jackd:

[^rooker]

[PROBLEM]
I was trying to get jack (jackd) up and running, following the ubuntustudio+jack tutorial, but I ran into an unreasonable amount of XRUN problems:

18:17:57.198 Statistics reset.
18:17:57.206 Client activated.
18:17:57.282 Audio connection change.
18:17:57.303 Audio connection graph change.
18:17:57.314 XRUN callback (1).
18:17:59.304 XRUN callback (650 skipped).
18:18:01.331 XRUN callback (668 skipped).
18:18:03.356 XRUN callback (669 skipped).
18:18:05.381 XRUN callback (668 skipped).
18:18:07.408 XRUN callback (669 skipped).
18:18:09.432 XRUN callback (667 skipped).
18:18:11.455 XRUN callback (663 skipped).
18:18:13.614 XRUN callback (652 skipped).
18:18:15.631 XRUN callback (651 skipped).
18:18:17.655 XRUN callback (662 skipped).
18:18:19.687 XRUN callback (589 skipped).
18:18:21.711 XRUN callback (666 skipped).

Increasing the option "frames/period" from 64 to the initial value of 1024 slowed the rate of errormessages down, but they should actually not exist at all.

Opening any jack-aware application (e.g. jackbeat), led to strange program freezes.


[SOLUTION]
I was using the wrong ALSA device. Today's soundcards (even if you have only 1) have multiple input/outputs - and often they're even re-assignable, which is causing a lot of confusion.

In my case it was a C-Media CMI8738MC6 (5.1 onboard soundcard), having these output devices:

Code: Select all

hw:0 (The whole soundcard ???)
hw:0,0 (a switchable input/output - ADC/DAC)
hw:0,1 (2nd DAC)
hw:0,2 (digital output)

qjackctl offered several possibilities - defaulting to "hw:0" - it should have been the 2nd DAC (hw:0,1) - although hw:0,1 allowed playback, too. (strange, strange...)