Tutorial: Realtime (RT) Audio on Linux: The Basics (for Laymen)

This video provides a simplified explanation of what RT audio is, what its purpose is, and how to set it up on newer (2.6.xx) linux kernels.

Please note that the explanations in this video are gross oversimplifications and are intended for the technically savvy, but not for linux experts!

The information currently floating around both youtube and the web in general is generally VERY outdated and far, far more complicated to use than it should be. Realtime audio is a snap to set up and requires absolutely minimal coding/programming knowledge or linux knowledge.

Here's a really interesting document on the history of realtime audio in linux and the patched 2.4 kernel:

http://lac.zkm.de/2006/papers/lac2006_lee_revell.pdf

NOTE: There are NUMEROUS additional steps one can take to completely optimize a system for realtime audio, but this is the most basic, most simple step towards enabling it.

Don't forget to watch in 720p HD.

Category:

Science & Technology

Tags:

• linux
• realtime
• RT
• audio
• tutorial
• kernel
• unix
• distro
• ubuntu
• real
• time
• music
• production

[jaaxxone]

Not sure about setting your limits at the user level. Would be better to use the @audio group so only those processes get the increased privs. Otherwise, any old user process (gnome panel, notifications, browsers, etc) can steal resources during the middle of your recording sessions!

[jkymarsh]

@jaaxxone This is untrue. First off, placing users within in Audio group doesn't have anything to do with determining what programs use RT priorities; it's simply a naming system used to keep things straight if a lot of users use your system. Programs don't know (or care) what user group you're a member of. Secondly, programs don't inherently use unbounded amounts of system resources; they have to specifically be configured to do so.

[Ejacka]

Changed file permissions:

sudo chmod limits.conf -rwxrwxrwx

but got this message:

"Could not save the file /etc/security/limits.conf.

You are trying to save the file on a read-only disk. Please check that you typed the location correctly and try again."

[jkymarsh]

@Ejacka Try actually logging in as root rather than using sudo. If that doesn't work, you may want to alter your chmod tactic... Using chmod ugo=rwx (or some variation thereof) has always been more reliable and straightforward for me. (Also, doesn't a hyphen before the permissions arguments remove from a file/directory?)

[fatsterfatster]

INteresting, but one thing I don't understand is what's the difference between soft and hard limits and the "-" ?

[jkymarsh]

@fatsterfatster A soft limit is a default value when a user logs in, and this value can be increased using the terminal "ulimit" command. However, we're not interested in either a soft limit or a hard maximum limit, nor using "ulimit" to manually change anything, so we don't have to bother with hard or soft at all.

[belevtsoff]

I'm afraid all it does is just allows a non-root user to renice processes. In order to get hard real-time perfomance one needs to run patched kernel. I tried doing things adviced in this video but got no perfomance increase (comared to same thing ran with root). After patching a kernel I can run JACK with under 1ms latency with no Xrun's. Cheers

[wtilkin]

This video is a nice tutorial to optimize the standard linux for realtime audio, but it's still using soft real-time kernel, which has nothing to do with hard real time does it?

[Komputerism]

I can run my nord rack2 with hydrogen drum machine cortoled by seq24 now. thank you.

[Wintershade3001]

@1:48 Finally! Somebody making a sane statement about linux-rt kernel. Thank you, friend.

[Don70rEnZ0]

Great way of explaining and teaching us, thank you for your kind work,

[icemanguitar]

tahnk you thank you =) =)

[aynrandy1]

I'm in MEPIS, so I had to log into the actual root login to make these changes.

I couldn't save the changes from my user account with root privileges.

But it worked fine after changing it in the actual root account of MEPIS.