[LAD] AMS to Ingen: VC to PCM

Aurélien Leblond blablack at gmail.com
Sun Sep 25 13:28:08 UTC 2011

>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!

By the way, the LADSPA plugins you are referring to, I suppose these
are the MCP ones?
Are you planning onto porting them to LV2 ones?


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