A motion vector (MV) projection method includes generating motion field motion vectors (MFMVs) for a first portion of a current frame by applying MV projection to MVs of a portion of each of reference frames and storing the MFMVs of the first portion of the current frame into an MFMV buffer, and generating MFMVs for a second portion of the current frame by applying MV projection to MVs of a portion of each of the reference frames and storing the MFMVs of the second portion of the current frame into the MFMV buffer. The second portion does not overlap the first portion. Before generating the MFMVs for the second portion of the current frame is done, at least one of the MFMVs of the first portion is read from the MFMV buffer and involved in motion vector determination of at least one coding block included in the first portion.