My guess is you are using fit to screen on media player and it is jacking up the aspect ratio giving you the impression that it's one way when it's really the other. I.e. In the screen cap below, when you play this in windows media player, do you actually see the edges of both fenders? Or do you just see the same thing, just stretched out?
If you see the same thing, then you held the video camera the wrong way. If you can actually see both fenders at the same time in the video on your computer, then somehow you cropped the video when sending it to youtube.