Hi,
I am using a Steinberg UR22 audio interface. Since installing Ubuntu 20.04 on my workstation I have slight crackling in audio playback. It doesn't matter if the audio gets routed through pulse, jack or played straight to alsa. When running jack, the crackling is not showing any xruns. It's not possible to get any glitch-free playback in the system. The onboard intel audio works fine.
My system:
alsa info: alsa-project.org/db/?f=8b821b17a8c83fa5db866f34a5b4dfe74d640a32
Processor: Intel Xeon X5687
$ uname -a
Linux WorkStation-T5500 5.4.0-56-lowlatency #62-Ubuntu SMP PREEMPT Mon Nov 23 20:19:44 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
I have tried:
5.4.0-56-generic and -lowlatency
5.8.0-31-generic and -lowlatency
setting cpu governor to performance
using nouveau driver over nvidia
When playing a file with aplay like this:
systemctl --user stop pulseaudio.socket systemctl --user stop pulseaudio.service aplay -D plughw:CARD=UR22 ./test.wav
slight crackling can be heard every 5-10 seconds. It also appears, that the clicks heard are not always on both channels, sometimes the left stereo channel clicks, sometimes the right, sometimes both.
Plugging the Interface into different USB-ports doesn't help. The only external devices connected via USB are my mouse and my keyboard. On Wndows the same setup on the same machine works fine.
To make things even weirder, using the same audio interface on my Thinkpad x220 (Core i5-2540M) with ubuntu 20.04 and 5.4.0.56-lowlatency does not show this problem.
Running dmesg seems to show nothing audio driver related after:
[ 22.425520] usbcore: registered new interface driver snd-usb-audio
I have found a similar issue showcasing the problem on manjaro with a differend soundcard. Therefore I suspect the problem is caused by ALSA interacting with the hardware.
https://forum.manjaro.org/t/pops-clicks-on-audio-interface/40129
Here is another occurence on ubuntu on yet another audio interface.
https://askubuntu.com/questions/1256787/ubuntu-2004-novation-xiosynth-extern...
If I can supply more information I'm happy to help. I couldn't find a similar issue in this mailing list, so if this is already fixed I apologize in advance.
Kilian