I am forwarding you my comments on this issue as I am not sure if you are getting them at this point because the bugs status still shows as rejected. this is in reference to the system timer resolution setting in the kernel.
>From the Rosegarden FAQ http://www.rosegardenmusic.com/resources/faq/#toc31 "5.6. What does "System timer resolution is too low" mean? If you see this message in an error dialog when Rosegarden starts up, then you are probably using a Linux kernel that doesn't offer sufficiently high-resolution system timers for MIDI use. Rosegarden uses ALSA sequencer queue scheduling (inside the Linux kernel) for its MIDI output. The sequencer queue can use a variety of timing sources, of which the default is the kernel system timer. The kernel system timer was 1000Hz in Linux 2.6 kernels up to 2.6.12, but as of 2.6.13 it's now 250Hz in mainline kernels. This is not good enough for good MIDI timing. Your options are: 1. Switch the sequencer to use a different timing source (Settings -> Configure Rosegarden... -> Sequencer -> Synchronisation). The best one in theory is the RTC timer, which is only available if you have snd-rtctimer loaded, but unfortunately that has a habit of totally locking systems running real-time kernels. Meanwhile, the PCM timers only work if the JACK audio server is running, and suffer jitter corresponding to the JACK buffer size. 2. Recompile your kernel with HZ set to 1000. Sadly there's no way to change this without a recompile. It's the best solution though. 3. Switch to a different Linux distribution that provides a kernel more appropriate for multimedia use. 4. Put up with the poorer timing of a 250Hz timer (if you want to get rid of the warning while continuing to use this timer, set the timer source to "system timer" rather than "(auto)"). Hopefully future versions of Rosegarden and/or the Linux kernel will provide better ways to solve this problem. " I tried using the RTC as the timing source as mentioned above and that causes the whole system to freeze. As I understand it their are plans to have a multimedia kernel ready for edgy. Perhaps this just needs to be part of that. I would also reccomend if using the Ingo Molnar's realtime patch on the new multimedia kernel to compile it with this option Preemptible Kernel (Low-Latency Desktop) - CONFIG_PREEMPT_DESKTOP and not Complete Preemption (Real-Time) - CONFIG_PREEMPT_RT The latter can cause some serious system instabilities. Some would probably disagree though because the latter provides super low latencies (as low as sub millisecond roundtrip) But that's probably another issue entirely. Re: Kernel timer resolution too low from Sheik Yerbouti at 2006-07-22 00:00:47 UTC As I learn more about this issue I am realizing the biggest thing affecting pro audio work on Ubuntu is the system timer resolution. Not only does it cause this error in Rosegarden it causes audio latency issues under jackd. With a stock Ubuntu 2.6.15 kernel with the system timer resolution changed to 1000 hz and a recompile my system will reliably do 128 frames buffer (5 msecs latencies) with 0 buffer over runs or under runs in jackd. Whereas with the current stock kernel at 250 hz system timer I would get under runs and over runs all the way up to 22 msecs latencies. This is starting to look like a big issue to me. I personally spent a month tweaking my Ubuntu system for audio work. And now it appears to me this one kernel setting was the real culprit. Right now a noob to Ubuntu pro audio is directed to recompile the kernel straight off. This is not really ideal at all. At the very least couldn't there be an 1000 hz timer kernel option in the repositories? Then at the ubuntustudio.com wiki we could point new users to try this kernel first before recompiling from scratch and going full RT with Ingo's patch? Cheers, Allen On Wed, 19 Jul 2006 16:58:35 -0000, "Ben Collins" <[EMAIL PROTECTED]> said: > 1000HZ is way to high for a lot of systems. Particularly laptops, where > the high timer resolution causes uneeded battery drain. > > How does MIDI require 1000HZ? MIDI has been working in Linux a long > time, likely predating the time where the kernel worked with anything > except 100HZ. > > ** Changed in: linux-source-2.6.17 (Ubuntu) > Status: Unconfirmed => Rejected > > -- > Kernel timer resolution too low > https://launchpad.net/bugs/53365 -- Allen Jeter [EMAIL PROTECTED] -- Kernel timer resolution too low https://launchpad.net/bugs/53365 -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
