Natty and the Real Time Kernel

ScottALavender at gmail.com ScottALavender at gmail.com
Wed May 4 13:00:38 UTC 2011


Hi Giuliano,

On May 4, 2011 7:40am, Giuliano Braglia <forevergyl at gmail.com> wrote:
> I've been browsing through old threads but i haven't been able to  
> understand...

> In natty (but also in maeverik, and I guess also in future upgrades)  
> there is no rt kernel available.


There are PPA's available with real time kernels available and I would  
expect even for Natty. I believe Falktx's PPA is one of these and well  
maintained at that.


> Would they work even without it? In Lucid I tried to start without  
> rtkernel and I had a lot of Xruns in Jack.



Absolutely you can start and run JACK well without a real time kernel.

I want to point out that a real time kernel is not a panacea, simply  
installing it will not make every system run perfectly. You still need to  
need to adjust your settings in JACK to accommodate your hardware. This  
might mean increasing your latency from 2.9msecs (for example) to 11.2msecs  
(for example) to find a stable latency without xruns.

Additionally, you did not specify how you installed your audio packages, ie  
if you did a fresh install from a Ubuntu Studio DVD or just added the  
packages to a vanilla Ubuntu install. If you did the later you will still  
need to add your user to the audio group and you should have installed JACK  
so that it could use real time privileges. Without these you would suffer  
performance degradation.

I should point out that using a -generic kernel does not preclude  
installing JACK with real time privileges. As noted above, I would advise  
that JACK have these privileges, even with the -generic kernel, or it will  
suffer poor performance and additional xruns.

I have found that the -generic kernel provides very acceptable stable  
latencies.

Regards,
ScottL
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