[LAU] midi keyboards, jackd, low latency

tizo tizone at gmail.com
Fri Feb 27 10:11:45 EST 2009

On Fri, Feb 27, 2009 at 12:36 AM,  <torbenh at gmx.de> wrote:
> On Thu, Feb 26, 2009 at 06:21:48PM -0500, Paul Davis wrote:
>> On Thu, Feb 26, 2009 at 4:20 PM, tizo <tizone at gmail.com> wrote:
>> > Hi there,
>> >
>> > Sorry about my previous mail. I was just starting to write a draft
>> > about the topics I want to ask, and I accidentally push the send
>> > button.
>> >
>> > Well, my goal is to play two midi keyboards, sending the events
>> > through jackd, to qsynth. My computer is a Laptop HP 550, with HDA
>> > Intel sound card, 3 GB of memory, and a Core 2 DUO CPU of 1.40 GHz. My
>> > OS is UbuntuStudio 8.04, with kernel 2.6.24-23-rt.
>> >
>> > First of all, I cannot run jackd without xruns, if I configure it with
>> > 32 frames per period, or less. I am running it as root, with realtime,
>> > and a priority of 70. As soon as I run it, it starts to count xruns,
>> > and I am only executing jackd.
>> 32 frames per interrupt is VERY ambitious with an Intel HDA chipset. Its not
>> impossible but every single part of your system has to be "just right" for
>> this to work. I would start with a less ambitious goal first, and get some
>> experience with the setup before trying to get all the way to this latency
>> level.
>> moving to USB will likely make things worse. latencies like this are best
>> accomplished with good, prosumer level PCI audio interfaces.
> and most certainly not with a kernel that old.
> the old hda drivers are totally broken.
> a quick test on vanilla 2.6.28 shows it runs at -p32 -n3.
> but it gives me some xruns when i switch desktop.
> -n2 is not possible. i get xrun streams.

I have tried UbuntuStudio 8.10; I can't remember nor the version of
the kernel, neither the jack performance, but that kernel had a
reported bug, that broke the usb connections with midi keyboards.

Maybe I will try another distribution and/or kernel, but that bug has
to be fixed for me to be useful.

I am running jackd with -n3 too; as you said, with -n3 is not possible.

> --
> torben Hohn
> http://galan.sourceforge.net -- The graphical Audio language
> _______________________________________________
> Linux-audio-user mailing list
> Linux-audio-user at lists.linuxaudio.org
> http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user

Thanks very much,


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