Occasionally my phone records video in portrait mode instead of landscape mode.  I am trying to use Movie Maker on my Windows 8.1 laptop to import the mp4 video created by my phone and rotate it to the left 90 degrees.  The movie preview plays just fine in Movie Maker.  But when I save the video as an mp4 in Movie Maker (either computer, HD, or email resolution), the rendered video will not show the video at all (black screen) or show one frame that it alternates between black and the same frame repeatedly.  The audio plays just file.  I've tried watching the rendered video on multiple machines, all with the same result.  Even if the mp4 from my phone is imported into Movie Maker and not rotated 90 degrees, the rendered mp4 has the same problems.  Any phone videos that are in landscape mode render just fine.