Pre-processing filter apparatus for use in an image encoding system

An image encoding system for adaptively encoding an input digital video signal wherein said input digital video signal includes a plurality of frames, which comprises:

• means for delaying a current frame of the input digital video signal by one frame interval;
• means for generating a difference signal representing the difference between an averaged pixel value for N.times.N pixels (where N is a positive integer) of a previous frame which is the delayed current frame and an averaged pixel value for N.times.N pixels of the current frame, at an identical area of the previous frame and the current frame;
• two or more filtering means arranged in parallel for filtering the input digital video signal, respectively, each of said filtering means having different cutoff frequencies;
• control means for generating one of the filtered digital video signals in response to the difference signal;
• and
• means for eliminating redundancies in the generated filtered digital video signal in order to compress the generated filtered digital video signal to a manageable size for transmission thereof.