HOWTO: LOW LATENCY AUDIO the easy way

**mathieujohnson** · December 1st, 2005

Hi,
after a couple requests I have come to make this how to.
This is primarly for musicians, recording studios or basicly anyone who really cares about their audio performances under linux.

This how to is based on the great work of the Demudi/agnula distro.

first step to get a patched kernel for audio work is to add this line to your sources.list file :deb http://demudi.agnula.org/packages/demudi stable main

sudo gedit /etc/apt/sources.list
or sudo kwrite /etc/apt/sources.list

and copy past the line: deb http://demudi.agnula.org/packages/demudi stable main

then save the file
and
sudo apt-get update
sudo apt-get install kernel-image-2.6.12-3-multimedia-k7 (you can replace the last part with your appropriate architecture)
then when they ask if you want to stop now answer no
apt should resolve any dependencie problems, but in theory everything you need to make this kernel work is in the repo.
once this install is done, reboot and when grub menu appears choose the multimedia kernel and see wether jack can connect in realtime or not.
*****you can also update your version of jackd with that repository and a lot of other good stuff is on there*****

Thats it.

I got this working pretty good at 2.9ms latency without any problems.

my only concerns are to make amarok work with jack and basicly every app that uses audio to be routed to jack. still haven't got that going!

let me know if this is incorrect, doesn't work for you or if there are any mistakes.

and tell me how much you like it if it works.

**23meg** · December 2nd, 2005

With what audio device did you get the 2.9ms latency?

**mathieujohnson** · December 2nd, 2005

with the hammerfall dsp
RME multiface no problems at all and I don't have such a fast computer.
1.4ghz athlon XP 1600+
768mb ram DDR 266
40gb ata 100 7200rpm
160gb ata 100 7200rpm
matrox G450 16mb dual head (also have a Nvidia 64mb geforce 3 card but it only has one head, though I am trying it out as I was having display problems when too much eye candy was activated mainly with e17)

Haven't toyed with midi yet.
don't have any midi devices. mainly use virtual stuff like synths and drum machines and obviously plugin effects (I used to have a lot of outboard gear but I got rid of it, they didn't get any use)

**johannes** · December 2nd, 2005

Nice tutorial, thanks.

my only concerns are to make amarok work with jack and basicly every app that uses audio to be routed to jack. still haven't got that going!

I guess you have seen this Gentoo howto on Jack/ALSA stuff? I tried to do that in Ubuntu, but soon discovered that I would probably have to recompile ALSA, and I haven't got the time or patience to do that... If you get it to work, please write a tutorial!

Oh, I don't know if you already know this, but to be able to use Jack in realtime,

apt-get install realtime-lsm module-assistant
build the module with module-assistant
modprobe realtime gid=29

That should improve the audio in some cases.

**mathieujohnson** · December 3rd, 2005

I had already seen that how to for jack, though it is a good idea to post it in this thread so people have it in one simple place.
about the realtime-lsm module, there is a version in the demudi repo though I was never able to get it to work through module-assistant.
I beleive that it was allready loaded in the system if you used the demudi version AFAIK

**foxy123** · December 3rd, 2005

a stupid question: what is it for? I mean is it only for some professional needs or it will mprove sound quality in Ubuntu overall?

**23meg** · December 3rd, 2005

Originally Posted by foxy123

a stupid question: what is it for? I mean is it only for some professional needs or it will mprove sound quality in Ubuntu overall?

For audio production software only. It won't improve sound quality; it will only improve the responsiveness of the audio device to instructions.

**foxy123** · December 3rd, 2005

Originally Posted by 23meg

For audio production software only. It won't improve sound quality; it will only improve the responsiveness of the audio device to instructions.

oh, I see, thanks...

**mathieujohnson** · December 3rd, 2005

yeah basicly, if you don't have professionnal needs (or amateur, you know) well, this how to is not for you as this kernel is built for multimedia production hence is slower for other things like compiling (well, if you don't set the priority higher that is!)

**reet** · December 3rd, 2005

This sounds interesting, however with a different kernel I run into problems with my video drivers (Nvidia). I am told something about the Nvidia kernel module cannot be loaded because it hasn't been compiled for the new kernel. Am I going to have to abandon the .deb package for my video drivers and manually install them for this to work?

System Specs:
Athlon 2400+
768MB RAM
Geforce 6600GT
M-Audio Audiophile 2496