FFPLAY

FFPLAY comes bundled with the ffmpeg download. The ffplay is a simple to use command line app for playing the extracted streams that you have just created.
The simple use of fflplay is just:

ffplay filename.mp4

However, the issue with UHD streams is that they are larger than most monitors, so it is generally necessary to either rescale the output, or force it to fullscreen.
To replay a video in a window.

ffplay -i video.mpg -vf scale=800x600
This will replay the selected file at a window size of 800x600. Remember, currently (End 2016)
UHD streams play very poorly and you will only get 1 or 2 frames per second.

To replay a video full screen.

ffplay -i video.mpg -vs
This will replay the video at fullscreen resolution.