ALSA is limited to 16/48k via HDMI which makes the Raspberry Pi based Roon Bridge a very poor choice for multichannel audio.
Doing some digging, I discovered OpenMAX which allows for the audio decode to bypass ALSA and access the Broadcom HDMI (MMAL) directly. This would allow for high resolution on all channels and, therefore, turning the Raspberry Pi into an excellent multichanel Roon Bridge. It would require a special version of Roon Bridge though.
I expect this post to go nowhere other than to bring this info to the Roon folks. I will probably replace my multichannel Pi based bridge with a tiny Windows machine (the horror) at some point. I would prefer to not have to do that though which is why I keep searching for solutions. Any chance of open sourcing the Bridge software? Maybe this could be a community driven effort?
Thanks for reading. Enjoy your day.