Automatic gait recognition based on statistical shape analysis

Gait recognition has recently gained significant attention from computer vision researchers. This interest is strongly motivated by the need for automated person identification systems at a distance in visual surveillance and monitoring applications. The paper proposes a simple and efficient automatic gait recognition algorithm using statistical shape analysis. For each image sequence, an improved background subtraction procedure is used to extract moving silhouettes of a walking figure from the background. Temporal changes of the detected silhouettes are then represented as an associated sequence of complex vector configurations in a common coordinate frame, and are further analyzed using the Procrustes shape analysis method to obtain mean shape as gait signature. Supervised pattern classification techniques, based on the full Procrustes distance measure, are adopted for recognition. This method does not directly analyze the dynamics of gait, but implicitly uses the action of walking to capture the structural characteristics of gait, especially the shape cues of body biometrics. The algorithm is tested on a database consisting of 240 sequences from 20 different subjects walking at 3 viewing angles in an outdoor environment. Experimental results are included to demonstrate the encouraging performance of the proposed algorithm.     

Human gait recognition in canonical space using temporal templates

A system for automatic gait recognition without segmentation of particular body parts is described. Eigenspace transformation (EST) has already proved useful for several tasks including face recognition, gait analysis, etc; it is optimal in dimensionality reduction by maximising the total scatter of all classes but is not optimal for class separability. A statistical approach that combines EST with canonical space transformation (CST) is proposed for gait recognition using temporal templates from a gait sequence as features. This method can be used to reduce data dimensionality and to optimise the class separability of different gait sequences simultaneously. Incorporating temporal information from optical-flow changes between two consecutive spatial templates, each temporal template extracted from computation of optical flow is projected from a high-dimensional image space to a single point in a low-dimensional canonical space. Using template matching, recognition of human gait becomes much faster and simpler in this new space. As such, the combination of EST and CST is shown to be of considerable potential in an emerging new biometric     

基于能量图分解与运动偏移特性的步态识别

提出一个新的步态识别算法.首先通过计算轮廓图距离来检测异常步态轮廓图,并利用平均近邻图与平均轮廓图重建异常的图像.然后将对象的步态能量图分解为两部分,并分别为每一部分生成一系列扩展图像,从而构造出能量分解图.接着根据主干图与步态偏移图的对应关系消除静态形状信息,并进行脚部区域校正,从而构造出运动偏移图.最后,使用能量分解图和运动偏移图共同进行分类.实验结果表明,本文算法的识别率远远高于3个典型算法.     

基于最优轴投影特征的步态识别

提出了一种最优轴投影(OAP)特征来描述步态信息。首先用背景减除法得到序列图像中的轮廓,然后随机选一部分轮廓样本基于主成分分析(PCA)方法训练出最优轴,并基于最优轴提取每个轮廓点的OAP特征。在UCSD和SOTON数据库的实验结果显示,OAP特征包含了丰富的步态信息;和同类型方法相比,本文方法有较高的识别率,计算复杂度减小,识别速度提高。     

一种基于Radon变换的微表情识别算法

微表情是人们处在一些与平时生活环境不同的高强度环境下试图控制和掩饰的情感表现,也是一种不曾意识到的瞬时脸部表情,持续时间短,强度弱。为了提高其准确率,提出了基于Radon变换的微表情识别算法。首先,对数据库中的视频序列进行灰度归一化、尺寸归一化和二维主成分分析法(Two-dimensional Principal Component Analysis,2DPCA)降维预处理,使用光流法对降维后图像提取运动特征;然后使用Radon变换算法对光流图像进行处理,得到对应微表情的特征值和特征图像;最后使用支持向量机进行微表情分类识别。实验结果表明,使用Radon变换后得到的微表情特征图像得到了较好的识别效果,在微表情数据集CASME和CASMEⅡ上识别率分别为81. 48%和82. 17%,通过与选取的其他方法对比说明了该方法具有更好的识别性能。     

远距离复杂背景鲁棒的步态特征提取与表示方法

远距离复杂背景下步态图像通常受到噪声的影响很大。Gabor特征在此类步态识别中显示了良好的特性,然而一些基于Gabor特征的算法使用较多的模板从而导致计算量增大。为解决这个问题,本文提出了一种新的基于改进Gabor特征的步态特征提取与表示方法。首先突出步态能量图中的有效区域,并抑制易受噪声干扰的区域。然后构造一个同时具有两个方向互补特性的基本的滤波器,经过缩放和旋转,生成一系列滤波器。使用这些滤波器对改进的步态能量图以及步态差异图像进行卷积,得到两个特征向量集合以表示此步态对象。使用最近邻分类计算出本文方法在USF步态数据库上的识别率,与相关算法的比较证实了此步态特征提取与表示方法的有效性。对算法的计算量分析表明,本文算法所需的计算量比相关算法有较大降低。      

Gait recognition using Pose Kinematics and Pose Energy Image

Many of the existing gait recognition approaches represent a gait cycle using a single 2D image called Gait Energy Image (GEI) or its variants. Since these methods suffer from lack of dynamic information, we model a gait cycle using a chain of key poses and extract a novel feature called Pose Energy Image (PEI). PEI is the average image of all the silhouettes in a key pose state of a gait cycle. By increasing the resolution of gait representation, more detailed dynamic information can be captured. However, processing speed and space requirement are higher for PEI than the conventional GEI methods. To overcome this shortcoming, another novel feature named as Pose Kinematics is introduced, which represents the percentage of time spent in each key pose state over a gait cycle. Although the Pose Kinematics based method is fast, its accuracy is not very high. A hierarchical method for combining these two features is, therefore, proposed. At first, Pose Kinematics is applied to select a set of most probable classes. Then, PEI is used on these selected classes to get the final classification. Experimental results on CMU's Mobo and USF's HumanID data set show that the proposed approach outperforms existing approaches.     

一种基于主曲线的步态识别方法

提出将主曲线作为一种新的步态特征分析和分类方法.主曲线特征分析单独分析每类样本的特征,形成直接对各类样本特征及其趋势的低维流形描述,保留了数据集的内在拓扑结构.首先对步态序列时空分析,在低的代价下表达步态运动的时空变化模式;然后,对步态特征进行主曲线分析;最后,用针对该分析方法定义的新相似性度量和分类规则进行了步态的训练和识别.在常用数据库上的测试结果表明,本方法行之有效,主曲线具有很好的实用性.     

Human recognition system for outdoor videos using Hidden Markov model

Human recognition is an essential requirement for human-centric surveillance, activity recognition, gait recognition etc. Inaccurate recognition of humans in such applications may leads to false alarm and unnecessary computation. In the proposed work a robust background modeling algorithm using fuzzy logic is used to detect foreground objects. Three distinct features are extracted from the contours of detected objects. An unique aggregated feature vector is formed using a fuzzy inference system by aggregating three feature vectors. To minimize computation in recognition using Hidden Markov model (HMM), the length of final feature vector is reduced using vector quantization. The proposed method is explained using five basic phases; background modeling and foreground object detection, features extraction, aggregated feature vector calculation, vector quantization, and recognition using Hidden Markov model.     

用于步态识别的多层窗口图像矩

该文提出了一种以局部性矩统计量作为步态特征描述的步态识别方法。首先提取行人二值轮廓序列,构造一种基于直方图的轮廓点分布特征检测出步态周期;然后生成彩色步态运动历史图像CGHI描述步态的空间特征和时间信息;继而设计了多层同心矩形窗口分割CGHI,提取出一组矩形环窗口的矩特征量作为步态特征,在此基础上实现了步态识别。在Soton数据库上进行了实验,提出算法的正确识别率可达87.2%,优于现有方法。     

基于多层运动历史图像的飞行时间相机人体运动识别

该文利用飞行时间(Time-Of-Fligh, TOF)相机提供的距离图像,在运动历史图像的基础上提出一种基于多层运动历史图像的人体运动识别方法。计算距离轮廓序列的运动能量图作为整体运动信息,同时根据距离变化量,计算前向、后向的多层运动历史图像作为局部运动信息,共同组成多层运动历史图像。为了解决Hu矩对不连续或具有噪声的形状较为敏感的问题,引入R变换对每层运动历史图像进行特征提取,串联形成特征向量送入SVM进行分类识别。实验结果表明,该识别方法可以有效识别人体运动。     

Isolated Mandarin syllable recognition using segmental features

A segment-based speech recognition scheme is proposed. The basic idea is to model explicitly the correlation among successive frames of speech signals by using features representing contours of spectral parameters. The speech signal of an utterance is regarded as a template formed by directly concatenating a sequence of acoustic segments. Each constituent acoustic segment is of variable length in nature and represented by a fixed dimensional feature vector formed by coefficients of discrete orthonormal polynomial expansions for approximating its spectral parameter contours. In the training, an automatic algorithm is proposed to generate several segment-based reference templates for each syllable class. In the testing, a frame-based dynamic programming procedure is employed to calculate the matching score of comparing the test utterance with each reference template. Performance of the proposed scheme was examined by simulations on multi-speaker speech recognition for 408 highly confusing isolated Mandarin base-syllables. A recognition rate of 81.1% was achieved for the case using 5-segment, 8-reference template models with cepstral and delta-cepstral coefficients as the recognition features. It is 4.5% higher than that of a well-modelled 12-state, 5-mixture CHMM method using cepstral, delta cepstral, and delta-delta cepstral coefficients     

Robust gait recognition via discriminative set matching

In this paper, we propose a framework for gait recognition across varying views and walking conditions based on gait sequences collected from multiple viewpoints. Different from most existing view-dependent gait recognition systems, we devise a new Multiview Subspace Representation (MSR) method which considers gait sequences collected from different views of the same subject as a feature set and extracts a linear subspace to describe the feature set. Subspace-based feature representation methods measure the variances among samples, and can handle certain intra-subject variations. To better exploit the discriminative information from these subspaces for recognition, we further propose a marginal canonical correlation analysis (MCCA) method which maximizes the margins of interclass subspaces within a neighborhood. Experimental results on a widely used multiview gait database are presented to demonstrate the effectiveness of the proposed framework.     

基于改进的加权累积差分法的人体行为识别*

针对两帧差分法和三帧差分法难以提取到完整的运动剪影,本文提出了一种基于改进的加权累计差分法的人体行为识别方法。通过使用改进的加权累计差分法能通过计算帧的相似度,用于对权值进行自适应变化,从而提取到较为完整的人体运动剪影,然后采用提出的关键帧的模板选取方法和分块特征提取来进行行为的特征提取,最后利用支持向量机构造分类器进行识别。实验结果表明采用改进的加权累积差分法能有效提高人体行为识别率。     

基于人体关节点的步态识别算法研究

步态识别是指根据人走路的方式及动力学特征来识别人的身份。人体关节点能很好地表征步态特征。本文提出一种的新的算法：用半周期长的代表性短序列取代关键帧,然后对每个序列用下肢关节角度描述其动态特征,并用关节点的形状上下文描述其轮廓静态特征,较好的提取了人体的步态信息。我们通过实验,对不同特征赋予相应权值进行特征融合,并采用K近邻分类器有效地提高了识别率。实验表明,该算法具有很好的识别效果。     

Radar HRRP target recognition based on higher order spectra

Radar high-resolution range profile (HRRP) is very sensitive to time-shift and target-aspect variation; therefore, HRRP-based radar automatic target recognition (RATR) requires efficient time-shift invariant features and robust feature templates. Although higher order spectra are a set of well-known time-shift invariant features, direct use of them (except for power spectrum) is impractical due to their complexity. A method for calculating the Euclidean distance in higher order spectra feature space is proposed in this paper, which avoids calculating the higher order spectra, effectively reducing the computation complexity and storage requirement. Moreover, according to the widely used scattering center model, theoretical analysis and experimental results in this paper show that the feature vector extracted from the average profile in a small target-aspect sector has better generalization performance than the average feature vector in the same sector when both of them are used as feature templates in HRRP-based RATR. The proposed Euclidean distance calculation method and average profile-based template database are applied to two classification algorithms [the template matching method (TMM) and the radial basis function network (RBFN)] to evaluate the recognition performances of higher order spectra features. Experimental results for measured data show that the power spectrum has the best recognition performance among higher order spectra.     

Identification of humans using gait

We propose a view-based approach to recognize humans from their gait. Two different image features have been considered: the width of the outer contour of the binarized silhouette of the walking person and the entire binary silhouette itself. To obtain the observation vector from the image features, we employ two different methods. In the first method, referred to as the indirect approach, the high-dimensional image feature is transformed to a lower dimensional space by generating what we call the frame to exemplar (FED) distance. The FED vector captures both structural and dynamic traits of each individual. For compact and effective gait representation and recognition, the gait information in the FED vector sequences is captured in a hidden Markov model (HMM). In the second method, referred to as the direct approach, we work with the feature vector directly (as opposed to computing the FED) and train an HMM. We estimate the HMM parameters (specifically the observation probability B) based on the distance between the exemplars and the image features. In this way, we avoid learning high-dimensional probability density functions. The statistical nature of the HMM lends overall robustness to representation and recognition. The performance of the methods is illustrated using several databases.     

基于改进的混合学习模型的手写阿拉伯数字识别方法

在特征空间维数较高的手写阿拉伯数字识别问题中,冗余的特征往往会意外增加学习模型刻画问题空间的复杂度,影响手写阿拉伯数字识别的效率和精确度。该文提出了一种基于边界对特征的敏感度值进行特征选择的支持向量机树混合学习模型,依据当前中间节点上的分类曲面对子样本空间中的样例特征的敏感程度选择特征,在新构建的子样本集上训练子节点上的支持向量机。UCI机器学习数据库中手写阿拉伯数字识别问题的仿真结果表明,与其他算法相比,该文提出的方法能够在提高或保持手写阿拉伯数字高识别精确率的同时,精简问题空间,从而简化混合学习模型的中间节点和整体结构。     

Gait recognition based on vision systems: A systematic survey

With the growing popularity of biometrics technology in the pattern recognition field, especially identification of human has gained the attention of researchers from both academia and industry. One such type of biometric technique is Gait recognition, which is used to identify a human being based on their walking style. Generally, two types of approaches are adopted by any algorithm designed for gait recognition, namely model based and model free approaches. The key reason behind the popularity of gait recognition is that it can identify a person from a considerable distance while other biometrics has failed to do so. In this paper, the authors have conducted a survey of extant studies on gait recognition in consideration of gait recognition approaches and phases of a gait cycle. Moreover, some aspects like floor sensors, accelerometer based recognition, the influences of environmental factors, which are ignored by exiting surveys, are also covered in our survey study. The information of gait is usually obtained from different parts of silhouettes. This paper also describes different benchmark datasets for gait recognition. This study will provide firsthand knowledge to the researchers working on the gait recognition domain in any real-world field. It has been observed that work done on the gait recognition with sufficiently high accuracy is limited in comparison to research on various other biometric recognition systems and has enough potential for future research.