[LAD] Looking for some jackd debugging help

Len Ovens len at ovenwerks.net
Sun Jun 14 02:12:11 CEST 2020

On Sat, 13 Jun 2020, Ethan Funk wrote:

> That leads me to a question regarding Ubuntu Studio Control, which I have been
> using to manage jackd and additional audio interfaces via zita-a2j. I have Ubuntu
> Studio Control configured to use a Tascam US-4x4 as the main audio interface with
> 128 sample process frames at a 48 kHz sample rate on my test machine, with the
> built-in audio port on the motherboard as a a2j/j2a bridge. Audio to and from the
> motherboard interface is broken up with the zita-a2j and zita-j2a running as
> launched by Ubuntu Studio Control. Notably, the -p run option is set to 64. If I
> run zita-a2j myself with -p set nice and high, to 1024 for example, I get good
> clean audio, at the expense of latency on that interface. That's fine for me,
> since I still have good, low latency on the main interface. Does any one know
> where I can find the source code for Ubuntu Studio Control so I can investigate a
> fix to make this settable?

-controls is written in python and so easy to change. You can view the 
source directly by looking at /usr/bin/autojack. Zita-ajbridge has the 
buffer to 1/2 that of jack... but that is proving to be a problem in some 
cases. Internal should be at least 128 and hdmi should be 4096. The git 
repo is https://github.com/ovenwerks/studio-controls (it has been 
"unbranded" so other distros can feel free to use it)

This is a relatively new project and so is very much not bug free. Being 
able to directly set buffer size for each device used sounds very much 
like a reasonable feature request. (also a feature that has been thought 
of before)

Be aware that autojack runs from session start and because of the way some 
DEs use systemd/logind to start sessions... the session never really ends 
so a reboot or a killall autojack may be needed to see how changes do. I 
would suggest running autojack in a terminal while testing new code so 
that you have access to terminal output. once you have finished with the 
code running studio-controls should restart it in the background again if 
you have closed the terminal.

Len Ovens

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