[Ardour-Users] My Recent Struggles With the RT kernel and Ardour - With Happy Ending

JOHN LYON jalyon at shaw.ca
Tue Dec 23 08:21:23 PST 2008

I'd like to share my recent experiences with the Linux rt kernel, Ardour and jack. 

The short version: my problem was the XFF nForce 680i LT SLI motherbaord. When I fianlly swapped in an Asus P5QL Pro motherbaord, I could use the Linux rt kernel at very low latencies without any xruns.

The Longer Version:

My goal this past fall was to use Linux and Ardour to record a CD (I'm a jazz singer and 7-string guitarist).  The idea was to produce some music with very high production values (as I high I could get them given that I'm relatively inexperienced as a recording engineer) but without having to spend much money (I'd like to add that I have contributed to the Ardour fund, and will continue to do so).  I did spend a lot of time and effort learning about and implementing some nice acoustic room treatments (homemade bass traps and quadratic residue diffusors seemed the best bang for the buck).  I also have an M-Audio Delta 1010LT 10-in, 10-out sound card, which I think is also great bang for the buck.  I also own some nice mic preamps, including the FMR RNP "Real Nice Preamp". And I'm currently renting an ART TubeFire 8-in, 8-out mic preamp system with firewire (I can't seem to get the firewire part working under Linux, but it's not supported in freebob or ffado, so I'm not surprised about that).  

I have friends in the business of commercial audio recording and one of them tells me I need to forget about Linux and switch over to the Mac with (say) Apogee firewire A/D D/A converters. Fortunately, I recently met another respected audio professional here in the greater Vancouver area who loves Linux (he uses both the Mac and Linux), and is very impressed with Ardour.  (Wow, is it ever cool to run into another fellow traveller).  

The next piece of the puzzle would be to really learn how to use ardour and qjackctl, and eventually attempt the mastering with Jamin.  

I spent over 3 weeks trying to get them working with the rt kernel. I tried every kernel I could get my hands on.  No luck. Non-pre-emptive kernels worked great, but with very high latencies -- I ended up using up to 7 buffers in jack and I could never get below about 256 or 512 without running into LOTS of xruns.  I was using a pentium D chip in an XFX 'gaming' motherboard I got for cheap from tigerdirect.ca.  

I tried running CentOS. No joy. I tried swapping out the pentium D for a pentium core 2 duo. No joy. (Man, I got so sick of rebooting and waiting for the system to come back up). 

I finally got the bright idea of swapping my XFX motherboard with an ASUS P5QL Pro. At first it wouldn't even boot (this is a known bug --- a few versions of the kernel -- between 2.6.25 and (where it was supposedly fixed) would not boot when using the Asus P5QL Pro motherboard).  

But there is a lovely happy ending to this story. I'm using this kernel on Fedora Core 8:  Everything works!    I've been reluctant to experiment with never rt kernels because "it ain't broke". Here is my jack command line setting:

 /usr/bin/jackd -R -P80 -dalsa -r48000 -p128 -n3 -D -Chw:0 -Phw:0

I have not seen a single xrun. I'm only using jack and Ardour (and the gverb plugin) so far, but it's been running for over a week, with several songs recorded, and no problem whatsoever.

I can't tell you how stressful the previous several weeks were. You see, I've been using Linux since 1994, with nothing but satisfactory results.  I had come to trust Linux, as the OS that would always carry me through, whether as a web server, an SQL database, email server, environment for learning programming languages, what have you. I've been a Linux fan and evangelist for all those years, and Linux never let me down before.  I know the rt kernel is the weak link in the chain at present, and I understood that it simply wouldn't work on some hardware.  But I had never actually run into that problem until now.

So now I'm back on track, reading the Ardour manual, looking for howtos and tutorials, trying to find examples of music recorded using this software, and so on.  Whew!  This is where I wanted to be a month ago!

I hope this proves useful to some of you who may be going through similar struggles with the rt kernel. 

Cheers and the Best Of The Season,

John Lyon
North Vancouver
British Columbia

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