How do I force 400px mode

[PigletTubeYT]

I want to force 400px mode because there is a homebrew game that runs on 800px mode and basically when i tried to record using ntr cfw it got the left side of the screen and streteched it.
The game always displays the right side but I want the game do display left.
Does anyone know how to fix this issue? (I used video player as an example)