1. National Engineering Research Center of Visual Technology, School of Computer Science, Peking University, Beijing, China
2. LMAM, School of Mathematical Sciences, Peking University, Beijing, China
3. Department of Computer Science, City University of Hong Kong, Hong Kong
4. School of Information and Communication Engineering and the State Key Laboratory of Media Convergence and Communication, Communication University of China, Beijing, China
5. School of Electronic and Computer Engineering, Peking University Shenzhen Graduate School, Shenzhen, China