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List:       freebsd-multimedia
Subject:    Re: jackd
From:       Ralf Mardorf <ralf.mardorf () alice-dsl ! net>
Date:       2013-05-18 9:42:29
Message-ID: 1368870149.671.83.camel () archlinux
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On Sat, 2013-05-18 at 17:02 +1000, Ian Smith wrote:
> Re what Diane said, that seems also to be the case on linux

Hi :)

I reply from my "pro-audio" (bizarre term) Linux DAW ;). Are you talking
about real-time for the users?

On Linux even a vanilla kernel can be used with real-time abilities +
you can configure it to _full_ preemption and enable threadirqs when
booting, without patching the kernel. Im using a real-time patch for my
kernels, but the difference to a full preempted kernel are minimal.

Usually real-time permissions are given to the user by PAM,
http://www.jackaudio.org/linux_rt_config .

FWIW if on FreeBSD real-time is an issue, there still is the possibility
to take care about some other stuff, that could harm audio performance.

On my machine I unbind some USB ports, that share the IRQ with one of my
sound cards.

echo -n "0000:00:13.2" > /sys/bus/pci/drivers/ohci_hcd/unbind
echo -n "0000:00:13.4" > /sys/bus/pci/drivers/ohci_hcd/unbind

There isn't a difference for the performance on my machine, but perhaps
this can help on other machines.

You can stop services, bluetooth, cups, resp. remove drivers for
firewire, parallel port, printer.

http://wiki.linuxmusicians.com/doku.php?id=system_configuration

It's said that editing PCI bus latency isn't a good idea and IIRC it has
got no impact to PCIe, but I might be mistaken.

http://www.mythtv.org/wiki/PCI_Latency

Using Linux for pro-audio (this term simply is for "good working audio",
not only for professional usage ;) IMO still is luck of the draw, but
possible and this by running jackd as user.

Regards,
Ralf 


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