[Devel] CVPort and Ingen

[Stefano D'Angelo]

2011/10/3 David Robillard <d at drobilla.net>:
> 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.

True. Possibly need a lv2 port property for that?

> We *don't* want those to be backwards compatible, since we
> don't want such things showing up in CV naive hosts anyway.

lv2:optionalFeature vs lv2:requiredFeature.

(Let's try not to break this in two separate extensions, I'd say).

Stefano