Jellyfin eats all ram

[Fate]

I'm running 10.9.9 and after setting the Parallel library scan tasks limit to 4 I'm having the same problem.
Trickplay is disabled and I think the problem is that ffmpeg uses 1G each thread

Can I limit the maximum memory used bt ffmpeg?
Any help would be appreciated.

You can not really limit the RAM ffmpeg will use. It will use the Ram necessary to do the job, not more not less.

Also it is not using 1gig each thread. Your own screenshot shows that.
The threads use 5.8% , 2.7% , 8.6% an 12.3% of your memory.
So combined 29,4% of your memory. If you have 4gig that would be 1205MB combined.

How about you share a screenshot of atop without any cover so we can see what your system is doing?