[LAD] ALSA multi plugin and JACK xrun callbacks

Lee Azzarello lee at rockingtiger.com
Thu Dec 16 03:21:39 UTC 2010

Hello, I'm looking for some advice for an interesting symptom of
putting my M-Audio Fast Track Pro USB sound card into ALSA multi mode.
This sound card has four physical outputs which are mapped to two 2
channel ALSA streams rather than one four channel stream. I used the
ALSA multi plugin to combine these two streams into a single pcm
device so JACK can interface with all four outputs. It is working

Despite no perceptible problems in sound quality or latency, jackd is
printing hundreds of XRUN callback warnings to the message console
each second! I can operate the system perfectly fine, run multiple
applications, connect them to the four virtual outputs with no audible
timing issues.

What is the meaning of this many XRUN callbacks per second? What kind
of performance will this impact if not sound playback?

Thanks for your help,
Lee Azzarello

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