Maodi Hu

Incremental Learning for Video-Based Gait Recognition With LBP Flow

Gait analysis provides a feasible approach for identification in intelligent video surveillance. However, the effectiveness of the dominant silhouette-based approaches is overly dependent upon background subtraction. In this paper, we propose a novel incremental framework based on optical flow, including dynamics learning, pattern retrieval, and recognition. It can greatly improve the usability of gait traits in video surveillance applications. Local binary pattern (LBP) is employed to describe the texture information of optical flow. This representation is called LBP flow, which performs well as a static representation of gait movement. Dynamics within and among gait stances becomes the key consideration for multiframe detection and tracking, which is quite different from existing approaches. To simulate the natural way of knowledge acquisition, an individual hidden Markov model (HMM) representing the gait dynamics of a single subject incrementally evolves from a population model that reflects the average motion process of human gait. It is beneficial for both tracking and recognition and makes the training process of the HMM more robust to noise. Extensive experiments on widely adopted databases have been carried out to show that our proposed approach achieves excellent performance.

Combining Spatial and Temporal Information for Gait Based Gender Classification

In this paper, we address the problem of gait based gender classification. The Gabor feature which is a new attempt for gait analysis, not only improves the robustness to the segmental noise, but also provides a feasible way to purge the additional influence factors like clothing and carrying condition changes before supervised learning. Furthermore, through the agency of Maximization of Mutual Information (MMI), the low dimensional discriminative representation is obtained as the Gabor-MMI feature. After that, gender related Gaussian Mixture Model-Hidden Markov Models (GMM-HMMs) are constructed for classification work. In this case, supervised learning reduces the dimension of parameter space, and significantly increases the gap between likelihoods of the gender models. In order to assess the performance of our proposed approach, we compare it with other methods on the standard CASIA Gait Databases (Dataset B). Experimental results demonstrate that our approach achieves better Correct Classification Rate (CCR) than the state of the art methods.

Gait-Based Gender Classification Using Mixed Conditional Random Field

This paper proposes a supervised modeling approach for gait-based gender classification. Different from traditional temporal modeling methods, male and female gait traits are competitively learned by the addition of gender labels. Shape appearance and temporal dynamics of both genders are integrated into a sequential model called mixed conditional random field (CRF) (MCRF), which provides an open framework applicable to various spatiotemporal features. In this paper, for the spatial part, pyramids of fitting coefficients are used to generate the gait shape descriptors; for the temporal part, neighborhood-preserving embeddings are clustered to allocate the stance indexes over gait cycles. During these processes, we employ evaluation functions like the partition index and Xie and Benis index to improve the feature sparseness. By fusion of shape descriptors and stance indexes, the MCRF is constructed in coordination with intra- and intergender temporary Markov properties. Analogous to the maximum likelihood decision used in hidden Markov models (HMMs), several classification strategies on the MCRF are discussed. We use CASIA (Data set B) and IRIP Gait Databases for the experiments. The results show the superior performance of the MCRF over HMMs and separately trained CRFs.

View-Invariant Discriminative Projection for Multi-View Gait-Based Human Identification

Existing methods for multi-view gait-based identification mainly focus on transforming the features of one view to the features of another view, which is technically sound but has limited practical utility. In this paper, we propose a view-invariant discriminative projection (ViDP) method, to improve the discriminative ability of multi-view gait features by a unitary linear projection. It is implemented by iteratively learning the low dimensional geometry and finding the optimal projection according to the geometry. By virtue of ViDP, the multi-view gait features can be directly matched without knowing or estimating the viewing angles. The ViDP feature projected from gait energy image achieves promising performance in the experiments of multi-view gait-based identification. We suggest that it is possible to construct a gait-based identification system for arbitrary probe views, by incorporating the information of gallery data with sufficient viewing angles. In addition, ViDP performs even better than the state-of-the-art view transformation methods, which are trained for the combination of gallery and probe viewing angles in every evaluation.

A survey of advances in biometric gait recognition

Biometric gait analysis is to acquire biometric information such as identity, gender, ethnicity and age from people walking patterns. In the walking process, the human body shows regular periodic motion, especially upper and lower limbs, which reflects the individuals unique movement pattern. Compared to other biometrics, gait can be obtained from distance and is difficult to hide and camouflage. During the past ten years, gait has been a hot topic in computer vision with great progress achieved. In this paper, we give a general review and a simple survey of recent gait progresses.

Multi-view multi-stance gait identification

View transformation in gait analysis has attracted more and more attentions recently. However, most of the existing methods are based on the entire gait dynamics, such as Gait Energy Image (GEI). And the distinctive characteristics of different walking phases are neglected. This paper proposes a multi-view multi-stance gait identification method using unified multi-view population Hidden Markov Models (pHMM-s), in which all the models share the same transition probabilities. Hence, the gait dynamics in each view can be normalized into fixed-length stances by Viterbi decoding. To optimize the view-independent and stance-independent identity vector, a multi-linear projection model is learned from tensor decomposition. The advantage of using tensor is that different types of information are integrated in the final optimal solution. Extensive experiments show that our algorithm achieves promising performances of multi-view gait identification even with incomplete gait cycles.

Maximisation of mutual information for gait-based soft biometric classification using gabor features

Besides identity, soft biometric characteristics, such as gender and age can also be derived from gait patterns. With Gabor enhancement, supervised learning and temporal modelling, the authors present a robust framework to achieve state-of-the-art classification accuracy for both gender and age. Gabor filter and maximisation of mutual information are used to extract low-dimensional features, whereas Bayes rules based on hidden Markov models (HMMs) are adopted for soft biometric classification. The multi-view soft biometric classification problem is defined as two different cases, saying, one-to-one view and many-to-one view, according to the number of available gallery views. In case more than one gallery view is available, the multi-view soft biometric classification problem is hierarchically solved with a view-related population HMM, in which the estimated view angle is treated as the intermediate result in the first stage. Performance has been evaluated on benchmark databases, which verify the advantages of the proposed algorithm.

Estimation of view angles for gait using a robust regression method

The performance of most gait recognition methods would drop down if the viewpoint of test data is different from the viewpoint of training data. In this paper, we present an idea of estimating the view angle of a test sample in advance so as to compare it with the corresponding training samples with the same or approximate viewpoint. In order to obtain reliable estimation results, the view-sensitive features should be extracted. We propose a novel and effective feature extraction method to characterize the silhouettes from different views. The discrimination power of this representation is also verified through experiments. Afterwards, the robust regression method is employed to estimate the viewpoint of gait. The view angles of test samples from BUAA-IRIP Gait Database are estimated with the regression models learned from CASIA Gait Database. Compared with the ground truth angles, such estimation is satisfactory with a small error level. Therefore, it can provide necessary help for gait application systems when the view angles of test data are uncertain. This point is verified experimentally through integrating the view angle estimation into a gait based gender classification system.

Ethnicity classification based on fusion of face and gait

The recognition of ethnicity of an individual can be very useful in a video-based surveillance system. In this paper, we propose a multimodal biometric system involving an integration of frontal face and lateral gait, for the specific problem of ethnicity classification. This system performs a feature fusion to improve the discrimination of human ethnicity. Face features are extracted by means of the uniform LBP operator and gait information is characterized by a spatio-temporal representation. Afterwards, canonical correlation analysis (CCA), as a powerful tool to relate two sets of measurements, is used to fuse the two modalities at the feature level. A database including 36 walking people from East Asia and South America is built for the purpose of ethnicity classification. The experimental results show that the ethnicity recognition rate is improved by fusing face and gait information.

Cross-View Gait-Based Gender Classification by Transfer Learning

The gender of a person is easily recognized by his/her gait when training data and test data are from the same view. However, when it comes to cross-view gender classification, traditional methods can not deal with large view variation without enough labeled data in the target view. In this paper, we solve this problem by introducing a transfer learning based framework. Firstly, Gait Energy Image (GEI) of each gait sequence for all views is generated, and Principal Component Analysis (PCA) is carried out to obtain efficient gait representations. Subsequently, an inductive transfer learning approach, TrAdaBoost, is adopted to transfer knowledge from the source view to the target view, which significantly improves the performance of gait-based gender classification. Abundant experiments are conducted and experimental results demonstrate the superiority of the proposed method over traditional gait analysis methods.