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Thread: Jackd Latencies through roof in Hardy

  1. #1
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    Jackd Latencies through roof in Hardy

    I have been trying since upgrading to Hardy to get Jackd and Ardour setup for recording. Ever since clean installing hardy and setting up the realtime kernel I haven't been able to get back to where I was when I ran Gutsy with the same sound hardware. I have a Behringer U-Control UCA-202 on the way and we'll see. The only thing I have not done was compile my own kernel to see if I can solve this issue. I use the following to start jackd:

    /usr/bin/jackd -v -R -P89 -p128 -t5000 -dalsa -dhw:1 -r44100 -p2048 -n5 -D -Phw:1,0 -i2 -o2

    This is with a Griffin iMic Currently. Am I EVER going to get back to 10 ms latencies (which isn't great, but MUCH better than this) and no xruns?? Possibly? Anyone got ANY idea??

    Saw the following on the ALSA Wiki:

    Tuning USB devices for minimal latencies

    On linux-audio-user Christoph Eckert brought up the question about how to get better latencies out of USB audio devices, and USB guru Clemens Ladisch had a very good tip: The snd-usb-audio module accepts a module option called "nrpacks", which according to modinfo, sets the: Max. number of packets per URB. (int). Setting this to "nrpacks=1" should allow latencies in the area of 4-6 msecs.

    Unfortunatly on some systems/kernels nrpacks=1 conflicts with a feature called "USB bandwidth allocation" in the kernel. Here's the way out:

    * In the kernel config ensure that both options (taken from a 2.6.10) are disabled::

    :[ ] Enforce USB bandwidth allocation (EXPERIMENTAL)
    :[ ] Dynamic USB minor allocation (EXPERIMENTAL)

    * Ensure to loTuning USB devices for minimal latencies

    On linux-audio-user Christoph Eckert brought up the question about how to get better latencies out of USB audio devices, and USB guru Clemens Ladisch had a very good tip: The snd-usb-audio module accepts a module option called "nrpacks", which according to modinfo, sets the: Max. number of packets per URB. (int). Setting this to "nrpacks=1" should allow latencies in the area of 4-6 msecs.

    Unfortunatly on some systems/kernels nrpacks=1 conflicts with a feature called "USB bandwidth allocation" in the kernel. Here's the way out:

    * In the kernel config ensure that both options (taken from a 2.6.10) are disabled::

    :[ ] Enforce USB bandwidth allocation (EXPERIMENTAL)
    :[ ] Dynamic USB minor allocation (EXPERIMENTAL)

    * Ensure to load the snd-usb-audio module with the parameter "nrpacks=1", maybe including it into one of the boot scripts::

    modprobe snd-usb-audio nrpacks=1

    * Or use the module configuration line (e.g. in /etc/modprobe.conf):

    options snd-usb-audio nrpacks=1

    * Now invoke JACK with the following command (or entering the corresponding values into Qjackctl):

    jackd -R -P89 -dalsa -dhw:2 -r48000 -p256 -n3 -S

    You can omit the "-S" if your card supports 24bit or 32bit access as well and you want to use that.

    Request: could somebody please provide info on what needs to be done to set IRQs properly? ad the snd-usb-audio module with the parameter "nrpacks=1", maybe including it into one of the boot scripts::

    modprobe snd-usb-audio nrpacks=1

    * Or use the module configuration line (e.g. in /etc/modprobe.conf):

    options snd-usb-audio nrpacks=1

    * Now invoke JACK with the following command (or entering the corresponding values into Qjackctl):

    jackd -R -P89 -dalsa -dhw:2 -r48000 -p256 -n3 -S

    You can omit the "-S" if your card supports 24bit or 32bit access as well and you want to use that.

    Request: could somebody please provide info on what needs to be done to set IRQs properly?

    Are these options disabled in the default realtime kernel on Hardy?? Seems kind of stupid to have Experimental options on in a LTS.

  2. #2
    Join Date
    Jul 2005
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    Re: Jackd Latencies through roof in Hardy

    More investigation. I found that no matter what I did in /etc/security/limits.conf I was unable to get the nice level up of jackd. At least that's what I thought happened unless System Monitor is lying to me!

    Pulse Audio is running at -11 nice level.

    Also, I noticed the standard audio group seems to be missing in Hardy. I try adding it by hand and was unable to add it. I assign rtprio to my own signon in /etc/security/limits.conf as well as the memlock and other line.

    Right now, I am about ready to revert back to gutsy and just deal with some of the issues I had on gutsy that I don't have in Hardy (namely, suspend doesn't work on Gutsy on my Lenovo T60).

    I have a hunch that Pulse is the culprit here possibly. Things have just NOT worked as well on Hardy for audio production as it did on Gutsy.

  3. #3
    Join Date
    Apr 2006
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    Re: Jackd Latencies through roof in Hardy

    Seems like linux-rt in hardy has serious troubles keeping low latencies.
    Running cyclictest from rt.wiki.kernel.org gives latencies up to 1800 us in my system.
    Don't know how to fix it. I tried to compile the latest rt patch (2.6.24.4) in a vanilla kernel but it doesn't get any better.
    I'm rolling back to gutsy by now.
    Maybe when the rt patch comes out for 2.6.25...

    If anyone has a solution, please share!

    Regards

  4. #4
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    Re: Jackd Latencies through roof in Hardy

    Quote Originally Posted by friderman View Post
    Seems like linux-rt in hardy has serious troubles keeping low latencies.
    So it's NOT JUST ME??? WOO!

    I am looking at downloading JackLab or something else until I see something different.

    It's a shame because the rest of Hardy is friggin outstanding!

  5. #5
    Join Date
    Nov 2006
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    Re: Jackd Latencies through roof in Hardy

    go 64studio, it's debian under, the father of ubuntu so it won't be too foreign (jacklab is suse, the admin is sorta different than on debian systems)

  6. #6
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    Apr 2006
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    Re: Jackd Latencies through roof in Hardy

    Quote Originally Posted by gorkon View Post
    So it's NOT JUST ME??? WOO!

    I am looking at downloading JackLab or something else until I see something different.

    It's a shame because the rest of Hardy is friggin outstanding!
    It's not just you... It's not pulseaudio either - I've tried out my usual workflow after 'killall pulseaudio' and realtime performance is still appalling. I've gained some improvements by stopping compiz in favour of metacity, but even so, my UCA202 (the device you're buying) is running at some 69ms latency (opposed to the 11ms or lower I used to get)'

    If compiz is interfering with realtime performance, that's going to be really irritating. After all, OSX has a composited, 3D accelerated GUI and a low-latency audio server...

    Ah well, bug report time...

  7. #7
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    Apr 2006
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    99

    Re: Jackd Latencies through roof in Hardy

    I've reported a bug. Please add as much detail as possible, guys.

  8. #8
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    Re: Jackd Latencies through roof in Hardy

    Quote Originally Posted by prismatic7 View Post
    I've reported a bug. Please add as much detail as possible, guys.
    Thanks for doing the bug report. I concur...still have the issue with my Behringer too.

    At the rate I am going, Gutsy may be going back on this machine. I have a old athlon box with Gutsy on it now, but the fan in it is so damn noisy recording on it would SUCK!

  9. #9
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    Re: Jackd Latencies through roof in Hardy

    Quote Originally Posted by prismatic7 View Post
    I've reported a bug. Please add as much detail as possible, guys.
    I read your bug report and I don't think it has anything to do with compiz, perse. I think it's a kernel issue. specifically, those 2 experimental USB items I posted earlier in the thread.

    Either that or something in the configuration is munged between gutsy and hardy.

    Incidentally, I also tried this on Ubuntu Studio and while having less configuration to do (it seems the linux-rt package should setup the security limits....it doesn't), it still is xrunning like crazy even after disabling Compiz.

  10. #10
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    Jan 2005
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    Re: Jackd Latencies through roof in Hardy

    Are running actual Studio or Ubuntu with -rt kernel?

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