alsaloop doesn't pass sound with libsamplerate resampling on raspberry pi 5

[willangley]

Hi alsa-utils team!

I'm using alsaloops on a Raspberry Pi 5 as part of a slightly ridiculous signal chain:

• Yamaha P-525 keyboard
• USB C-to-A cable
• Raspberry Pi 5
• USB A-to-B cable
• ESI U24XL
• SPDIF in/out
• Focusrite Clarett+ 4Pre
• ...
• MacBook Pro

[Why? The analog Aux In/Aux Out on the keyboard have an always on loopback connection, which is undesirable when playing to a video meeting. The USB port has user controllable loopback.]

Two alsaloop processes run on the Pi, one moving sound from the computer to the piano, one moving sound from the piano to the computer. Both run under supervisord.

I've got them running at acceptable latency — RTL Utility says 40ms from my MacBook Pro.

But I haven't been able to get any of the high quality resampling options working -- everything other than add/drop stops passing sound within a few seconds. I'm surprised; this Pi should be powerful enough to handle this. Any ideas how to troubleshoot it?

I didn't see errors in logs at the default log level.

Thank you!
Will