My Emby Server struggles a lot during playing x265 formatted videos, it gets stutters every 3-4 seconds. Very annoying. I resolved like this:

  • Edit /boot/config.txt: sudo vim /boot/config.txt
  • Add this line to the end
dtoverlay=rpivid-v4l2

(More details about v4l2)

  • Save the file.
  • Reboot the pi: sudo reboot now

If this doesn’t solve your problem, check out the HEVC support in your browser. The client consuming emby content should also be compatible.