[linux-audio-user] XRUN/XRUN callback

[Rui Nuno Capela]

Andres Cabrera wrote:
> Hi all,
> I'm wondering if anyone can explain the difference between an XRUN, and
> an XRUN callback. Is an XRUN callback not a matter of great concern? (It
> seems to me from reports in the qjackctl message window that no time is
> actually lost). On my system at 11ms latency i get an XRUN callback
> every 30 minutes or so and a true XRUN when something happens (open a
> jack application, for instance).
>

Qjackctl has two (2) codepaths to detect and report XRUNs.

One is optional and klunky, and probably still featured only for
historical reasons (!). That's this method of capturing all jackd's
stdout/stderr output and parsing it for the literal XRUN text message. As
it seems, this must be what you call a "true" XRUN, and appears on the
qjackctl messages windows colored in bright red (but with no timestamp).

The second one uses the JACK API, by registering a proper XRUN callback
procedure. That is the official way in which the jackd server notifies
registerd clients of a XRUN occurrence. This one appears on the qjackctl
messages window as a "XRUN callback" (pink?) message, prefixed by a
timestamp and includes a callback counter, which is also shown on the main
display--it's the number shown between the "(" and ")" if you didn't
noticed.

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