1. Department of Multimedia Engineering, Dongguk University, Seoul 100-715, Republic of Korea
2. Department of Computer Science and Engineering, Seoul National University of Science and Technology, Seoul 139-743, Republic of Korea
3. Department of Information and Communication Engineering, Fukuoka Institute of Technology (FIT), Fukuoka 811-0295, Japan
4. Humanitas College, Kyung Hee University, Seoul 130-701, Republic of Korea