As I reported previously, I got excellent latency several years ago with Csound on Ubuntu (previous version) with ALSA hardware drivers. The stable latency was essentially the same as what I got on the same notebook computer with Windows XP Media Edition and ASIO drivers: anywhere from 2.5 to 5 milliseconds. I don't recall doing a blessed thing to the kernel. Maybe I should try this again with current Csound.

Regards,
Mike

-----Original Message-----
>From: Andres Cabrera 
>Sent: May 10, 2008 8:13 AM
>To: csound@lists.bath.ac.uk
>Subject: [Csnd] Re: Re: Re: Finding out where latency is
>
>Hi Felipe,
>
>I mean using the preemptive option in the kernel (I think for kernels before
>around 2.23 you needed to apply the rt patches to get the preemptive
>option). I think a part of the rt patches was merged recently into the
>mainline kernel, but there's probably still some improvements from the rt
>patches (I haven't built my own kernel in a while, so I'm not sure about the
>current state).
>But anyway for jack to work wihtout xruns you definetely need a preemptive
>kernel and the realitme-lsm module (to allow apps to get realtime privileges
>without being root). This information may also be out of date as well =)
>If you have this jack will probably work excellent.
>Cheers,
>Andrés
>
>On Fri, May 9, 2008 at 2:22 PM, Felipe Sateler  wrote:
>
>> On Friday 09 May 2008 14:47:07 Andres Cabrera wrote:
>> > Hi Felipe,
>> >
>> > Are you using Jack (that's the best bet for low latency audio on linux,
>> and
>> > will usually give very good latencies even with built in cards on old
>> > laptops)? If so, do you have an RT kernel?
>>
>> I haven't been able to get jack working properly (lots and lots of xruns).
>> Apparently my soundcard (sigmatel high definition audio) is not very well
>> supported.
>> What kernel config option is that? My kernel is not preemptive. Or are you
>> talking about a RT patchset?
>>
>>
>> --
>> Felipe Sateler
>>
>
>Send bugs reports to this list.
>To unsubscribe, send email sympa@lists.bath.ac.uk with body "unsubscribe csound"

--- Felipe Sateler  wrote:
> It seems that jack is more picky than csound. Jack keeps
> giving me these 
> absurdly repetitive and high xruns:
> **** alsa_pcm: xrun of at least 1210438687653.888 msecs
> 
> Which if I did my math right is about 7 years.

Maybe it's reading the bits on a negative number wrong ...
meaning, of course, the signal might have arrived 0.112
milliseconds BEFORE it was sent.  If so, Jack can travel faster
than light -- and the noise you hear is just from synths in
nearby parallel universes ;-)

Seriously, though, I've been running JACK + the rt preempt
kernel from Ubuntu for a few months, now.  The biggest factor
I've found to cause problems is GUI resources hogging the cpu. 
For example, on KDE, hovering over the window selector makes
this help balloon fade in with a list of the active programs on
that desktop.  Every time this happened, I saw an xrun.  So I
went to the control center and turned off most of the desktop
effects -- bingo, low latency.

It was worse on my wife's laptop, even though she has a faster
processor.  Why?  Her screen is much bigger (in terms of
resolution).  So I find myself having the lowest latency on this
ancient computer of mine with its pathetic video card -- a place
where the sound card doesn't really have a strong competitor for
cpu attention!