On Sat, Nov 16, 2019 at 02:47:26PM -0700, Ethan Funk wrote:
1. With the low-latency kernel, jack dropouts/underruns are a problem
when jack is configured to bridge to pulseaudio. Without a pulseaudio
bridge, the dropout are nonexistent.
I'd suggest to get rid of pulseaudio. It doesn't do anything useful
for an application like yours.
Getting rid of pulseaudio is probably the right thing to do. Thanks for pushing me in that direction.
2. I have a similar issue with zita-a2j and zita-j2a with lost of
dropouts on the ALAS side, even though the jack side shows no overruns.
How does this show up (i.e. how do you know it is the ALSA side) ?
It shows up as broken audio to/from the device, with no under-runs logged by jack. All the rest of the jack audio flow is unaffected.
What do you get with the -v option ?
I don't know because I am using Ubuntu Studio Control to manage the create of zita-j2a/a2j instances on my test system. I wanted an "easy" way for potential users to set up jack and Ubuntu Studio Control is nice and easy. zita bridges are working fine on my development machine, where I manually set them up, so there must be something in how Ubuntu Studio Control is spawning the zita bridges. That's why I am also looking for the source code for Ubuntu Studio Control. Ubuntu Studio Control make jack setup supper simple, and almost a pleasure for the average user.
Can extra buffering be applied to the zita programs? Maybe that is
what the -n option is for?
Using more periods could hide the problem, but it's never a real
solution.
Are you sure things are running with real-time scheduling ?
Yes.
ps -eLfc shows FF for for the scheduling policy of at least one of the threads in the processes of interest.
This requires some configuration in /etc/security/limits.conf,
as well as for Jack itself.
I had gone down that road originally on the machine I am using for development. On my test system, I used the Ubuntu Studio Installer, which does a very nice, friendly job of setting up a stock Ubuntu machine for use with jack.
Why do you need zita-a2j/j2a anyway ? Using a single multichannel
card is usually the better solution.
I have one multichannel audio interface for everything important: program out, studio monitors, headphones, guest mic, host mic, etc. But it sure is nice to be able to use the built-in audio for a cue channel and talkback mic, where latency is not important. Also handy for USB turntables, and other random devices that are occasionally used in a radio show without latency being important.
Thanks,
Ethan...