[LAU] Testing JACK and PA latency

Fons Adriaensen fons at linuxaudio.org
Fri Sep 20 19:08:37 UTC 2013

On Sat, Sep 21, 2013 at 04:07:32AM +1000, Patrick Shirkey wrote:
> I can hear the signal fine but I cannot hear or see the result of the
> signal after it comes back in the mic input. I could attempt to capture
> that part of the signal too for reference sake.
> If there are significant dropouts will that be the likely cause of the "??"

Depends on what you mean by 'dropouts' :-)
> I'm running jack with realtime capabilities but not a realtime kernel.

That should be fine. I haven't used a RT-patched kernel for years.

The loop via system:playback -> cable -> system:capture is only
there to give you the real round-trip latency, it doesn't have
any importance for examining this problem. You could just send
the signal from PA-sink directly to jack_delay.

Try to record the signal coming back from the PA-sink, e.g. using
timemachine. I'm pretty sure there will be discontinuities in the
recorded waveform.



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