1. Department of IE, The Chinese University of Hong Kong, HKSAR, China
2. National Engineering Laboratory for Big Data Analysis and Applications, Peking University, Beijing, China
3. SenseTime Research, Shanghai, China
4. Shanghai AI Lab, Shanghai, China
5. Department of Electronic Engineering, Tsinghua University, Beijing, China
6. School of EECS, Peking University, Beijing, China
7. Department of Information Engineering, The Chinese University of Hong Kong, Hong Kong, China