[LAU] Intel-hda jack low latency howto

A intel-hda jack low latency howto (by wirelessdreamer)

I've seen asked many times on the list how to get intel-hda cards working
with low latency, in duplex operation. Here is a full, step by step, on how
I got 4ms latency. I'm using a Dell M90 with a Quadro fx 1500, attached to a
docking station with a Maudio Delta 66 pci card (secondary card) in it, the
binary Nvidia drivers and Compiz. So if you were wondering, it is possible.
:)

1. Kernel (i'm not going to walk you through how to compile a kernel)

(the last kernel before the big kernel lock regression)
* wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.24.7.tar.bz2

* tar xvjf linux-2.6.24.7.tar.bz2
* cd linux-2.6.24.7.tar.bz2

(if you don't see it here look in the projects/rt/older/ directory)
* wget
http://www.kernel.org/pub/linux/kernel/projects/rt/patch-2.6.24.7-rt21.bz2

* bzcat ../patch-2.6.24.7-rt21.bz2

* wget http://pastebin.com/pastebin.php?dl=f6ad31838
* mv pastebin.php\?dl\=f6ad31838 .config.old
* make oldconfig

(build and install your kernel)

2. Module Options
Add the following line to the file your distribution has its module options
in
(in ubuntu it is /etc/modules.d/alsa-base)

options snd-hda-intel model=ref position_fix=1 enable=1 index=0

3. Mixer Options (VERY IMPORTANT ! ! !)
enable capture/record elements in mixer
without this jack can't play nicely with intel-hda cards

4. RT Permissions
In most modern distros /etc/security/limits.conf is where realtime
permissions are set, I added these 3 lines to it, and added myself to the
@audio group in /etc/group

@audio - memlock 1024000
@audio - nice -10
@audio - rtprio 99

5. Jack options
I use qjackctl to set these

put a check in Realtime
Priority 89
Frames/Period 64
Sample Rate 48000
Periods/Buffer 3

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Received on Sun Nov 2 20:15:02 2008