making a transcoded video filling up the screen

[HeyRicardo]

When I open videoclips (at different WxH res like 928x522 or 768x432) they are able to go fullscreen on a FHD tv.
In this case I am asking about, after recording by the smartphone at lower resolution (540p) I used VLC to rotate it in landscape view, but when I view the transcoded video it doesn't enlarge, so I have a centered rectangle and background solid color around.
What have I missed in transcoding, so as to have it enlarge and fit the screen?