1. A method for transforming video information using a computing device that implements a video encoder and/or decoder, the method comprising: with the computing device that implements the video encoder and/or decoder: checking a hybrid motion vector prediction condition based at least in part on a predictor polarity signal applicable to a motion vector predictor for a block or macroblock of a current interlaced forward-predicted field, wherein the predictor polarity signal is for selecting dominant polarity or non-dominant polarity for the motion vector predictor, and wherein the dominant polarity is opposite polarity or same polarity depending on whether motion vectors of plural neighboring blocks or macroblocks in the current interlaced forward-predicted field predominantly reference: an opposite polarity reference field having opposite polarity as the current interlaced forward-predicted field, or a same polarity reference field having same polarity as the current interlaced forward-predicted field; and determining the motion vector predictor.