1. Center for Machine Vision and Signal Analysis, University of Oulu, Oulu, Finland
2. State Key Laboratory of Media Convergence and Communication, Communication University of China, Beijing, China
3. SailYond Technology, Beijing, China
4. National Laboratory of Pattern Recognition (NLPR), Center for Biometrics and Security Research (CBSR), Institute of Automation, Chinese Academy of Sciences (CASIA), Beijing, China