How to add black borders to video
Use
-vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2,setsar=1"
The scale will ensure that its output fits within 1920x1080. The pad then fills that out.
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
- Here, w=20+iw means your video width + 20 because you want add border so we need to add padding 20 for 10 right side pad and 10 left side pad
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;
- if we want to add border 20 so width + 40 and height + 40 and x,y = 20
- color=red is used for border color
