The motion estimation unit ( 100 ) comprises a block-matcher ( 102 ) for calculating a start motion vector ( 110 ) by minimizing a predetermined cost function as a matching criterion for the block ( 116 ) of pixels with a further block of pixels ( 122 ) of a further image ( 120 ). The motion estimation unit ( 100 ) further comprises an optical flow analyzer ( 104 ) for calculating an update motion vector ( 111 ) based on the start motion vector ( 110 ) and which is designed to find the most appropriate set of optical flow equations corresponding to respective pixels of the block ( 116 ) of pixels. This is achieved by analyzing gradient vectors of optical flow equations for pixels of the block ( 116 ) of pixels. Finally the selector 106 of the motion estimation unit ( 100 ) selects the motion vector ( 126 ) by comparing the start motion vector ( 110 ) with the update motion vector ( 111 ).
