[LAU] Testing JACK and PA latency

Len Ovens len at ovenwerks.net
Thu Sep 19 14:00:47 UTC 2013

On Thu, 19 Sep 2013, Fons Adriaensen wrote:

> Don't know - I'm by no means a PA expert... and I don't know
> your Jack period size. Given PA's reputation I'd expect more:
> 1024 samples would mean that PA imposes almost the same RT-
> requirements on apps as Jack does, and it was designed *not*
> to do that...  But maybe the jack <-> PA interface doesn't
> use the same amount of buffering that PA normally adds.

I am no expert either, but, if pa has access to an audio device that jack 
can get best latency of -p128 and jack is working with a device that can 
work with -p64... add pa-jack to the mix and jack will only work at -p128 
even with a device it could normally work at -p64 with.

Add to that the same -p128 device has problems with the wifi giving xruns 
forces those xruns across the pa-jack IF. If I turn that device off in pa 
tha problems go away. Also the amount of CPU time used by PA rises a lot 
when connected to jack.

Just my personal observations.

Len Ovens

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