I've been wondering how to emulate the normally connected effect send/return pair that is found in most pro mixing consoles in a patch that would function something like the diagram below:

The idea being that the signal path proceeds straight from inlet to outlet unless something is inserted to redirect the signal through another patch then back to the insert point and on to the outlet. This would seem to be a straight-forward task if it were possible to detect whether or not a connection exists to a specific inlet or outlet and then reroute the signal accordingly. Is this possible in Pd Vanilla? I've thought of a hack to reroute the original signal based on the presence of a signal at the return, but would prefer to base it on whether or not the connection exists instead.

Basically, I just want to expose interesting insert points in some patches for quick and easy application of discreet effects or processing without having to dig into their guts every time I want to add some reverb, delay, vibrato, or whatever.

Thanks,
P

@palaver As you are making the decision as to whether the insert should be live or bypassed I don't understand why you need signal detection.
I.E. on a real console..... you have plugged it in because you want it, or you haven't.
The bypass toggle can of course be sent a message from your master patch panel.
David.
insert.pd
Sorry, I have just modified that, as you need the toggle to have value 1 (bypassed) when the patch is started.

Thanks David. The only reason I considered signal detection was to avoid using a toggle. This is an exercise in pure laziness and interface design. Were there a method for detecting not signal, but a connection to an inlet, I would be where I want to be. Not strictly necessary by any means, just a convenience.

@palaver Ok...... sorry I was a bit snappy.
You could use [env~] for signal, but connection might be possible.
I can't remember straight away, but audio objects send a stream of zeros that could be detected?..... except [throw~] does not when a sub-patch has its audio switched off..... will have to sleep on that.
David.

I can't remember if there is an internal method to tell whether a connection exists or not.

In case there isn't, the challenge is being able to differentiate a silent connection from no connection. It's possible you could add small DC offsets to the outputs of processors and the inputs of insert points. Maybe insert points at +0.01 and processors at -0.01. You could run a snapshot~ and check every 100 milliseconds or so. If the input of the insert point reads 0.01, it is not connected. Then when connected, the processor would bring that down to 0.

I think I am missing something, I am nervous to post this.

"... the challenge is being able to differentiate a silent connection from no connection"

Good point, and exactly the thing that made me disfavor signal detection. I may well want to insert something that actually attenuates the signal, say like a volume pedal. By convention, I guess I could use an offset like you describe. I think I'd prefer a toggle at that point, considering the extra work adding the offsets would entail throughout my patches, but it is interesting to think about in any event. Thanks for tossing that idea out there.

@LarsXI Yes, I thought adding a small dc offset could work. The problem is that the 0 (connection) needs to be multiplied by the offset.... as all audio inlets add the two signals it needs a [*~] but that will not detect if the connection is removed as it will continue to multiply by zero.
It can be done if the same offset is applied to both sides of the connection, but of course any signal present on either side will falsify the result......... insert.pd
I have not found a way to test for zero yet. A change from no signal (zero) to signal zero will not trigger any audio logic objects.
David.

@palaver The zexy library as a [sigzero~] detector object. Dunno if you've been using that. I thought about adding a bias too, but it's equally un-elegant. I would think it would be a simple task to program an external that checks if an inlet has an external connection and output a bool, but I'm not versed in C nor the inner workings of PDs code.

I'm 90% sure that it is not possible to test for a connection in Vanilla. But if you don't mind using externals, then there is [iemguts/canvasconnections].