This gist installs the newest mesa driver inside a emby docker container
Go inside the docker container:
docker exec -it emby /bin/bash
curl -s -L https://gist.githubusercontent.com/JBou/41a19db4c513d7acc7f6b97d151da7ff/raw/emby_install_mesa.sh | bash
Afterwards you have to go to Diagnostic Options -> FFmpeg Options on the Emby Admin Dashboard and change the following parameters: