[LAD] AMS to Ingen: VC to PCM
d at drobilla.net
Sun Sep 25 21:01:30 UTC 2011
On Sun, 2011-09-25 at 14:28 +0100, Aurélien Leblond wrote:
> >1. Audio in/out ports. These are just blocks of samples, same
> > as e.g. Jack buffers. Some call this 'PCM' but that is a
> > misnomer.
> >2. Control in/out ports. These are technically identical to
> > audio ports (full sample rate), but the signals carried
> > on them are normally not meant to be audio. How they are
> > interpreted depends on the module and the particular port.
> > Frequency control inputs can be linear or log, in the latter
> > case that means 1/octave. Gain controls can be linear or log,
> > there is AFAIK no fixed conversion factor for the latter. For
> > example the VCA module uses 80dB/1 in exponential mode, but
> > other gain controls may be different.
> > Control ports are audio rate, but most modules/plugins subsample
> > some or most of them. They either just use the first value in a
> > block, or recompute internal paramters based on the last value
> > in a block and then interpolate them linearly.
> > Since control signals are (at least officially) at audio rate,
> > LADPSPA plugins designed to be used in AMS (e.g. mine) will
> > declare their control inputs as audio inputs.
> Thanks, I think it makes things way clearer!
> What's confusing me so far is that I ported the VCO2 module, but with
> exactly the same setup, the VCO2 LV2 in Ingen sounds out of tune
> compared to the one in AMS. I thought it was due to some kind of
> needed convertion, but maybe I'll go back to my code to double check I
> didn't make any mistakes!
The note builtin in Ingen uses Hz for frequency. Anything else is
completely insane :)
There is a converter plugin in 'omins' which I need to port to LV2 as
well one of these days...
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