PA-jackd bridging

Len Ovens len at
Sat May 26 18:29:25 UTC 2012

Some things I have found out about PA-jackd bridging.

 - If PA is running and then Jackd is started, PA must be reconfigured to
continue working. Anything currently using PA for its output will stop
until this is done. I assume inputs is the same thing, but really, if you
are recording why would you make such changes in the middle of a

 - Jackd's latency setting affects PA's CPU usage as PA works to keep up
with jackd. However, this doesn't seem to be a problem on most modern
(and some less modern) systems.

 - PA also has an effect on jackd. This is very noticeable if there are
two (or more) audio interfaces. If one IF has a higher limit for latency,
that limit will be forced on the other card even though it can normally
run at a lower latency. If that IF has stability issues those will also
show up on the second card even though it normally would be fine.

I would not consider any of these things bugs.

I do think there needs to be some thought about how US is shipped though.
PA-jackd bridging does not just work out of the box. It does not appear
that it can unless jackd is started with the session. In this case PA can
be configured with all IF "off". So if jackd is stopped to changed setting
for example, PA will not grab the port. It will however create a "dummy"
IF and switch any current applications to that port. It does not
automatically switch them back when jackd restarts.

Any other ideas?

Len Ovens

More information about the Ubuntu-Studio-devel mailing list