An overlay detection unit (300) for detecting whether a particular pixe of a first image of a display sequence of video images represents a part of a graphics over ay is disclosed. The overlay detection unit (300) comprises: first testing means (302) for to ting whether a first difference (Dl 1) between a first value of the particular pixel (P(1,n)) second value of a corresponding pixel (P(l,n-1)) of a second image of the display seq ence of video images is less than a first predetermined threshold (T1); second testing mean (304) for testing whether a second difference (D22) between a third value of a second pixel (P(2,n)), being located in a spatial neighborhood of the particular pixel (P(1,n)), and fourth value of a fourth pixel (P(2,n-1)) of the second image, is less than a second predeterm'ned threshold (T2); third testing means (306) for testing whether a third difference (D12) etween the first value of the particular pixel (P(1,n)) and the third value of the second pixel ( (2,n)) is less than a third predetermined threshold (T3); and establishing means (308) for establishing that the particular pixel represents the part of the graphics overlay on bas s of the output of the testing means. |