FFmpeg pad Filter: Letterbox and Pillarbox Video for Any Aspect Ratio

FFmpeg's pad filter can add black or colored bars to a video to fit it into a specific aspect ratio without distorting the image. This is useful for videos with different aspect ratios, such as 4:3 to 16:9 or 9:16. To use the pad filter, you can specify the total canvas size, position the video, and set the color of the empty space. You can also use built-in variables to center the video on the target canvas. This can be automated through an API call. However, be aware that padding without scaling first can cause errors if the input is larger than the pad dimensions, and odd dimensions can break H.264/H.265 encoding.