[LAU] Testing JACK and PA latency

Fons Adriaensen fons at linuxaudio.org
Fri Sep 20 15:12:59 UTC 2013

On Fri, Sep 20, 2013 at 08:41:10PM +1000, Patrick Shirkey wrote:
> On Fri, September 20, 2013 8:31 pm, Fons Adriaensen wrote:
> > On Fri, Sep 20, 2013 at 06:59:06PM +1000, Patrick Shirkey wrote:
> >
> >>  33114.906 frames    689.894 ms total roundtrip latency
> >> 	extra loopback latency: 32922 frames
> >> 	use 16461 for the backend arguments -I and -O ??
> >
> > Note the '??', it means the measurement is not reliable,
> > probably due to skipped cycles (i.e. phase discontinuity).
> >
> xruns?

Assuming you're measuring a 'clean' channel, the ?? most probably
mean a discontinuity in the signal seen by jack_delay. In the
sense that part of signal was 'jumped over' - a short gap that
preserves the timing would not have any effect. This happens
when Jack skips one or more cycles, and this in turn can be
the result of an xrun (also of other things, but not in this
case). Is your Jack running RT ?



A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

More information about the Linux-audio-user mailing list