1. A method for reconstructing full-resolution frames from a line-skipped-sequence of fields, the method comprising: receiving a target field and at least one reference field of the line-skipped sequence; up-sampling a target block of the target field in the vertical direction by merging the lines of the target block and the lines of a reference block of the at least one reference field; determining a smoothness value indicating smoothness of pixel data of the up-sampled target block; and determining a position of the reference block within the at least one reference field in accordance with the determined smoothness value so as to optimize the smoothness of the up-sampled target block, wherein in the determining of the position, the position is determined so as to optimize the smoothness value, and in the up-sampling in the vertical direction, the merging is performed using the reference block at the position determined in the determining of the position so as to optimize the smoothness value.