[Devel] CVPort and Ingen

David Robillard d at drobilla.net
Sun Oct 2 19:52:45 PDT 2011

On Sun, 2011-10-02 at 19:33 -0400, David Robillard wrote:
> On Sun, 2011-10-02 at 09:22 -0500, Gabriel Beddingfield wrote:
> > On 10/02/2011 06:36 AM, Aurélien Leblond wrote:
> > > Hi,
> > >
> > > I am trying to use the CVPort for my VCO, but don't seem to be able to
> > > load it in Ingen.
> > 
> > Ingen probably doesn't support the CVPort, yet.
> Indeed it does not.
> As brought up on l-a-d by Stefano D'Angelo, it should be possible to
> make backwards compatible CV ports by still using the type
> lv2:ControlPort, but then providing some mechanism for the host to
> indicate the port is, in fact, connected to an audio buffer.

On second thought, there is a use case for both of these appropaches
(i.e. they are not mutually exclusive):

Some CV ports are just like controls (e.g. something a user might
twiddle), but can be modulated at audio rate.  These we want to be
backwards compatible with lv2:ControlPort in CV naive hosts.  An example
is the cutoff parameter of a low-pass filter.

Others are "CV only", and only really intended for modulation and don't
make sense to present to a user as a control.  The trigger/gate input
and envelope output of an ADSR envelope is a good example of this kind
of port.  We *don't* want those to be backwards compatible, since we
don't want such things showing up in CV naive hosts anyway.


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