I. Introduction
Crowd counting is to count the number of people in a specific area. It is of great value in public, and crowd counting is also an important research topic in the field of computer vision and intelligent video surveillance. It aims to build a high-performance cognitive system for crowd monitoring and scene understanding [1]-[3]. First, it has a huge benefit of social management and safety. For example, monitoring the flow of people in a square or a mall in a festival to prevent accidents[4], [5]. Meanwhile, the research on the crowd also has a certain economic effect. For example, investigating the crowd of people in a mall could be used to determine their business capabilities. Moreover, the study of crowd counting also affects other different subjects like psychology [6] and biology [7], [8].