Re: [LAU] "Skewed" Audio with JACK

Hmm, I use Debian Testing, with JACK and a USB sound card (for both recording and playback) also using Audacity and jack-record. I don't have Pulseaudio installed at all. And I've never had left-right channels out of sync by even two samples.

Don't know what's going on with your setup. Perhaps try booting the machine from an audio-oriented distro like Musix 3, KXStudio, or ArtistX and see if you have same problem?

David W. Jones
gnome@hawaii.rr.com
authenticity, honesty, community
http://dancingtreefrog.comOn Dec 3, 2016 13:59, Paul Davis <paul@linuxaudiosystems.com> wrote:
>
> 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@gmail.com> 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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>> Linux-audio-user@lists.linuxaudio.org
>> http://lists.linuxaudio.org/listinfo/linux-audio-user
>>
>
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Received on Sun Dec 4 08:15:01 2016