a method and apparatus are disclosed for performing motion estimation and compensation to fractional pixel accuracy using polyphase prediction filters as part of a video compression / decompression technique . a motion estimator applies a set of polyphase filters to some data in the reference picture and generates motion vectors , an estimated macroblock of video data , and a residual error macroblock of video data . the data referenced in the reference picture usually have more data than a macroblock since multi - tap filtering needs to access more data . a motion compensator generates a compensated macroblock of video data in response to the reference video data , the residual error macroblock of video data , and a polyphase prediction filter decided by the motion vector . the reference video data are usually reconstructed at the compensator side .