I have been using linux since i was in college, and for me the best movie/video player for linux is the vlc player, it's far more better than totem player that came pre-installed on ubuntu 15.10 wily werewolf.
So you need to install vlc player on your ubuntu, if you want to enjoy your favorite HD movies, to install vlc movie player all you have to do is run this command from the terminal/ console/ command prompt:
sudo apt-get install vlc
If for some reasons that command above doesn't work, try updating the repository list first, here's the command:
sudo apt-get update
Unlike totem movie player that came with ubuntu 15.10, vlc player support for subtitle text, so for example you are watching japanese movie which have subtitle, the subtitle will be displayed.
There are other reasons why you should use vlc player to watch HD movie, such as faster playback and rendering, so that you will experience smooth movie playback, no lagg at all.
You can also change the aspect ratio of the video, zoom in or zoom out, cropping, add video effect, take snapshot, etc. Vlc player have so many features and options, it simply the best HD movie player, ever!!
~ cheers ~