In one embodiment, the method includes determining reference picture index numbers in a reference picture list. The reference picture index numbers increase for reference pictures having a decreasing display order with respect to a picture including the macroblock, and the reference picture index numbers increase for reference pictures having an increasing display order with respect to the picture including the macroblock. The reference picture index numbers of the reference pictures having a decreasing display order are greater than the reference picture index numbers of the reference pictures having an increasing display order. The method further includes reordering the reference picture index number allocated to each reference picture in the reference picture list, obtaining a field reference picture index associated with the current field macroblock, determining a frame reference picture index based on the field reference picture index and the reference picture index numbers, and selecting a field reference picture having a parity different from a parity of the field macroblock when the field reference picture index is odd value.