ports could be switched, but
> LADSPA doesn't allow for this and LV2 might only with an
> extension.

Well, eliminating control ports (however much I would like to do so)
isn't realistic, however the LV2 spec does explicitly state that the
LADSPA phenomenon of "audio rate control ports" (eg CV) that break most
anything /except/ modulars (e.g. Ardour, Jack Rack) are NOT comformant.

In less confusing wording: audio ports MUST be.. audio!

So, these kind of ports will need to use a CV port extension, which
could (noone's written one yet) allow for both control or audio rate use
of the same port. This means all hosts will be able to use these
plugins and actually know what the (rough) purpose of the ports are.

Not ideal for a modular since those plugins with CR ports will still
exist, but a decent compromise, and surely a LOT better than the current
random situation that results in plugins that just mysteriously don't
work in certain hosts anyway.

It's a half solution to an only somewhat related problem, but at least
it's sane in LV2 instead of the complete mess of LADSPA in this dept.
At the end of the day the only solution to the old audio rate vs control
rate problem is writing more plugins.

-DR-
Received on Thu Oct 19 04:15:03 2006

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