linuxaudio.org

On Fri, 2011-03-04 at 15:24 +0100, Olivier Guilyardi wrote:

quoted text
> On 03/04/2011 01:53 PM, Stefano D'Angelo wrote:

> > Hence, in this case, I think we should exploit the

> > extensibility/decentralization of LV2: those who, like me, care about

> > "control rate" visualization hints may want to help on web UIs, for

> > example, the others might do the same with native GL.

> >

> > The only thing that we all need to ensure is that things work well

> > together, whatever the host/plugin author choice is, also trying to

> > make the whole thing as painless as it can be for everybody.

> >

> > Side note: this is yet another case where we could proceed to some

> > structured effort coordination at this point, but my feeling is that

> > this won't happen and the discussion will lead nowhere in the end.

>

> There is one thing which stays on my mind.

>

> I am familiar with developing JACK clients, not plugins. However, there has been

> quite a few discussions in the past where JACK was advocated as a way to create

> modules, DSP units dedicated to a specific task. In other terms: some kind of

> plugins.

>

> And what is absolutely nice about this is how it is non-intrusive. When working

> on a JACK client, there are only audio input and output ports, a thin transport

> layer, done. From these primitives, upon this bare but solid ground, a developer

> creativity enjoys a lot of freedom.

>

> However, there's been this critical and long-lasting session handling problem.

> Fortunately, this problem doesn't occur for LADSPA and LV2 plugins, since saving

> and restoring state is performed by the host.

>

> But, with this UI/engine separation, whenever a developer comes out with an

> innovative idea that he really likes, he's very likely to hit a wall because of

> a specific LV2 technical constraint. And at the same time it takes an incredible

> (if only possible) coordination effort to maintain LV2 to fulfill and

> *anticipate* all needs.

>

> But LV2 is extensible. So what I think is that in addition to the extensions

> which imply UI/engine separation (and I understand that it's important in many

> cases), there should be a DoWhatTheFuckYouWantInYourPlugin extension ;)

>

> With such plugins, restoring/saving state would rely on passing a blob in

> addition to restoring/saving the control ports values. There would be no such

> thing as UI/engine separation. The plugin would be self contained. And hopefully

> it would integrate nicely with other extensions such as midi.

>

> I think that this extension, since it would only imply simple but powerful

> primitives, would give a lot of freedom to developers who want that, and at the

> same time be rather easy to maintain.

You are mish-mashing way too many ideas into a big messy ball here for

me to address individually.
However, there is an extension a UI can use to get a pointer to a plugin

instance, which is mostly what you are talking about:
http://lv2plug.in/ns/ext/instance-access/
I do not recommend its use for any situation except where it is

absolutely necessary. Its role is either:
1) Temporary kludge used for necessary plugin <=> UI communication
2) A way to get direct access to waveform data for visualisation or

whatever, with graceful degradation where this is not possible
Use 1 is a big red flag that says something is missing and/or broken.

Use 2 is all good.
-dr
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