How to crop the video size when I remux a mp4

[sdf]

I am using GPAC 0.50
currently the command is:
"mp4box.exe" -add "f:\in.mp4#video" -add "f:\in.mp4#audio" "f:\out.mp4"


Now I have a mp4 file (1920x1080 H.264/AVC AAC)
In fact, the actual video size is 1440x1080, that means two black blank at left and right sides are encoded in video

so I want to set the display to 1440x1080 when I remux the mp4, I think mp4 container have such function, may I know what the command is?



besides, the two blanks are 240x1080, 240px is times of 16px, so I guess it is possible to crop the actual size to 1440 without losing any quality rather than set the display size.

am I right? if yes, may I know how?