Synology Docker Transcoding Problem

[raccoonsummer]

I have this working on a Synology DS920+ -- can't remember where I found the guide, but you need to set the permissions on /dev/dri/your render device, then also pass that hardware device to the docker container.

Set up a scheduled task in synology to run a user-defined script:
task name: Set dev-dri-renderD128 Permission for Jellyfin
User: root
Event: boot-up
Task settings>run command>user-defined script: chmod 666 /dev/dri/renderD128

Note: your render device may be different.

Then, in your jellyfin docker-compose.yml add (section alongside volumes, ports, etc):
    devices:
      - /dev/dri:/dev/dri