FFAStrans wiki

This filter allows you to remove lines from left, right, top and bottom of the video.

Left, Right, Top, Bottom

Valid values are integers from 0 and up. If you are using the "Custom FFmpeg" encoder, you should make sure the value is divisable by 2. Otherwise some encoders may choke.

Maintain frame size

If you check this option, FFAStrans will fill the cropped area with the color of your choice. Thus the full original frame size will be retained.