Ubuntu Studio 12.04 LTS Release

Len Ovens len at ovenwerks.net
Thu Apr 26 19:39:18 UTC 2012

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.

Len Ovens

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