3 Dec
2016
3 Dec
'16
8:50 p.m.
On Saturday, December 3, 2016 1:20:09 PM EST David Klann wrote:
Greetings,
Long-time Linux user, and relatively new JACK user here. I have built
some audio workstations for the community radio station where I
volunteer (WDRT, Viroqua, WI, US). I recently switched one of the
workstations to use JACK, along with PulseAudio. We use Audacity to edit
audio and we have noticed that the "left" and "right" channels are
out
of sync with each other. We have witnessed the "skew" to be as few as
two samples (which is unnoticeable to the ear) to as many as a couple
hundred samples (which sounds a lot like a phase error).
We performed a lot of troubleshooting, including swapping PCI audio
cards (ESI Juli@, Digigram VX222), disabling JACK, running Audacity on
the same hardware booted from a USB stick and a completely different
Debian environment. I am not *completely* confident, but the likely
culprit seems to be JACK.
We have recorded audio using jack-record and experienced the same
left-right channel skew.
Can anyone help point to JACK or OS configuration parameters that we
might look at to get our left and right channels in sync?
Details:
OS: Debian Jessie (8.6), up to date (kernel: 3.16.0-4-amd64 #1 SMP
Debian 3.16.36-1+deb8u2 (2016-10-19) x86_64 GNU/Linux)
JACK (jackd2): 1.9.10+20140719git3eb0ae6a~df
PulseAudio: 5.0-13
ALSA: 1.0.27+1
CPU: Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz
RAM: 8GB
Audio Cards: ESI Juli@ PCI, Digigram VX222HR PCI
Thanks for your consideration!
~David Klann
Hello, this might be a long shot, but maybe not.
You mentioned it did this when Jack was disabled,
so it seems Jack is not the problem.
Look for the LAU thread on Wednesday titled:
"[LAU] [SOLVED] Crackles in audio, drifting intermittent noise etc."
I was having very strange phasing problems, although I didn't notice
from channel to channel but I wasn't really listening for that.
I knew it was hardware related, only that could cause it.
My ONLY solution was changing the number of enabled CPU cores,
either through my BIOS or through Linux commands such as:
echo 0| sudo tee /sys/devices/system/cpu/cpu3/online
cat /sys/devices/system/cpu/cpu3/online
I found that I must run with just ONE core for the most stability.
(I had posted that I found TWO cores were OK but actually
further test revealed it was not OK.)
So try:
echo 0| sudo tee /sys/devices/system/cpu/cpu1/online
echo 0| sudo tee /sys/devices/system/cpu/cpu2/online
echo 0| sudo tee /sys/devices/system/cpu/cpu3/online
cpu0 will always be online.
Tim.