If you want to make sure that no bits are wasted for encoding the transitions from picture to borders within a macroblock, you should crop and add borders such that the active picture and the added borders become mod16. I some cases this means that you might have to crop a few pixels into the active picture. - resize to DVD resolution - crop such that the active picture is mod16 (a multiple of 16) - add borders (which also need to comply with mod16 rule) - encode