1. A method for motion estimation, comprising: generating an oriented edge image by an edge-detect-filtering process in according with contour and texture of an original luminance image; generating an subsampled edge image by performing an low-bit resolution oriented edge image process upon the edge image; performing a wide-range search upon the subsampled edge image to generate a motion vector; performing a small-range full search is performed upon the generated motion vector to obtain a final motion vector by using decoded luminance pixels.