Re: [LAU] "Skewed" Audio with JACK

There's more or less no way for JACK to do this. Its entire design is "be
woken by hardware to process N samples; process N samples; go to sleep". It
is a synchronous low latency design that does not offer scope for
processing different channels or different outputs at different times.

On Sat, Dec 3, 2016 at 7:20 PM, David Klann <dxklann@email-addr-hidden> 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
>
>
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>

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Received on Sun Dec 4 04:15:01 2016