Your two definitions should be Landscape = 'laying down' & Portrait = 'standing up'.
Rule #1 for video is never use portrait, as everybody watches in landscape.
Your only solutions are to shrink to fit, which is what you've done, leaving black borders; or crop & zoom, effectively chopping off the top & bottom of the picture, so the rest fills the screen.
See The Magic of Crop, Pan, Zoom, and Rotate on the Sony site