Re: [LAU] midi keyboards, jackd, low latency

On Fri, Feb 27, 2009 at 1:11 PM, tizo <tizone@gmail.com> wrote:
> On Fri, Feb 27, 2009 at 12:36 AM,  <torbenh@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@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.

I meant "with -n2 is not possible".

>>
>> --
>> torben Hohn
>> http://galan.sourceforge.net -- The graphical Audio language
>> _______________________________________________
>> Linux-audio-user mailing list
>> Linux-audio-user@lists.linuxaudio.org
>> http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
>>
>
> Thanks very much,
>
> tizo
>
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Received on Fri Feb 27 20:15:06 2009