PURPOSE: To make a boundary smooth between a moving picture and a still picture with simple configuration by providing a mixing ratio generating circuit, which calculates a mixing ratio for the outputs of three-dimensional and two-dimensional Y/G separator circuits corresponding to the output of a motion detecting circuit, and a mixing circuit executing the switch of the both separator circuits.
CONSTITUTION: In a motion detecting circuit 5, it is decided by using the difference signal between two frames of a high area signal or the difference signal in one frame of a low area luminance signal whether the picture is the moving picture or the still picture. In a mixing ratio generating circuit 6, the ratio for mixing the outputs of three-dimensional and two-dimensional Y/C separator circuits 2 and 3 is calculated corresponding to the output of the motion detecting circuit 5. A sequential circuit 23 shown in a table is inputted to memories 1 and 2. Then, the memory 1 outputs the mixing radio of the three-dimensional Y/C separator circuit and the memory 2 outputs the ratio of the two-dimensional Y/C separator circuit. When the picture is changed from the still picture to the moving picture, the state is speedily changed by three stages and an erroneous contour is prevented. Then, a change point is made smooth.