[Jack-Devel] I'm confused about latency

Fons Adriaensen fons at linuxaudio.org
Sat Apr 6 13:55:45 CEST 2019

On Sat, Apr 06, 2019 at 01:13:58AM +0200, Robin Gareus wrote:
> The case of a direct parallel bypass around a latent App1 like
>   HW Input] -> [App1] -> [App2] -> [HW Output]
>            `-----------^
> is really a constructed situation. JACK is not a modular synth, but a
> patchbay.

It's not really that far-fetched. I have this sort of situations all
the time.

Assuming the two inputs to App2 are mixed on a single Jack port, that
port will show different values for min and max latency.

Now is this a problem ? That depends on the actual use case. In many
cases it doesn't. 

To the OP:

*If* the different latencies matter, there are two solutions.

1. Insert a delay in the HW -> App2 connection.
2. Use separate inputs on App2, each will report its
   latency and App2 can compensate for the difference.

Note that 2. would be entirely automatic if App2 is designed
to do this. That is why Jack's latency reporting works the
way it does.



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