1. A method for use in encoding video data in a video encoder, the method comprising: making a spatial/temporal motion vector prediction decision for at least one direct mode macroblock in a B-picture, wherein the spatial/temporal motion vector prediction decision indicates use of spatial motion vector prediction for the at least one direct mode macroblock; selectively encoding the at least one direct mode macroblock, wherein the encoding includes for a given direct mode macroblock of the at least one direct mode macroblock: selecting a reference picture for the given direct mode macroblock from among reference pictures used for surrounding portions of the B-picture, wherein the selecting the reference picture for the given direct mode macroblock comprises selecting a minimum reference picture index for the given direct mode macroblock from among the reference picture indices used for the surrounding portions of the B-picture; performing spatial motion vector prediction for the given direct mode macroblock; and performing motion compensation for the given direct mode macroblock; and signaling spatial/temporal motion vector prediction decision information for the at least one direct mode macroblock in a header that includes header information for plural macroblocks in the B-picture, wherein the signaling of the spatial/temporal motion vector prediction decision information in the header communicates to a video decoder the spatial/temporal motion vector prediction decision for the at least one direct mode macroblock.