It is very important to control the bit-rate for video communication under a limited capacity of communication channel like wireless communication system because of large amout of data. In this paper, we propose a new adaptive pre-filter to improve the bit-rate in video compression, which preserves visually significant portion of the original image and smooth only insignificant portion actively. We focus on the differential signals between the original image and its filtered one and control the degree of smoothing by considering the power of local differential signals to produce various kinds of intermediate images betwwen both images. We conducted some computer simulations to check the performance of our scheme for the standard MPEG-4 video compression algorithm. Consequently, we could achieve further improvement of compression ratio while improving visual image quality than a conventional scheme.