[Jack-Devel] Using USB sound card with Jack

[Benny Alexandar]

Hi,

I want to test how zita-ajbridge behaves when there is a drift in clock.
Any idea how to artificially create clock drift for testing purpose.

Any test code available in Jack audio.

-ben
________________________________
From: Jack-Devel <jack-devel-bounces at lists.jackaudio.org> on behalf of Chris Caudle <chris at chriscaudle.org>
Sent: Monday, January 15, 2018 9:58 PM
To: jack-devel at lists.jackaudio.org
Subject: Re: [Jack-Devel] Using USB sound card with Jack

On Mon, January 15, 2018 10:13 am, Benny Alexandar wrote:
> I want both PC and USB sound card ports to be accessed at the same time.

The design of jackd (really any sound server) requires it to be
synchronized to the sampling clock of the interface, and since your two
interfaces are not synchronized to each other then jackd cannot use both
at the same time without some intervention.

Using two  at the same time requires choosing one card to the be the main
backend device, then loading a sample rate converter to make the sample
stream rate to and from the secondary card(s) match exactly that of the
main card.

The packages you want are zita-alsa2jack and zita-jack2alsa, in Fedora
both come together in a package named zita-ajbridge.
This is covered in the jack FAQ, which needs to be updated, the section
describing alsa_in and alsa_out bridges is the relevant section, but those
older implementations had some problems, the zita bridges are higher
quality replacements.
http://jackaudio.org/faq/multiple_devices.html

The zita tools are included in the audio aware distributions, if you are
using a distribution which does not package them for some reason you can
get them along with the other zita applications here:
https://kokkinizita.linuxaudio.org/linuxaudio/

The jackd v1 implementation includes the equivalent of the zita bridges
internally, they need to be enabled from the command line but not loaded
as an external component.  The jackd v2 implementation (I think you said
you were using jackd 1.9.12, that is considered jackd v2) does not yet
include the zita bridges as part of the server, you will need to load them
externally.

--
Chris Caudle


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