FFMPEG -mbd parameter

[Klagar]

Hi !

I'm trying to understand FFMPEG as best I can, but some parameters still seem to elude both deduction and research.
For instance, does anyone know what the -mbd parameter is supposed to do ?

I read somewhere that setting it to "2" or "rd" makes the encoding go slower but creates a slightly less heavy output file, but that's about it. Also a lot of discussions about -mbd being supposedly related in some way to -cmp and its relatives, but most people seem to discredit this theory.

Thoughts, anyone ?

Thanks !!!