I had exactly this problem with blocky playback after I upgraded from 14.04 to 16.04. It affected all movie file types and any player that I tried. After reading this report I replaced the nvideo driver 361.42 by the previous version available (340.96) - and the problem went away completely.
By the way (and I don't know how to report this so if some kind soul could do the necessary that would be good): Additional Drivers in Software and Updates, when invoked, states that No additional Drivers are in use. This is clearly false much of the time, as when it has done a search it then reports those that are in use. It should say: I don't yet know if any additional drivers are in use - please wait while I check. Not a life-threatening bug I agree, but careless coding makes it look silly. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1512993 Title: VLC exhibits blockiness on h264 seeking To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/vlc/+bug/1512993/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs