Reduce / identify latency in Linux sampler

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Reduce / identify latency in Linux sampler

Postby browny_amiga » Tue Sep 11, 2012 7:43 pm

Hi,

I have a M-Audio Keystation Pro 88 hooked up to a Linux system (Debian Squeeze) via USB and run Linux Sampler with a Bösendorfer B290 instrument. A friend played on the piano and told me that there is murderous high latency when playing. I have not noticed it, but problaby got used to it. I have noticed that in some ways, I enjoy playing on e-pianos much more, although they don't sound a third as good as my Bösendorfer Linux sampler duo.
Now I was wondering how to be able to measure latency, my mind is playing tricks on me when I play and sometimes I think I see the latency, sometimes I don't.
I also don't know where to start, as USB should not introduce any latency at all and neither should Jackd and Linux Sample. Where is the delay?

My friend told me that it seems to happen more when many voices are playing . I run this on a dual core 2.6 ghz system, with 8 GB of RAM and on a M-Audio 2496 Soundcard, which should be pretty high performance.

Since the Keystation Pro 88 does not have any instruments on board it self (no speakers, it is just a midi controler keyboard), there is no way to check it like that. Do you know any other ways? I am not currently using a real time kernel for Linux, would that help? But I figure the system should be fast enough for it.

Any pointers or ideas would be appreciated.

Markus
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Re: Reduce / identify latency in Linux sampler

Postby dakylla » Mon Sep 17, 2012 8:35 pm

hi man,

what are your jack settings (how do you start jack)?
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Re: Reduce / identify latency in Linux sampler

Postby varpa » Thu Sep 20, 2012 11:34 pm

From your description it is not clear you are using Jack (http:/ou /jackaudio.org/) which is a sound server for linux for professional audio work and which allows to set the latency (within the limit of your hardware). Generally, a latency below 10ms will not be noticable. The Ardour tutorial explains how to configure Jack: http://en.flossmanuals.net/ardour/ch015 ... on-ubuntu/ That example use QJackCtl which is a nice GUI interface to control Jack.
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Re: Reduce / identify latency in Linux sampler

Postby browny_amiga » Mon Sep 24, 2012 10:10 pm

Hi,

I use
jackd version 0.118.0

via
qjackctl, which is the GUI that you mention.

the parameters that jackd is started are these:
/usr/bin/jackd -r -dalsa -dhw:0 -r44100 -p1024 -n2

Kernel is:
2.6.32-5-686-bigmem #1 SMP Sun May 6 04:39:05 UTC 2012 i686 GNU/Linux
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