1. A display control apparatus which projects and displays at least one image on a screen, the apparatus comprising: a conversion unit adapted to convert a frame frequency for a display of the at least one image to N times (N>1); a generation unit adapted to generate an added image by adding a predetermined pattern to the converted frame and generate a subtracted image by subtracting the predetermined pattern from the converted frame as a first frame and a second frame following the first frame; a control unit adapted to project the first frame and the second frame generated by said generation unit for an image on the screen at the N-times frequency; an acquisition unit adapted to acquire the image projected on the screen; an extraction unit adapted to extract the pattern from the image acquired by said acquisition unit; and a correction unit adapted to correct a shape of the image based on the pattern extracted by said extraction unit.