[ardour-dev] Strange Issue WIth Automation in ardour-0.9_beta11

[David R. Bergstein]

I recently ran into some problems whenever automation is enabled on any 
track with ardour-0.9_beta11. These were usually indicated as disktream 
errors in the ardour log window, and when checking the log generated 
from jackd and ardour (this is run as an sudo session on a script in my 
home directory), there were playback underruns shown that seemed to 
correlate with the log window errors.  A sample of these errors is 
copied below:

---------------------------------------------------------------------
DiskStream Vocals:0: playback underrun (called with 8193 samples but 
only 5933 vailable; other half: 0) [speed=8]
---------------------------------------------------------------------

My system is an Abit BX6-R2 with a Pentuum III 450 (Katmai), 768 MB RAM, 
Hammerfall DSP 9652, using reiserfs as the filestore for my audio files, 
and jack-audio-connection-kit-0.94.0 compiled /dev/shm on tmpfs.

Another, possibly unrelated, dilemma is an issue I have been 
encountering when running latencies (with or without automation) at or 
below 3 ms latency (i.e., p=256, n=2 @ 48KHz sampling rate) when running 
a 2.4 kernel. In this case, the ardour log window displays a bizarre 
error message saying something about a MIDI memory pool error and to 
please compile with larger size.  When I run a 2.6 kernel, this error 
does not seem to occur.  FYI, this is on a gentoo linux installation, 
tested with the following kernel versions and settings:

ck-sources-2.4.23-r1 wirh lowlatency and preempt enabled
gentoo-dev-sources-2.6.3-r1 with elevator=as and preempt enabled

Please note that I have already optimized my IRQs and hdparm settings 
based on the FAQs I read for linux audio, and to reduce the possibility 
PCI bus contention I am running an Nvidia AGP card with the open source 
(nv) driver in XFree86 (build from gentoo ebuild xfree-4.3.0-r5).  While 
investigating this issue, I have also set my startup script for jack 
ardour to shutdown local services that might be in contention, and I 
have set all of my reiserfs filesystems in /etc/fstab to run with the 
notail,noatime parameters (noatime was added during my diagnostic 
sessions), however, the disk stream errors persist whenever automation 
is enabled and my system latency is set any lower than 11ms 
(p=1024,n=2 at 48KHz).

My current workaround is to run the gentoo development kernel 2.6.3-r1, 
and use low latencies as low as 3 ms for recording or non-automated 
mixdowns, and a setting of 11ms latency or greater if I am mixing down 
with automnation.

Can anyone suggest a more elegant solution or is there a fix in the 
works to make automation in ardour less resource intensive?

Regards,

- David

-- 
David R. Bergstein
Systems Engineer and Blues Musician
http://home.comcast.net/~dbergstein
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