1. Department of Multimedia Engineering, Hannam University, 133 Ojeong-Dong, Daejeok-Gu, Daejeon 306-791, Republic of Korea
2. Technical R&D Center JVG, 53, Neungwolro No. 10-Gil, Yongin-Si, Gyeonggi-Do, Republic of Korea
3. Department of Electrical and Computer Engineering, University of Florida, Gainesville, FL 32603, USA