Only change I've made to my setup is updating to TVOS 17 for Apple TV4k.
Video plays fine, and if I select within TVOS17 for example sound output to bluetooth headphones, I get audio all ok. [Video uploaded locally to the Apple TV storage], so this doesn't 'appear' to be a bluetooth issues given BT Headphones are working fine for output.
TVOS 17 sound settings - have experimented with modifying these, no difference, usually are set to optimal quality ie unmodified.
There's no issue with the .MKV file, I can play the same .MKV video locally on a Mac with VLC, [Ventura 13.6] and set sound output to airplay to the HomePods and it works fine.
Just simply no sound output when using VLC app v 3.4.9 on TVOS17, to HomePods [yes Apple TV is on same network as HomePods, and original HomePods product version if that matters].
All other apps installed on the Apple TV4k device are playing sound to HomePods without issue
Have done the usual stuff - deleted all local files uploaded , deleted VLC app, restarted system, re-installed VLC, re-uploaded the .MKV file to local storage on the Apple TV.
I have also converted the same .MKV file to .MP4 in Handbrake, and the .MP4 version still presents the same issues with sound.
Thanks in advance for any resolution tips!