Hello. I am trying to successfully configure my Lexicon Omega USB interface to use with Ardour. Here’s some info about my system:
Ubuntu 10.10 Maverick Meerkat
AMD Athlon 64x2
2.6.33-29-realtime kernel from Alessio Igor Bogani (https://launchpad.net/~abogani/+archive/ppa/+packages)
2GB Ram
Ardour 2.8.11 (built from 7387)
jackdmp 1.9.6
I am using 256 Frames/Period and 3 Periods/Buffer at 48kHz sample rate.
This works fine for recording one track, but I’ve been having problems figuring out input latency in order to successfully sync overdubs.
Using jdelay gets me 1498.727 (give or take a few thousandths) immediately after server initialization. If I switch tasks however (open a web page, change windows, etc), I get an XRUN and the jdelay output changes. Here’s an example (in order to make it shorter I cut out long periods of repetition).
1498.727
1498.726
1498.727
1498.727
1498.728
1498.727
1498.727
1498.727
1498.727
1498.727
1498.727
1498.727
1498.726
16290.728 ?? Inv
16290.728 ??
52146.728 ?? Inv
1402.727
1402.727
1402.727
1402.728
1402.728
1402.728
1402.726
1402.727
etc…
…1402.727
1402.727
1402.727
1402.727
50994.726 ?? Inv
1258.728 ??
1258.727
1258.728
1258.727
1258.727
1258.726
etc…
…1258.727
1258.727
1258.728 ??
52930.727 ?? Inv
1162.728 ??
1162.727
1162.727
1162.727
1162.728
etc etc
I have currently input latency set to 1242 (1498 from jdelay minus 256 frames/period). But this evidently is not reliable, since it appears that the total latency varies.
In Ardour I notice this because when I overdub rhythmic music, the tracks are always out of sync. I’ve also tried recording the click through an analog patch cable from the monitor back to the input of my interface. The resulting audio track doesn’t line up with the click it’s sourced from (when I play back the recorded click track with the Ardour-supplied click activated, you can hear a distinctive flam). Any ideas?