The Jellyfin maintainers effort now lead to this really good implementation of mpp in ffmpeg:
The wiki of this project covers everything regarding compilation, decoding, encoding, video filters and transcoding with ffmpeg.
For a HW accelerated Jellyfin there is a docker run command:
docker run -d \
--name jellyfin \
--privileged \
--net=host \
--restart=unless-stopped \
--volume /path/to/config:/config \
--volume /path/to/cache:/cache \
--volume /path/to/media:/media \
`for dev in dri dma_heap mali0 rga mpp_service \
iep mpp-service vpu_service vpu-service \
hevc_service hevc-service rkvdec rkvenc vepu h265e ; do \
[ -e "/dev/$dev" ] && echo " --device /dev/$dev"; \
done` \
nyanmisaka/jellyfin:latest-rockchip