AutoFit

Pad the output (with either letterbox or pillar box) to honor the output resolution, while ensuring that the active video region in the output has the same aspect ratio as the input. For example, if the input is 1920x1080 and the encoding preset asks for 1280x1280, then the output will be at 1280x1280, which contains an inner rectangle of 1280x720 at aspect ratio of 16:9, and pillar box regions 280 pixels wide at the left and right.