Very High CPU with playback

[rainman]

Hi I am new to Jellyfin and containers on NAS so am hoping some kind soul can guide me in the right direction.

I am running a Synology 920+ NAS with 20GB RAM with Jellyfin 10.9.9 installed in a container.

As soon as I start playback on a video file (playing back in a firefox browser on a Macbook Pro) the NAS CPU shoots up to almost 100%.  The video runs ok but I am concerned about the over use of CPU.

Here is a link to the transcode log: https://pastebin.com/icdbDSiy

Any help would be much appreciated. Thanks.