Absolute destination position. Can be outside the frame area.
Extra flag information. Currently unused.
Motion vector src_x = dst_x + motion_x / motion_scale src_y = dst_y + motion_y / motion_scale
Where the current macroblock comes from; negative value when it comes from the past, positive value when it comes from the future. XXX: set exact relative ref frame reference instead of a +/- 1 "direction".
Absolute source position. Can be outside the frame area.
Width and height of the block.