[ardour-dev] issues with plugin in/out counts

nolv nolv at free.fr
Wed Nov 24 12:35:39 PST 2004

I'll try to give a different answer, which comes from the constation 
that any choice ardour can make about streams and connections, there are 
many chances that the user wants something different. So here is my 

In the absence of plugin. The number of streams is determined by the 
number of inputs, right?
I think there is no reason for changing this, even in the presence of 

Let's see it through the example:

>the problem is that it rapidly leads to untenable situations. consider
>what happens if you add a mono plugin to a track with 1 input. The
>plugin is not replicated - there is no need to. so far, so good.
>now the user wants to add a 1in/2out plugin, for example most
>reverbs. no problem still, as long as they are ordered in the same
>order as they were added.
In that case, up to now, ardour create a second stream, and a second 
panner. Something is unclear for me here: is there again a single 
instance of the gate? Or are there two instances sharing one gui? I 
mean: are there two streams all along the signal flow of this track, or 
only starting from the reverb outputs?

Anyway, if the user decided this track to be a mono track, maybe there 
is a good reason, maybe not, but maybe. Then I suggest ardour do do 
nothing, keep one stream and inform the user he did something ambiguous 
and  might prefer a stereo track (bring a popup window with ok button). 
If he wants a stereo track, he has just to add an input. Ardour might 
hence offer the possibility to change the mono/stereo/n-channel 
configuration of any track at any time, by adding/removing input/output 
connections. For now it is impossible, only adding is possible.

That answers to the question "how many streams?".

Now : "what to do with 1in/2out plugins?"
Again, the user might want to choose the answer.

In the 1-stream case, there is no ambiguity for the single input but 3 
possibilities for the outputs :
- mixed
- only left go to next stage
- only right
Why not adding a drop down list in the plugin ui with these three choices?
For Gerard, we could add these two:
- only left, the right output becomes a jack port
- only right, the left output becomes a jack port

In the 2-streams case, there is no ambiguity for the outputs and also 3 
(or 5) possibilities for the input:
- a mix of left and right output of previous plugin
- only left input
- only right

Finally, we could do this... hem, you could, sorry, i have no idea how 
to code this :)

* The number of streams is unambiguously determined by the number of 
inputs, the user must have control over it by adding/removing input ports.

* Any time in the signal flow inputs and outputs of the plugins are not 
in agreement, give the user the choice of what to do. Warn him(her) 
anytime he(she) is doing something ambiguous, and let him(she) know that 
a default config has been done (mixing L/R or anything else, this could 
be decided in the options editor). Invite him(her) to look at the in/out 
config of the plugins.

* Two drop-dow lists are added in the plugin UI. Plugin N-1 output 
shares the same list with plugin N input. If there is no ambiguity, the 
drop-down list is greyed.

I agree that in a n-inputs/m-outputs world, the number of possibilities 
can become huge! But at least there exists a simple algorithm to find 
them all!

This way, any plugin could fit in any  track!

Does it make sense?

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