"Allow feedback in routing" causes delay

[politcat]

why does Allow feedback in routing cause a delay?

it's kind of difficult to explain the setup so here's a project to download

do this:

--open the project and make sure Allow feedback in routing is on

--insert a plugin with PDC on track 4 (like a T-rackS plugin)

--play the project for 10 seconds or so to hear the delay

--hit stop. either turn off Allow feedback in routing or disable the plugin with PDC

--hit play again and the delay is gone

[EricM]

Audio feedback routing needs to cause a delay, otherwise the latency
could diverge. So that is normal and proper behavior.

There are however issues with midi/audio routing being treated the same:

http://forum.cockos.com/showthread.php?t=40686
http://forum.cockos.com/showthread.php?t=75202

Vote here:
http://forum.cockos.com/project.php?issueid=2722

e

[politcat]

so how do I make the sends routing in my little project work w/o delay?

(did you download it?)

[EricM]

I just did, I see you are looping one bar and the
latency introduced by feedback delay accumulates
over many loops (possibly a bug with looping&feedback?).

Not sure how this is significant or problematic
to any real world application though, as when you
duplicate snares over timeline and play lineary
the feedback delay remains constant.

e

[politcat]

Originally Posted by EricM

Not sure how this is significant or problematic
to any real world application though

I can assure you a real world application is at issue or I wouldn't start this thread. I'm not just fooling around with reaper

it's nothing to do with a looping snare. that project was for demonstration purposes only

[EricM]

Originally Posted by politcat

I can assure you a real world application is at issue or I wouldn't start this thread. I'm not just fooling around with reaper

I wasn't implying anything regarding your work
with reaper, I just hoped you would provide info
on the real life app as I have no clue what could
it be.

e

[politcat]

let me try again

track 1 is a vocal, snare, whatever sending to track 4, which has a reverb (with PDC) inserted

track 1 also sends to tracks 2 and 3 which are a delay feeding back to itself

if I create a send from track 2 to 4, the send from track 1 to 4 will clearly no longer be in time

[EricM]

Ok I see what your issue is:

You have another signal that is also processed with
feedback routing sent to reverb, which ruins the PDC
of all signals sent to the reverb.

This one is a bit tricky and a special case, only the
Devs can give you the right answer, but the implementation
of feedback routing is probably done so that all tracks
connected to it stop plugin delay compensation in order
to prevent latency divergence.

Hope the devs or someone more code savvy will give you
an answer if this could have been resolved in this case.

I was thinking of proposing a solution to manually compensate
for latency by using timedelay plug-in on track 4, but the
plug-in itself relies on PDC to introduce negative time offset
so it won't work.

e

[politcat]

in this case it would be great if ReaDelay would feedback into itself to create the natural decay

that would be a cool update for ReaDelay