Ubuntu Studio 12.04 LTS Release

Ralf Mardorf ralf.mardorf at alice-dsl.net
Fri Apr 27 06:30:36 UTC 2012

On Thu, 2012-04-26 at 12:39 -0700, Len Ovens wrote:
> On Thu, April 26, 2012 12:19 pm, Ralf Mardorf wrote:
> >>  * Pulse Audio <-> JACK bridging enabled by default [snip]
> >
> > ... Bridging? = No issues for 10 IOs?
> There are issues with bridging and they get worse as the latency goes
> down. At -p 1024 there don't seem to be any problems. By -p 128 the bridge
> uses the same cpu % that jack uses. (on my machine jack is 5% at idle,
> with the PA-jack bridge 11%) By -p 32 the PA bridge uses double the cpu %
> that jack does. (jack at about 12%, jack with bridge 30% +)
> Our next trick will be to enable switching it off and on. PA uses very
> little cpu with bridging turned off. The main use (as I see) for PA-jack
> bridging is for recording the output of apps that are PA only. For example
> recording a phone interview on skype (I have heard a number of podcasts
> done like that). Any other use is really not needed. If one is watching
> youtube... they really don't need jack running at all. PA is just fine for
> that. In some ways it would be nicer to have it off by default and only
> turn it on when needed.
> My other comment is that the few times PA-jack is needed, it can probably
> be run at a higher latency anyway.

Thank you Len,

I didn't found information about the "algorithms [1]", sample accuracy,
and jitter, I just found
http://proaudio.tuxfamily.org/wiki/index.php?title=PulseAudio .
[1] Resampling? So we don't hear what we produce?
"app -> JACK (resample to 24/192) -> PulseAudio (resample to 16/44.1) ->
ALSA sound driver -> audio device" -


More information about the Ubuntu-Studio-devel mailing list