Comment 10 for bug 1413771

It seems mplayer can't find the correct fps. So either it's a bug in mplayer or maybe the video is corrupted.

gnomeplayer is also a frontend for mplayer, so that's why it's also affected by the problem.

I would suggest to try mpv.

You can find here instructions to install mpv and use it with smplayer:
http://blog.smplayer.info/how-to-use-smplayer-with-mpv-in-ubuntu/