display system 300 further includes an identical frame detector 38 the identical frame detector 38 is configured to analyze the image characteristics of the side by side frames sbs 1 sbs n and sbs 1 u2032 sbs n u2032 for a predetermined period of time thereby identifying the corresponding frame pairs in the upsampled 2d video signal s 2 next the identical frame detector 38 may instruct the 2d 3d converter 26 to begin format conversion and the shutter control 28 may operate the lenses of the shutter glasses 240 in sync with respective left eye and right eye images fig7 is a diagram illustrating the operation of the 3d display device 320 according to the present invention the identical frame detector 38 may perform image analysis on the upsampled 2d video signal s 2 for a predetermined period of time such as on the first n frame pairs sbs 1 sbs 1 1 sbs 2 sbs 2 u2032 sbs n sbs n u2032 n is an integer smaller than n for identifying the corresponding frame pairs based on checksum or histogram of the side by side frames or based on other image characteristics well known to those skilled in the art for any three consecutive side by side frames such as sbs 1 sbs 1 u2032 and sbs 2 in the upsampled 2d video.