There is no way you can fill out a screen (change aspect ratio) of a video (or even picture) that is designed/filmed in a certain aspect ratio. You can either enlarge the entire image (stretch both up/down and left/right) and cut off something. Or you can stretch to fill in where the black bars are by distorting the image. So things will either be wider or taller than they would normally appear.
For example if I look at my older normal 4x3 photos on my TabS 10.5 there will be black bars on either side. If I try eliminating the black bars I can enlarge the entire picture but portions of the top or bottom or both will be removed. Whereas if I display a 16x9 image taken by my Blackberry Z30, there are black bars on the top/bottom. Again, I can remove them by enlarging the entire picture but now some on the left or right or both is removed.
None of these apps will allow me to distort the image by only stretching up/down or left/right but if it did the Eiffel Tower would become wider than it would normally be.