Some movies such as Lawrence of Arabia 4K are too big to fit on one disc and thus when ripped create two separate MKV files.  Emby supports these multiple part movies, but merging them into one larger file is always recommended for better playback, resuming, etc. 1. Download and install MKVToolnix Click the link below if you don't already have MKVToolNix MKVToolNix Downloads – Matroska tools for Linux/Unix and Windows   2.  Open the first part of your movie