[LAU] Jack gives xruns with alsa driver, but dummy driver + alsa_in/out doesn't

Jeremy Salwen jeremysalwen at gmail.com
Thu Apr 21 17:57:29 UTC 2011


Hi All,

I'm having a very strange problem setting up Jack.

I have a card which aplay -l lists as

card 0: SB [HDA ATI SB], device 0: ALC892 Analog [ALC892 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: SB [HDA ATI SB], device 1: ALC892 Digital [ALC892 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

I'm only interested in the analog outputs.

when I start up jackd (from qjackctrl), I am offered three different options
for my sound interface:

hw:0     HDA ATI SB
hw:0,0  ALC892 Analog
hw:0,1  ALC892 Digital

(input devices are similar)

However, when I start up jackd, I get a constant stream of xruns.  This is
true regardless of what combination of input and output hardware device I
choose, as well as real-time settings and period size (I obviously haven't
tested everything, but a large representative swath).

On the other hand, if I choose plughw:0, jackd gives me a warning, but I can
get zero xruns and no artifacts for as low as 128 frames/period.

Similarly, if I start jack with the dummy driver, and then run alsa_in, I
can get down to 32 frames/period with no artifacts nor xruns.

What could be going on?

Thanks,
Jeremy
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