You can import any URL <x id="START_LINK" ctype="x-a" equiv-text="<a>"/>supported by youtube-dl<x id="CLOSE_LINK" ctype="x-a" equiv-text="</a>"/> or URL that points to a raw MP4 file. You should make sure you have diffusion rights over the content it points to, otherwise it could cause legal trouble to yourself and your instance.