1 c t u2212 1 2 will cause image defects whether the color difference signal of the second preceding frame is usable or not cannot be decided from the luminance motion signal s 3 of the current frame alone in order to avoid image defects accordingly selector 19 selects the color difference input signal data cin and frame memory 11 a stores data as listed in table 6 when the luminance motion signal s 3 is set to a value indicating that motion is present the arrows in table 6 indicate that when motion is detected the data from the preceding frame are stored in both frame memories 10 a and 11 a the formula at time t 1 c t 1 u2248 c t c t u2212 1 indicates that the color difference signal data c t u2212 1 and c t 1 are substantially equal c t u2212 1 u2248 c t 1 therefore use of the averaged data c t 1 c t 2 will not cause image defects when the input video data form a moving picture the following formulas hold because the input video data form a moving picture frame memory 11 a and frame memory.