On Tue, 18 Jun 2013, aCOSwt wrote:
> Hello,
>
> - Using Rosegarden 13.04
> - jackd 0.121.3 running SCHED_FIFO
> - alsa
> - Whatever linux kernel : 2.6.38 / 3.4.43 / 3.8.13
> - Whatever patchset : None / ck / CONFIG_PREEMPT_RT
> - All kernel configs with : CONFIG_SND_HRTIMER and
> CONFIG_SND_SEQ_HRTIMER_DEFAULT set.
>
> Everything audio / midi related works fine.
>
> HOWEVER
>
> As soon as I depress the apply button after changing the midi clock source
> from "auto" to "HR timer", my system entirely freezes and the hardware reset
> is the only solution left.
>
> What am I doing wrong ? What should I investigate ?
It's not Rosegarden's fault. It's simply a Bug in ALSA - the kernel
part, as far as I know. Unfortunately there's nothing what we can do to
fix it.
> BTW : What is the clock source actually used by Rosegarden when (auto) is
> selected ?
>
> Regards,
>
> aCOSwt
I don't know but you can prepare your Linux system best when you use a
"lowlatency" kernel. Some distributions offer one.
If the kernel version you prefer doesn't offer a lowlatency one you can
build your own.
- Get the source (preferably the same version of your running kernel)
- Unpack the source
- cd to the source
- cp /boot/config-<your kernel version> .config
- make oldconfig
- make menuconfig
Processor type and features
Preemption Model: Low-Latency Desktop
Timer Frequency: 1000 HZ
The rest depends on your distribution. Debian and Ubuntu create a
kernel- and a header-package with:
make-kpkg clean
fakeroot make-kpkg -j 4 --initrd --revision=1.0.hm kernel_image kernel_headers
(-j 4 is an acceleration for CPUs with 4 cores)
If you are a latency freak like me you can hear a slightly better
timing.
If your system offers Turboboost then switch it off in your BIOS. Else
the timing can be unstable. Speedstep can keep activated, it doesn't
harm.
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