[LAD] ? jack/qjackctl XRUN info

[Rui Nuno Capela]

On Wed, July 11, 2007 03:27, Eliot Blennerhassett wrote:
> Greetings,
>
>
> what does it mean when I get messages like this in the qjackctl window?
> (or where should I look to find out)
>
>
> 14:21:16.546 XRUN callback (2 skipped).
> 14:21:23.026 XRUN callback (908).
> 14:21:24.594 XRUN callback (1 skipped).
> 14:21:27.767 XRUN callback (910).
> 14:21:28.617 XRUN callback (7 skipped).
> 14:21:30.632 XRUN callback (7 skipped).
>

A: jackd reports any kind of actual and potential overrun to its clients
through a callback mechanism. The above messages accounts for the number
of times the xrun callback function was issued from jackd to qjackctl,
which is obviously monitoring it. There's two kinds of messages:

... XRUN callback (N)
- this one reports the N-th occurence of a xrun callback since last reset.

... XRUN callback (N skipped)
- this one reports that N xrun callbacks have been issued since the last
time a XRUN callback message was displayed.

As said, these reports are issued by jackd and sure represent some kind of
problem, most of the cases are scheduling delays and jitter will be due
soon. Either the jackd parameters are too tight for correct and smooth
operation or you have a problematic system scenario.


>
> AFAIK I am not getting actual xruns - I don't get any message like this,
> and my audio sounds OK. **** alsa_pcm: xrun of at least 2721.798 msecs
>

This message occurs when the XRUN is detected at the ALSA backend, and
sure you will have lost audio data, so glitches will be certainly heard.


>
> The XRUN callbacks only happen when I use an alsa multi device (2 stereo
> substreams linked and synched together), not when I use a single stereo
> substream.
>

Oh well, so you're messing with a custom .asoundrc ? There's your systemic
problem. You'll need help from someone else which is more knowledgeable
about your specific setup: two soundcards? are they identical? how are
they synched? word-clock? yada, yada...

HTH
Cheers.
-- 
rncbc aka Rui Nuno Capela
rncbc at rncbc.org