How to add black borders to video

Question

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

Answer 1

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

1. 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

2. and same as in height h=20+ih so +20 to video height for 10 for top pad and 10 for bottom pad

3. 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;

4. if we want to add border 20 so width + 40 and height + 40 and x,y = 20
5. color=red is used for border color

Answer 2

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.