[linux-audio-dev] Re: LADSPA Extension for Extra GUI Data
drobilla at connect.carleton.ca
Sun Jun 25 16:21:20 EDT 2006
On Sun, 2006-06-25 at 18:57 +0100, Steve Harris wrote:
> On Sun, Jun 25, 2006 at 02:01:48 -0400, Dave Robillard wrote:
> > On Tue, 2006-06-20 at 08:35 +0100, Steve Harris wrote:
> > > On Tue, Jun 20, 2006 at 09:05:33 +1000, Loki Davison wrote:
> > > > Because people actually use them in Om, because people actually use Om
> > > > unlike certain other modulars. volt per octave is pretty damn obscure
> > > > in a computer program.... If i wanted to have a cutoff at concert A
> > > > what the hell is that in volts per octave?S
> > >
> > > Zero typically. I have to take issue with this, 1.0f per octave is the
> > > natural way to preresent things like filter cutoff in a modular. It's what
> > > makes the great modular systems so easy to work with.
> > Nonsense. As a numerical unit it has no meaning whatsoever, and the
> > unit actually used has no bearing on the user interface provided (which
> > should of course be exponential).
> It has a very specific meaning, +1.0 is +1.0 octaves.
so 2.0 is.. um... well, 2 octaves above.. uh, something... ;)
> > The only sane unit for frequency is Hz. As Loki said, if I want a
> > cutoff at concert A, I (like any musician) know that's 440Hz. Whatever
> > arbitrary ugly real number it is in "V/Oct As Defined By AMS" is not
> > something I or anyone else cares to know. Any table of frequencies, or
> > math app, or damn near _anything_ that deals with frequencies will
> > present it in Hz. If you can come up with a real reason why this
> > arbitrary "AMS V/Oct" makes any sense in a _digital_ modular, I'd like
> > to hear it.
> It's all about modulation, if I connect a [-1.0, 1.0] sine LFO to a cutoff
> modulation input then I want it to modulate up and down by N octaves, not
> N Hz, frequency-linearly symmetric modulations sound wrong. My favourite
> (digital) modular filters have a centre frequnecy (shown in Hz, expoentialy
> scaled control) and a modulation input that modulates in octaves.
> You want the modulation to be musically relevent, and the most musically
> useful unit for pitch is octaves :) Humans aren't SI sadly.
> I agree that describing it as volts is a bit odd, but it instantly makes
> people like me feel at home. There's not reason why a digital modular neds
> units for its modulation sources. It's just real numbers.
This is true, but there are other cases when you want a real, meaningful
frequency to do something with (using the same plugin). Eg lowpass all
frequencies above 800Hz. Someone working on a DAW definitely doesn't
want to deal with this meaningless V/Oct unit.
Of course, in a modular you can convert Hz frequencies to VOct
frequencies, and in a DAW you can convert VOct frequencies to Hz, but in
both cases it's a user nuisance, so it needs to be automatic. My gripe
isn't with the unit itself, so much as in the current situation with
LADSPA it's a really, really huge PITA to have a mess of twisty little
units, all alike.
Of course LV2 will let us solve this, and the frequency unit can in both
cases be kept entirely transparent by the host (if you want), making the
actual unit used by a plugin just an optimization as it should be
(skipping the conversion step).
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