Video signal control apparatus, a video signal control method, and a display device

Black line insertion part (3), a certain number of frames of the video, the gradation lines having color and thickness of the predetermined number of pixels of constant gray, at regular intervals in a row or column direction of the image to insert Te. Further, the image of the next predetermined number of frames, inserts the gradation line position corresponding to the position where the line is not inserted in the video of the predetermined number of frames.