Smile video automatically mode zoom and quality not too good

hi there , im new here. i have a little glitch with my s4 i9505 . when i switch to video mode automatically it zoom in a little. if i push on the volume button the zoom is 1. and the quality is "pixelated.." on another s4 it works find.. android 4.3 with root. any tweaks? i have a little camera screen protector but it new.. not scratched.. any ideas..?