Save a copy of the original somewhere else, like the desktop in a separate folder, just in case. Rename the downloaded file to "BG_LoginVideo_01.bk2" Once you rename the file just place it into the movies folder.
You can also use it for heist loading screens if you copy it and change it to the loading screen name like "HeistBG_ArmoredTransport.bk2" Happy Heisting! I feel like this might work better as a loading screen.