1. A method of selecting a content adaptive coding mode, the method comprising: retrieving motion information for a current block and generating a high frequency band image by using the retrieved motion information; calculating a local dispersion value JND of a reference block of a reference image and calculating a sum JND sum of all local dispersion values and a sum U sum of extra data U being added to all even frames; setting a coding in screen mode when the U sum value is greater than the first critical value after comparing the calculated U sum value to a first critical value JND sum +E B ; comparing the calculated U sum value to a second critical value JND sum when the U sum value is equal to or smaller than the first critical value; maintaining a content adaptive motion compensated temporal filtering mode for a corresponding block when the U sum value is equal to or smaller than the second critical value, and adjusting the JND as a critical value of the U when the U sum value is greater than the second critical value, the JND being changed based on a pixel value in the image; proceeding an update process by using a conventional motion compensated temporal filtering method for each pixel in a block, the mode of which is not changed, wherein the E B is a sum of a tolerance range V permitted for each pixel.