1. A digital image signal processing apparatus, to which an input digital image signal is input, said digital image processing apparatus comprising: storing means for storing a digital image signal; extracting means for extracting a signal representing a specific area from the digital image signal stored in said storing means; detecting means for detecting a motion of the specific area based on the input digital image signal and the extracted signal representing the specific area; and synthesizing means for synthesizing the input digital image signal and the extracted signal representing the specific area so as to align the position of the extracted specific area and the position of a corresponding area represented by the input digital image signal; wherein said storing means updates the digital image signal stored therein with an output signal supplied from said synthesizing means.