Crowd density estimation based on rich features and random projection forest

Abstract

Current state of the art crowd density estimation methods are based on computationally expensive Gaussian process regression or Ridge regression models which can only handle a small number of features. In many computer vision applications, it has been empirically shown that a richer set of image features can lead to enhanced performances. In this paper, we reason that using more image features could potentially boost the performances of crowd detection and thus propose to employ much extensive and richer feature sets for crowd density estimation. To achieve computational efficiency and scalability, we use random forest as the regression model whose tree structure is intrinsically fast and scalable. Unlike traditional approaches to random forest construction, we embed random projection in the tree nodes to simultaneously combat the curse of dimensionality and to introduce randomness in the tree construction (we call this Random Projection Forest) thus making our new method very efficient and effective. Experimental results on two public pedestrian detection video databases show that our new method achieves state of the art performances that are superior to those of previously published regression techniques.