I am trying to seperate Jack-Instances, one for Low-Latency monitoring with plugins loaded by Carla, and one “I dont care about latency as long as its compensated” instance for recording and on the fly mixing with Ardour. Each instance comes with a different buffer size and they are connected by zita-njbridge. I have a working setup as follows:
Hardware Jack Server, ALSA backend 48/2 samples, ~6ms roundtrip latency
Dummy Jack Server, Dummy Backend, 384/2 Samples, ~47ms roundtrip through the whole chain, including the Zita-Bridges and Hardware
Basically, it works as intended, its easy on the hardware but provides good latency for monitoring. The problem is I can not inform the Dummy-Jack about the additional latency (no -I or -O switch in dummy-mode), so Ardour cant compensate for it. I recorded the metronome through the whole chain and I get misaligned recordings by around 26ms, which corresponds to the additional latency by zita (2 times 10ms for in/out) plus 6ms coming from the Hardware-Jack. Recording only through the two zita-bridges results in the recording being 20ms late, just as expected.
Is there any way I can tell Jack in Dummy mode, or Ardour directly about the additional latency caused by zita and the other Jack?
Thanks in advance for any thoughts!
edit: I am using Ardour 6.3 and Jack 1.9.16 from the repos on Arch Linux.