A decoding method comprising the step of: • performing (38, 40), in units of macroblocks, motion compensation of an input image signal of an interlaced image with an accuracy of 1⁄4 pixel for a motion vector, wherein the input image signal has a format of 4: 2: 0 and includes a brightness signal and a color-difference signal, wherein each macroblock of the macroblocks comprises a top field and a bottom field, wherein a reference field in a reference macroblock of a reference frame is a top field of the reference macroblock and a current field of a current macroblock of a current frame is a bottom field for the motion compensation, and • wherein the motion compensation comprises: determining for all existing color-difference samples in the reference field, positions of new color-difference samples in the reference field, wherein the positions of the new color-difference samples are vertically shifted by mv/2 + 1⁄4 from the existing positions of the existing color-difference samples in the reference field, and generating, for each of the new color-difference samples, a value by linear interpolation, wherein the linear interpolation is done for the new color-difference sample based on the values of the two vertically adjacent existing color-difference samples, wherein mv is a vertical component of the motion vector, wherein the unit of the mv is, in the vertical direction, the distance between two adjacent brightness samples in the reference field, and the unit of the mv/2 + 1/4 is, in the vertical direction, the distance between two adjacent existing color-difference samples in the reference field. • performing (38, 40), in units of macroblocks, motion compensation of an input image signal of an interlaced image with an accuracy of 1⁄4 pixel for a motion vector, wherein the input image signal has a format of 4: 2: 0 and includes a brightness signal and a color-difference signal, wherein each macroblock of the macroblocks comprises a top field and a bottom field, wherein a reference field in a reference macroblock of a reference frame is a top field of the reference macroblock and a current field of a current macroblock of a current frame is a bottom field for the motion compensation, and • wherein the motion compensation comprises: determining for all existing color-difference samples in the reference field, positions of new color-difference samples in the reference field, wherein the positions of the new color-difference samples are vertically shifted by mv/2 + 1⁄4 from the existing positions of the existing color-difference samples in the reference field, and generating, for each of the new color-difference samples, a value by linear interpolation, wherein the linear interpolation is done for the new color-difference sample based on the values of the two vertically adjacent existing color-difference samples, wherein mv is a vertical component of the motion vector, wherein the unit of the mv is, in the vertical direction, the distance between two adjacent brightness samples in the reference field, and the unit of the mv/2 + 1/4 is, in the vertical direction, the distance between two adjacent existing color-difference samples in the reference field. determining for all existing color-difference samples in the reference field, positions of new color-difference samples in the reference field, wherein the positions of the new color-difference samples are vertically shifted by mv/2 + 1⁄4 from the existing positions of the existing color-difference samples in the reference field, and generating, for each of the new color-difference samples, a value by linear interpolation, wherein the linear interpolation is done for the new color-difference sample based on the values of the two vertically adjacent existing color-difference samples, wherein mv is a vertical component of the motion vector, wherein the unit of the mv is, in the vertical direction, the distance between two adjacent brightness samples in the reference field, and the unit of the mv/2 + 1/4 is, in the vertical direction, the distance between two adjacent existing color-difference samples in the reference field.