The goal of video-based person re-identification is to recognize a person at different camera settings. Most previous methods use features from the full body to represent a person. In this paper, we propose a novel Spatial and Temporal Features Mixture Model (STFMM). Unlike previous approaches, our model first horizontally splits human body into N parts, which include the information of head, waist, legs and so on. The feature of each part is then integrated in order to achieve more expressive representation for each person. Experiments conducted on the iLIDS-VID and PRID-2011 datasets demonstrate that our approach outperforms the existing video-based person re-identification methods and significantly improves stability. Our model achieves a rank-1 CMC accuracy of 73.6 on the iLIDS-VID dataset and a rank-1 CMC accuracy of 47.8 for the cross-data testing.
Traditional methods for person re-identification mainly consist of two aspects: feature learning and metric learning. Many feature learning methods have been proposed for person re-identification in single still images or video sequences. Matsukawa al @cite_6 presented a descriptor on a hierarchical distribution of pixel features and used Gaussian distribution to describe a local image region. Liao al @cite_9 utilized the horizontal occurrence of local features and maximized the occurrence for stable representation, called Local Maximal Occurrence (LOMO). Wang al @cite_14 proposed a Discriminative Video Ranking model (DVR) to select the most discriminative video fragments, from which more reliable space-time features can be extracted. The method of Bag-of-Words (BoW) @cite_32 aimed to learn a mapping function that converted frame-wise features to a global vector. The metric learning methods have also been widely invested and made some positive achievements, such as Relaxed Pairwise Learning (RPL) @cite_26 , Large Margin Nearest-Neighbour (LMNN) @cite_11 , Relevance Component Analysis (RCA) @cite_0 , Locally Adaptive Decision Function (LADF) @cite_30 , and RankSVM @cite_10 .
@cite_30 @cite_14 @cite_26 @cite_9 @cite_32 @cite_6 @cite_0 @cite_10 @cite_11
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Person re-identification is an important technique towards automatic search of a person's presence in a surveillance video. Two fundamental problems are critical for person re-identification, feature representation and metric learning. An effective feature representation should be robust to illumination and viewpoint changes, and a discriminant metric should be learned to match various person images. In this paper, we propose an effective feature representation called Local Maximal Occurrence (LOMO), and a subspace and metric learning method called Cross-view Quadratic Discriminant Analysis (XQDA). The LOMO feature analyzes the horizontal occurrence of local features, and maximizes the occurrence to make a stable representation against viewpoint changes. Besides, to handle illumination variations, we apply the Retinex transform and a scale invariant texture operator. To learn a discriminant metric, we propose to learn a discriminant low dimensional subspace by cross-view quadratic discriminant analysis, and simultaneously, a QDA metric is learned on the derived subspace. We also present a practical computation method for XQDA, as well as its regularization. Experiments on four challenging person re-identification databases, VIPeR, QMUL GRID, CUHK Campus, and CUHK03, show that the proposed method improves the state-of-the-art rank-1 identification rates by 2.2 , 4.88 , 28.91 , and 31.55 on the four databases, respectively. Person re-identification is an important technique towards automatic search of a person's presence in a surveillance video. Two fundamental problems are critical for person re-identification, feature representation and metric learning. An effective feature representation should be robust to illumination and viewpoint changes, and a discriminant metric should be learned to match various person images. In this paper, we propose an effective feature representation called Local Maximal Occurrence (LOMO), and a subspace and metric learning method called Cross-view Quadratic Discriminant Analysis (XQDA). The LOMO feature analyzes the horizontal occurrence of local features, and maximizes the occurrence to make a stable representation against viewpoint changes. Besides, to handle illumination variations, we apply the Retinex transform and a scale invariant texture operator. To learn a discriminant metric, we propose to learn a discriminant low dimensional subspace by cross-view quadratic discriminant analysis, and simultaneously, a QDA metric is learned on the derived subspace. We also present a practical computation method for XQDA, as well as its regularization. Experiments on four challenging person re-identification databases, VIPeR, QMUL GRID, CUHK Campus, and CUHK03, show that the proposed method improves the state-of-the-art rank-1 identification rates by 2.2 , 4.88 , 28.91 , and 31.55 on the four databases, respectively. This paper introduces a new approach to address the person re-identification problem in cameras with non-overlapping fields of view. Unlike previous approaches that learn Mahalanobis-like distance metrics in some transformed feature space, we propose to learn a dictionary that is capable of discriminatively and sparsely encoding features representing different people. Our approach directly addresses two key challenges in person re-identification: viewpoint variations and discriminability. First, to tackle viewpoint and associated appearance changes, we learn a single dictionary to represent both gallery and probe images in the training phase. We then discriminatively train the dictionary by enforcing explicit constraints on the associated sparse representations of the feature vectors. In the testing phase, we re-identify a probe image by simply determining the gallery image that has the closest sparse representation to that of the probe image in the Euclidean sense. Extensive performance evaluations on three publicly available multi-shot re-identification datasets demonstrate the advantages of our algorithm over several state-of-the-art dictionary learning, temporal sequence matching, and spatial appearance and metric learning based techniques. Person re-identification is challenging due to the large variations of pose, illumination, occlusion and camera view. Owing to these variations, the pedestrian data is distributed as highly-curved manifolds in the feature space, despite the current convolutional neural networks (CNN)’s capability of feature extraction. However, the distribution is unknown, so it is difficult to use the geodesic distance when comparing two samples. In practice, the current deep embedding methods use the Euclidean distance for the training and test. On the other hand, the manifold learning methods suggest to use the Euclidean distance in the local range, combining with the graphical relationship between samples, for approximating the geodesic distance. From this point of view, selecting suitable positive (i.e. intra-class) training samples within a local range is critical for training the CNN embedding, especially when the data has large intra-class variations. In this paper, we propose a novel moderate positive sample mining method to train robust CNN for person re-identification, dealing with the problem of large variation. In addition, we improve the learning by a metric weight constraint, so that the learned metric has a better generalization ability. Experiments show that these two strategies are effective in learning robust deep metrics for person re-identification, and accordingly our deep model significantly outperforms the state-of-the-art methods on several benchmarks of person re-identification. Therefore, the study presented in this paper may be useful in inspiring new designs of deep models for person re-identification.