[LAD] AMS to Ingen: VC to PCM

Aurélien Leblond blablack at gmail.com
Mon Sep 26 13:37:00 UTC 2011

On Sun, Sep 25, 2011 at 10:01 PM, David Robillard <d at drobilla.net> wrote:
> 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...

Hi David,
Could you let me know where in Omins it is?
I can port this for you... One plugin to create won't kill me (and I
start to enjoy it anyway!)


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