[fritsch]

Btw. if you have the LG testing file in your directory:

15:56:23 T:140122838267648 DEBUG: ExtractThumb - measured 39331 ms to extract thumb from file <nfs://192.168.178.22/mnt/data/tosort/demo_files/h265/LG_4K_View-the-Feeling.mp4> in 321 packets.

that will cause 39 seconds of high load on one core - better remove it :-)

Edit: mkvmerge -o newname.mkv LG_4K_View-the-Feeling.mp4 will fix that, you need a new enough mkvutils version that can do hevc. After it is correctly converted (check file size), remove the other mp4.