So I\'m using ffmpeg to convert a video to 1920*1080 px, I found two ways to do so, the first one would be to stretch the video to 1920*1080, but then it looks kinda stretch
Add border to all side of video with you set your padding that you want
here in input one video and add padding=20 all side left,right,top and bottom
"-i",path1,"-filter_complex","[0]pad=w=20+iw:h=20+ih:x=10:y=10:color=red; output
[0]pad=w=20+iw:h=20+ih:x=10:y=10:color=red
and same as in height h=20+ih so +20 to video height for 10 for top pad and 10 for bottom pad
x=10:y=10 is use for if x=0,y=0 so border is not show at left and top side and show border at right and bottom side of 20;