The study of human gait has become a popular  and dynamic research focus in computer vision in recent years, thanks to its promising applications in many areas. Numerous gait analysis systems with diversified applications have been proposed and implemented with progressing complexity and accuracy. This paper surveys recent video-based gait analyses, which are quite challenging but promising. Three main subjects are covered in this survey: first, we describe a typical video-based gait analysis system; second, we present the processing steps in the system based on the recent video-based gait-analysis papers; finally, we indicate the key problems and future research directions of the field.