[pulseaudio-discuss] iec958 (S/PDIF) + USB = 100% CPU usage

[Sean Greenslade]

On Fri, Sep 08, 2023 at 11:00:35AM -0600, Ismael Farfán wrote:
> Hi Sean
> 
> I noticed it only happens when using 5.1 audio and something is playing.
> It triggers 100% usage from 1 core, not the whole CPU
> So this causes the issue : Digital Surround 5.1 (IEC958/AC3)
> But the stereo ones doesn't: Digital Stereo (Duplex) (IEC958)

Ah, well, I don't have any 5.1 channel hardware, so I can't test this.
Sorry.

> I'll try updating my kernel from backports and see if I can squeeze more
> logs.
> 
> I haven't found how to get only pulse audio logs from journalctl
> journalctl --user _SYSTEMD_UNIT=pulseaudio.service

That should be the correct command. I'm not sure why that isn't
returning the logs. If all else fails, you could try killing the
systemd pulse service and running the pulseaudio server manually in a
terminal to capture the logs.

> I'll come back when I get more info about this issue, may actually try with
> arch :v
> 
> systemctl status --user pulseaudio
> sep 08 08:17:39  pulseaudio[1822]: Failed to open module
> module-zeroconf-publish.so: module-zeroconf-publish.so: cannot open shared
> object file: No such file or directory
> sep 08 08:17:39  pulseaudio[1822]: Failed to open module
> "module-zeroconf-publish".
> sep 08 08:17:39  pulseaudio[1822]: module-rescue-stream is obsolete and
> should no longer be loaded. Please remove it from your configuration.
> sep 08 08:17:39  pulseaudio[1822]: Failed to open module
> module-zeroconf-publish.so: module-zeroconf-publish.so: cannot open shared
> object file: No such file or directory
> sep 08 08:17:39  pulseaudio[1822]: Failed to open module
> "module-zeroconf-publish".
> sep 08 08:17:39  pulseaudio[1822]: Module "module-rescue-streams" should be
> loaded once at most. Refusing to load.
> sep 08 08:17:39  systemd[1806]: Started pulseaudio.service - Sound Service.
> sep 08 08:17:39  pulseaudio[1822]: Could not find
> org.bluez.BatteryProviderManager1.RegisterBatteryProvider(), is bluetoothd
> started with experimental features enabled (-E flag)?
> sep 08 10:28:35  pulseaudio[1822]: Got POLLNVAL from ALSA
> sep 08 10:28:35  pulseaudio[1822]: Error opening PCM device
> plug:SLAVE='a52:3': No such file or directory

No smoking gun in these logs that I can see. You could try to turn up
the log verbosity, though I don't really know if that will shed any
additional light on the issue.

--Sean