[linux-audio-user] Weird JACK behaviour w/ Qjackctl

Rui Nuno Capela rncbc at rncbc.org
Thu May 5 12:01:23 EDT 2005

>> > This "Auto refresh..." setup option is now well considered
>> > deprecated, if not harmful :) and should be off all the
>> > time nowadays. It is just some legacy option, among a few
>> > others, that persist from the early days--a time when my
>> > laptop was almost an unreliable piece of junk for realtime
>> > low-latency audio work.
>> Hehe, I guess you will remove this functionality in one of the
>> next versions :) .
> Why should it be off? Unless this refreshing the connections is
> accomplished a different way, it seems a very basic useability feature.

It should be off because you don't need to refresh the connections view
every so often, by issuing a graph query, moreover when it causes
deterministic glitches on the audio stream, which is a very-bad-thing.

Due to the callback nature of jack, all relevant events are being already
taken care of by qjackctl, and when they really happen (e.g. new clients
enters or exits the graph, new connections are made, etc.).

However, querying the graph is not a lock-free operation, and thus can
cause audible glitches. This is a current jack internal design issue.
Incidentally, Stéphane Letz has been working on an alternate lock-free MP
implementation, but still targeted on Mac OS X only.

So you better leave it, barely tolerable and only when there are effective
graph changes, which qjackctl traps and refreshes automatically thought.

Bye now.
rncbc aka Rui Nuno Capela
rncbc at rncbc.org

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