Clicks with Jack even with large buffers

[DocDocDoc]

Hi there,

I want to use ZynAddSubFX live on stage. I got this Samson Graphite 25 MIDI/USB Keyboard. So far, wiring up stuff is not an issue for me... I use jackd.

However, no matter how large I set the buffers of both ZynAddSubFX and Jackd, there are some evil clicks every now and then. (I tried up to 1024 samples, the machine is an AMD Phenom Quad Core with Jack2 that distributes load accross cores. Soundcard is an RME Digi)

When I use OSS (with the aoss wrapper), I get pretty much the same high latencies but there are no clicks. The issue seems to be independent from the buffer settings altogether.

Any hints on what is going on?

Reasons for using jackd: a) I can't get the latency down enough b) On the machine I want to use live, I want other software to use the (stereo) audio output, too.

All the Best
DocDocDoc

[fundamental]

First if you don't already have one, make sure that you have a RT kernel installed, as that tends to make a night and day change in the xrun behavior.
Secondly, try to use --nperiods 3 as some hardware has a very very strong preference to this over the default of 2 periods.

As for issues on zyn's side, there are a number of things in the current release version which are not the safest and some of them have been corrected in the development mainline, while others have been fixed in one of the larger (and not release ready development branches).
Part loading from MIDI program changes for instance has only been made safe in the development branch, so it's not at all surprising if that operation results in some xrun.
As a general principle, make sure that you have an up-to-date version (going to the git master branch if you're comfortable with that) and things should preform fairly well (more-so with the UI disabled).

[DocDocDoc]

Don't get me wrong: There are no xruns in my jackd. The system operates with Ardour and loads tracks and of FX plugins without any flaws - even without major realtime stuff in the kernel.