[ardour-users] Xruns, and buffer sizes... Continued recording problems.

[Jason Jones]

>You didn't mention this in your initial mail: Do you run jackd with 
>realtime capabilities? Is your kernel patched for low latency? If not 
>forget *all* of your xrun symptoms and try that.
>
>  
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Yes.  I'm running qjackctl with realtime capabilities.  As far as the 
patched kernel, I'm using gentoo with the 2.6.8.1-mm4 kernel (multimedia 
kernel) which supposedly has Andrew Morton's patches applied to it.  
I've heard conflicting stories from various websites about the 
superiority of 2.6 or 2.4 kernels.  Almost all of the documentation I've 
read about low latency is out-dated, so I don't know what to believe.  
If installing a 2.4 kernel will get me better performance, I'll *GLADLY* 
do it.  At this point, my band is beginning to doubt the feasibility of 
using Ardour to record our albums...  I'm slightly frustrated by these 
xruns, but I know it's due to nothing more than my own inexperience and 
ignorance about latency in Linux.  We'll get it running sooner or later.

>>changed my periods to 2048, and my recording rate to 44.1K - (I tried
>>setting it to 4096, but when I tried to start jack, it told me alsa
>>wouldn't allow a period with that setting...  Is that normal?)  I had
>>    
>>
>
>Alsa drivers reflect -- in the best case -- the hardware's limitations 
>including buffersize limits.
>  
>
Good to know.  Is the -p setting the "buffer"?  or is it the combination 
of the recording frequency, the frames, and the periods?

>  
>
>>The only thing I can think of to get rid of the xruns is to start
>>removing hardware (like my wireless NIC... maybe my second video
>>card, although that one would hurt.  I use the full screen of both
>>screens...
>>    
>>
>
>Before doing that it would make sense to google for "pci latency" and 
>read http://myweb.cableone.net/eviltwin69/ALSA_JACK_ARDOUR.html
>  
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I'll start that right now.  I'll get back with what I find.

>  
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>>:-(  )...  Maybe start removing processes which are running...  I've
>>    
>>
>
>The recent discussion of lighweight windowmanagers was misleading. If 
>you run jackd with realtime capabilities on a low lat kernel you can 
>run KDE, watch flashs and abuse openoffice while ardour is happily 
>playing out 20 tracks. Things might be sluggish but there will be no 
>xruns.
>
>  
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Great info.    Would you mind describing to me exactly what an "xrun" 
is?  What are it's causes?  Maybe a fact vs. myth thread?

>btw: Could you try to start new threads for new questions?
>
>  
>
Absolutely.  I apologize for not doing so last time.

Some things I've considered doing to get rid of the xruns, but I have no 
idea if they're going to be effective:

1. Using a ps/2 mouse instead of a USB one, and turning off USB 
capabilities.
2. Taking out my wireless NIC (not using it anyway).
3. Using xterm to start my qjackctl program instead of gnome-terminal 
(although I have it minimized while recording)
4. Using "jackd -R -d alsa...." instead of qjackctl in xterm.
5. Disabling hardware accelleration for my NVidia cards by using "nv" 
instead of "nvidia" (found that one through google last night).  Maybe 
just turning off the GLX drivers would suffice?  (Not using DRI, either).
6. Disabling everything I'm not using in my kernel (IEEE1394, USB, 
Networking, etc...).

Would those things help me?  Or would it be irrelevant?

Thanks again for your help.

--Jason