DietPi (on RPi 3B and 4B) no 24bit audio output via HDMI

Hi folks,

first I want to say hello to all forum members. This forum is really helpful for me until now.
But after installing DietPi to attach my two Onkyo AV reveivers (PR-SC5509 and TX-NR3009) to my roon core which is running on a MacMini 2012 (Win10 on Bootcamp) I did run into the following problem:
AV 1 is connected directly to the MacMini core via HDMI. AV 2 is in another room and connected to a RPi4 with 4GB running DietPi and roon bridge also via HDMI.
I was able to set up the very helpful roon-extension-onkyo service to integrate both AV-receivers in parallel for remote control via roon.

Multichannel via HDMI is working well on both systems!

But using roon with AV 2 shows, that the RPi4 with DietPi and roon bridge downsample all 24bit audio to 16bit audio, which means a huge loss of quality.

Did I make my settings in DietPi or the RPi4 wrong or does the RPi4 (I did try it also with an RPi3b) simply not support 24bit audio via HDMI?

HDMI from the MacMini to AV 1 works up to 192kHz/24bit with no problems.

I do hope there is a solution and somebody out there will be able to help!
Thanks in advance.

Possibly hardware but maybe @Dan_Knight might be able to throw some light as DietPi is his baby

Hardware would be the worst. The Pi4 is able to play two 4k video streams via it´s two HDMI´s. Not being able to support 24bit HDMI audio would be poor :disappointed_relieved: