Re: [linux-audio-user] My MIDI latency is crap

On Fri, 2006-05-05 at 13:44 -0400, Lee Revell wrote:
> On Fri, 2006-05-05 at 12:32 -0500, Josh Lawrence wrote:
> > On 5/5/06, Lee Revell <rlrevell@email-addr-hidden-job.com> wrote:
> > > What is HZ set to in your kernel config?
> >
> > This is a new term to me. What does HZ mean, and how do I grep for it
> > in my kernel config?
>
> It's the kernel's internal tick rate and will determine the best
> achievable MIDI output latency. The default changed from 1000 (1ms
> ticks) to 250 (2.5 ms ticks) around 2.6.12, over the objections of the
> linux audio community.
>
> grep HZ /boot/config-`uname -r`
>
> or
>
> zgrep HZ /proc/config.gz
>
> if you have those files. It should be 1000 for optimal MIDI latency.
>
> I actually discussed this with Joachim from the MuSE team at LAC - we
> need a way for applications that need a low latency capable kernel to
> discover whether the kernel is good enough. One option would be to
> simply make MuSE depend on a "known good for audio" kernel in the
> package manager which is probably too aggressive, and not reliable
> enough. A better solution would be to have a simple, user friendly app
> that does a latency test and reports the results, and if a problem is
> found would recommend that the user upgrade the kernel, change some
> config options or file a bug report with their distro.
>
> Unfortunately it's a tricky problem, as you can see there's not even a
> distro independent way to check the kernel config.
>
> Lee

I'm pretty sure Josh is using Dapper Beta 2 with the stock i686 kernel
option, which is very likely set to HZ=y/1000, as the i386 kernel on
Dapper is.

Josh, did you recompile MuSE as you mentioned you were going to do?
Maybe there is a setting that you missed resulting in a sub-optimal
build? I'm not really familiar with MuSE at all, but if you're still on
Dapper's stock kernel, I think your issue might be elsewhere.

Have you tried routing into another app instead of MuSE (Seq24 for
example)?

Does your keyboard connect via USB or your soundcard or other MIDI I/O?

Dana