Audio distortion problem

[michaeldessen]

Thanks again for all the work on this, @kdoren! I’ve been setting up some more student groups on Pi4s with jambox to use Sonobus, with the hifiberry card modifications described in discussion #23 . Overall it’s working but in some cases, someone's audio is severely distorted (sounds kind of like a sample rate mismatch). In a couple cases today I was able to solve it by first (before opening Sonobus) opening Qjackctl, where I saw that Jack was already running with frames/period set at 1024, and stopping Jack, setting frames/period to 64, restarting Jack there, then opening Sonobus (which by default is set to use a buffer of 64). Then it worked. But in other cases it worked fine from the start with no distortion, even though when I checked Qjackctl, Jack was running with the same 1024 setting (even while Sonobus was running with a buffer of 64).

I'll be testing with some more devices in the coming days but this is really strange because I can't reproduce the problem at all on my own Pi device, and it's intermittent even for the users that experience it, and doesn't affect everyone.

Any ideas of what might be causing this or other steps to troubleshoot? Many thanks!

[kdoren]

@michaeldessen A few thoughts.

1. SonoBus has its own setting for "Audio Buffer Size" which needs to match the PERIOD setting in /etc/jackdrc.conf. In Jambox image, these both default to 64. If this setting got changed in /etc/jackdrc.conf but not in SonoBus, it could cause symptoms like the ones you are seeing.
2. Does Jamulus work or is the problem specific to SonoBus?
3. Don't use qjackctl (I only included it in case anyone wanted to use it to change patches, but patchage is better for that). The device settings are controlled in the file /etc/jackdrc.conf, which is sourced when you start Jamulus or SonoBus. ("sudo retext /etc/jackdrc.conf" to edit).
4. What are your settings for PERIOD and NPERIODS? If you are getting bad distortion, try increasing NPERIODS. hifiberry should be stable with PERIOD=64 and NPERIODS=4,
5. If all else fails, you might want to try flashing a new SD card with the Jambox image (or swap card with working unit) and see if the problem goes away; maybe a setting got corrupted.
6. This is unrelated, but FYI there have been reports of issues with SonoBous using multiple peers; there is a workaround (updated start script) described in this thread: Network errors during Sonobus sessions #17

[michaeldessen]

Thanks so much for the quick reply, Kevin!

I did already check the jackdrc.conf file and it seemed fine (PERIOD=64 and NPERIOD=8) and Sonobus buffer was correctly set to 64, too. I only checked Qjackctl one dayin order to test jacktrip (which worked perfectly BTW) and thought it was strange that Jack was already running when I opened Qjackctl, but with a different frames/period (1024) than the default set in jackdrc.conf (which I thought would control the Jack setttings whenever Jack was started). So I thought that might be a clue, and with one case where the distortion appeared, resetting the Jack settings in the Qjackctl setup window and restarting Jack there, then starting Sonobus, solved it. But it's been intermittent so I'm not confident that was really what fixed it, and wonder if maybe it's related to the Sonobus thread you mention above and/or updating the Sonobus version.

I haven't tried Jamulus at all but will do that if needed for more troubleshooting.

I'll try all that and report back. Many thanks!