Jackd distortion or Jackmp xruns...

  • Patrice Brousseau
Posted: Sat, 02/09/2008 - 12:50
Hello, I'm a long time Sonar user in WinXP and would like my 64Studio partition to perform the same as it works on the WinXP side. To make a short story: I can go as low as 64 samples with my Echo Mia (ASIO driver) without dropouts (it's the Windows word for xruns) and this, under heavy cpu load and big streaming samples plus a reverb... Strangely, I'm not able to set jackd at 64 frames without obtaining a kind of "buzz" (distortion) under a similar load in 64Studio. More strange, there's no xruns reported by Qjackctl, just that distortion that suddenly appears. Closing the applications and restarting Jack (jack103) cure the problem temporarily until it happens again... Please note that going to bigger frame (128), the situation is the same. As a workaround, I installed jackmp in place of the regular jack but now, instead of distortion, I get xruns at 64 frames. Not a lot but enough to find it annoying! If I set jackmp at 128 frames, I have practically no xruns. So far, I tried to play with latency settings (setpci), I replaced the xorg Matrox drivers with another one (a little success because I have less xruns), I installed the package RTIRQ (stranglely it increases the number of xruns so I finally removed it). I also tried different kernels (2.6.21, 2.6.22, 2.6.23, 2.6.24) and even compiled myself different versions. On the jack side, I compiled several versions of jack or jackmp without obtaining the same performance I get under XP, i.e., no xruns with jackmp or no distortion with jackd. Maybe I overlooked something or there's something wrong with my hardware under Linux? **I just tried to replace the Alsa package with 1.0.16 but no improvement either... My specs: AMD Athlon 3800+ dual-core 64Studio 32-bit (because I want to use VST's) Gigabyte K8U-939 (Uli chipset) Echo Mia first generation on its own IRQ (22) 3 hard disks: one IDE for the OS'ses, one IDE for Audio data and one SATA for my samples (soundfonts, gigs,...) Matrox AGP G450 dual-head runing with unofficial Linux drivers in MergeFDB mode *All services to the bare minimum **Please note that I also tried the JAD distro and it exhibits the same behavior. Any useful advice will be welcomed. Thanks and sorry for the long post.
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Well thanks for the very old

  • jaywilson
  • 06/02/07
  • Thu, 05/28/2009 - 21:45
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Well thanks for the very old tip, I just reloaded a .rg arrangement using Zyn and got the same buzzing distortion although it worked fine yesterday. In my JACK messages I read the following. subgraph starting at qjackctl-5772 timed out (subgraph_wait_fd=17, status = 0, state = Finished Didn't know what that meant but setting Frames/ Period to 32 and Periods/ Buffer to 7 fixed it. "A father is someone who keeps photographs where his money used to be."

number of buffers

  • ttoine
  • 11/15/07
  • Wed, 02/13/2008 - 17:42
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Hey, I have several sound cards : RME, Presonus, Echo, plus the motherboard soundcards of my pcs. What is amazing with the number of buffers, is that some cards will not run at all if you don't put the right number, and other will work with distortion. My RME hdsp and my Echo IndigoI/O will run best at 2, the Presonus Firebox only at 3 (or won't start), and for the motherboard soundcards of the workstation and the laptop, 2 or 3 depending on Intel soundchipset. I teach audio on Linux with Ardour2 at the Lyon II faculty, and depending of the soundcard, there is always a bit of testing before jack will start well. So my first topic is always about jack configuration. I really start teaching Ardour2 when jack run well on all people workstation or laptop. Most of the time, 2 and 3 are the good values, for what I see. Toine ps : It is amazing to see that you can run your Echo soundcard on Windows at a so very small latency. You should have a very good workstation.

(kind of) SOLVED

  • Patrice Brousseau
  • 06/04/07
  • Sat, 02/09/2008 - 15:58
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Hi, It's a weird one: I found the solution by accident. I changed some values in the BIOS and went to QJackctl to reset the frame size to 64 but instead (without) noticing, I set it to 32. Then, my habitual test with a couple of applications and... no distortion with Jackd. Good, I was going to look at which setting in BIOS made things ok when I discovered that the frame size was at 32. So, I let it at 32 and increased the number of buffers to 4 (thus having 2.9ms reported by Qjackctl as before) and... no distortion too. For now, as a workaround, I have to let the frame size at 32 and change the number of buffers to increase or decrease the latency. I do not fully understand why but it works... Maybe something with the internal functionning of the Echo Mia!