1. Imaging Media Research Center, Korea Institute of Science and, Technology, 39-1 Hawolgok-Dong, Seongbuk-Gu, Seoul 136-791, Korea
2. Dept. of Computer Science &, Engineering, Korea University, 1,5-Ga Anam-Dong, Seongbuk-Gu, Seoul 136-701, Korea
3. Dept. of Computer Science & Engineering, Korea University, 1, 5-Ga Anam-Dong, Seongbuk-Gu, Seoul 136-701, Korea