Incremental Tensor Subspace Learning and Its Applications to Foreground Segmentation and Tracking

Appearance modeling is very important for background modeling and object tracking. Subspace learning-based algorithms have been used to model the appearances of objects or scenes. Current vector subspace-based algorithms cannot effectively represent spatial correlations between pixel values. Current tensor subspace-based algorithms construct an offline representation of image ensembles, and current online tensor subspace learning algorithms cannot be applied to background modeling and object tracking. In this paper, we propose an online tensor subspace learning algorithm which models appearance changes by incrementally learning a tensor subspace representation through adaptively updating the sample mean and an eigenbasis for each unfolding matrix of the tensor. The proposed incremental tensor subspace learning algorithm is applied to foreground segmentation and object tracking for grayscale and color image sequences. The new background models capture the intrinsic spatiotemporal characteristics of scenes. The new tracking algorithm captures the appearance characteristics of an object during tracking and uses a particle filter to estimate the optimal object state. Experimental evaluations against state-of-the-art algorithms demonstrate the promise and effectiveness of the proposed incremental tensor subspace learning algorithm, and its applications to foreground segmentation and object tracking.     

Robust object tracking under appearance change conditions

We propose a robust visual tracking framework based on particle filter to deal with the object appearance changes due to varying illumination, pose variantions, and occlusions. We mainly improve the observation model and re-sampling process in a particle filter. We use on-line updating appearance model, affine transformation, and M-estimation to construct an adaptive observation model. On-line updating appearance model can adapt to the changes of illumination partially. Affine transformation-based similarity measurement is introduced to tackle pose variantions, and M-estimation is used to handle the occluded object in computing observation likelihood. To take advantage of the most recent observation and produce a suboptimal Gaussian proposal distribution, we incorporate Kalman filter into a particle filter to enhance the performance of the resampling process. To estimate the posterior probability density properly with lower computational complexity, we only employ a single Kalman filter to propagate Gaussian distribution. Experimental results have demonstrated the effectiveness and robustness of the proposed algorithm by tracking visual objects in the recorded video sequences.     

基于粒子滤波与稀疏表达的目标跟踪方法

针对视频序列图像目标跟踪中的光照变化问题,提出一种在粒子滤波器框架内,基于目标的局部二元模式(LBP)纹理特征,使用稀疏表达进行目标跟踪的方法。当前帧的跟踪粒子由前一帧的跟踪结果按高斯分布来生成。通过解l₁正则化最小二乘方问题,获得每个粒子对应于模板子空间的稀疏表达,确定当前帧图像中的跟踪目标。然后使用粒子滤波器生成下一帧跟踪的粒子分布。在跟踪过程中采用新的动态模板更新策略更新模板空间中的模板。实验结果证明该方法的有效性和先进性。     

基于增量式子空间学习的视觉跟踪系统

为了提高视觉跟踪方法在物体外观发生变化时的性能,提出一种基于增量式子空间学习的视觉跟踪系统。该系统利用基于增量式主成分分析的粒子滤波方法增量式地学习一个表示跟踪结果的低维特征空间,以反映目标物体的外观变化。实验结果表明,当目标物体在复杂环境中承受姿态和光照变化时,该视觉跟踪系统具有更好的性能。     

Real-time visual tracking via multi-cue based adaptive particle filter framework

Visual tracking using particle filter has been extensively investigated due to its myriad of application in the field of computer vision. However, particle filter framework performance is heavily impaired due to its inherent problems namely, particle degeneracy and impoverishment. In addition, most of the tracking methods using single cue are greatly affected by dynamic environmental challenges. To address these issues, we propose an adaptive multi-cue particle filter based real-time visual tracking framework. Three complementary cues namely, color histogram, LBP and pyramid of histogram of gradient have been exploited for object’s appearance model. These cues are integrated using the proposed adaptive fusion model for the automatic boosting of important particles and suppression of unimportant particles. Resampling method using butterfly search optimization relocate low performing particles to high likelihood area. Proposed outlier detection mechanism not only helps in detecting low performing particles but also aids in updating of the reference dictionary. Online estimation of cue reliability along with its multi-cue fusion leads to quick adaptation of the proposed tracker. On average of the outcome, our tracker achieves average center location error of 6.89 (in pixels) and average F-measure of 0.786 when evaluated on OTB-100 and VOT dataset against 13 others state-of-the-art.

     

An adaptive sample count particle filter

The particle filter technique has been used extensively over the past few years to track objects in challenging environments. Due to its nonlinear nature and the fact that it does not assume a Gaussian probability density function it tends to outperform other available tracking methods. A novel adaptive sample count particle filter (ASCPF) tracking method is presented in this paper for which the main motivation is to accurately track an object in crowded scenes using fewer particles and hence with reduced computational overhead. Instead of taking a fixed number of particles, a particle range technique is used where an upper and lower bound for the range is initially identified. Particles are made to switch between an active and inactive state within this identified range. The idea is to keep the number of active particles to a minimum and only to increase this as and when required. Active contours are also utilized to determine a precise area of support around the tracked object from which the color histograms used by the particle filter can be accurately calculated. This, together with the variable particle spread, allows a more accurate proposal distribution to be generated while using less computational resource. Experimental results show that the proposed method not only tracks the object with comparable accuracy to existing particle filter techniques but is up to five times faster.     

A hybrid occlusion free object tracking method using particle filter and modified galaxy based search meta-heuristic algorithm

An important problem in tracking methods is how to manage the changes in object appearance, such as illumination changes, partial/full occlusion, scale, and pose variation during the tracking process. In this paper, we propose an occlusion free object tracking method together with a simple adaptive appearance model. The proposed appearance model which is updated at the end of each time step includes three components: the first component consists of a fixed template of target object, the second component shows rapid changes in object appearance, and the third one maintains slow changes generated along the object path. The proposed tracking method not only can detect occlusion and handle it, but also it is robust against changes in the object appearance model. It is based on particle filter which is a robust technique in tracking and handles non-linear and non-Gaussian problems. We have also employed a meta-heuristic approach that is called Modified Galaxy based Search Algorithm (MGbSA), to reinforce finding the optimum state in the particle filter state space. The proposed method was applied to some benchmark videos and its results were satisfactory and better than results of related works.     

联合模板先验概率和稀疏表示的目标跟踪

目的 虽然基于稀疏表示的目标跟踪方法表现出了良好的跟踪效果,但仍然无法彻底解决噪声、旋转、遮挡、运动模糊、光照和姿态变化等复杂背景下的目标跟踪问题。针对遮挡、旋转、姿态变化和运动模糊问题,提出一种在粒子滤波框架内,基于稀疏表示和先验概率相结合的目标跟踪方法。方法 通过先验概率衡量目标模板的重要性,并将其引入到正则化模型中,作为模板更新的主要依据,从而获得一种新的候选目标稀疏表示模型。结果 在多个测试视频序列上,与多种流行算法相比,该算法可以达到更好的跟踪性能。在5个经典测试视频下的平均中心误差为6.77像素,平均跟踪成功率为97%,均优于其他算法。结论 实验结果表明,在各种含有遮挡、旋转、姿态变化和运动模糊的视频中,该算法可以稳定可靠地跟踪目标,适用于视频监控复杂场景下的目标跟踪。     

Multi-scale patch-based sparse appearance model for robust object tracking

When objects undergo large pose change, illumination variation or partial occlusion, most existing visual tracking algorithms tend to drift away from targets and even fail to track them. To address the issue, in this paper we propose a multi-scale patch-based appearance model with sparse representation and provide an efficient scheme involving the collaboration between multi-scale patches encoded by sparse coefficients. The key idea of our method is to model the appearance of an object by different scale patches, which are represented by sparse coefficients with different scale dictionaries. The model exploits both partial and spatial information of targets based on multi-scale patches. Afterwards, a similarity score of one candidate target is input into a particle filter framework to estimate the target state sequentially over time in visual tracking. Additionally, to decrease the visual drift caused by frequently updating model, we present a novel two-step object tracking method which exploits both the ground truth information of the target labeled in the first frame and the target obtained online with the multi-scale patch information. Experiments on some publicly available benchmarks of video sequences showed that the similarity involving complementary information can locate targets more accurately and the proposed tracker is more robust and effective than others.     

An online spatio-temporal tensor learning model for visual tracking and its applications to facial expression recognition

Robust visual tracking remains a technical challenge in real-world applications, as an object may involve many appearance variations. In existing tracking frameworks, objects in an image are often represented as vector observations, which discounts the 2-D intrinsic structure of the image. By considering an image in its actual form as a matrix, we construct the 3rd order tensor based object representation to preserve the spatial correlation within the 2-D image and fully exploit the useful temporal information. We perform incremental update of the object template using the N-mode SVD to model the appearance variations, which reduces the influence of template drifting and object occlusions. The proposed scheme efficiently learns a low-dimensional tensor representation through adaptively updating the eigenbasis of the tensor. Tensor based Bayesian inference in the particle filter framework is then utilized to realize tracking. We present the validation of the proposed tracking system by conducting the real-time facial expression recognition with video data and a live camera. Experiment evaluation on challenging benchmark image sequences undergoing appearance variations demonstrates the significance and effectiveness of the proposed algorithm.     

稀疏编码目标跟踪方法研究

针对稀疏表示用于目标跟踪时存在重构误差表示不够精确、目标模板更新错误等问题,提出一种改进的稀疏编码模型。该模型无需重构误差满足特定的先验概率分布,且加入对编码系数的自适应约束,可以取得更优的编码向量,使得跟踪结果更为准确。在此基础上,将这种改进的编码模型与粒子滤波目标跟踪算法相结合,研究并实现一种新的基于鲁棒稀疏编码模型的目标跟踪方法。该方法对每个粒子的采样区域进行编码,用所得的稀疏编码向量作为当前粒子的观测量,并采用目标模板分级更新策略,使得目标模板更加准确。实验结果表明,方法可以较好地解决目标部分遮挡和光照变化等干扰下的目标跟踪问题。     

Robust tracking with adaptive appearance learning and occlusion detection

It is still challenging to design a robust and efficient tracking algorithm in complex scenes. We propose a new object tracking algorithm with adaptive appearance learning and occlusion detection in an efficient self-tuning particle filter framework. The appearance of an object is modeled with a set of weighted and ordered submanifolds, which can guarantee the adaptability when there is fast illumination or pose change. To overcome the occlusion problem, we use the reconstruction error data of the appearance model to extract occlusion region by graph cuts. And the tracking result is improved with feedback of occlusion detection. The motion model is also integrated with adaptability to overcome the abrupt motion problem. To improve the efficiency of particle filter, the number of samples is tuned with respect to the scene conditions. Experimental results demonstrate that our algorithm can achieve great robustness, high accuracy and good efficiency in challenging scenes.     

A Competitive Neural Network for Multiple Object Tracking in Video Sequence Analysis

Tracking of moving objects in real situation is a challenging research issue, due to dynamic changes in objects or background appearance, illumination, shape and occlusions. In this paper, we deal with these difficulties by incorporating an adaptive feature weighting mechanism to the proposed growing competitive neural network for multiple objects tracking. The neural network takes advantage of the most relevant object features (information provided by the proposed adaptive feature weighting mechanism) in order to estimate the trajectories of the moving objects. The feature selection mechanism is based on a genetic algorithm, and the tracking algorithm is based on a growing competitive neural network where each unit is associated to each object in the scene. The proposed methods (object tracking and feature selection mechanism) are applied to detect the trajectories of moving vehicles in roads. Experimental results show the performance of the proposed system compared to the standard Kalman filter.     

Incremental Learning for Robust Visual Tracking

Visual tracking, in essence, deals with non-stationary image streams that change over time. While most existing algorithms are able to track objects well in controlled environments, they usually fail in the presence of significant variation of the object’s appearance or surrounding illumination. One reason for such failures is that many algorithms employ fixed appearance models of the target. Such models are trained using only appearance data available before tracking begins, which in practice limits the range of appearances that are modeled, and ignores the large volume of information (such as shape changes or specific lighting conditions) that becomes available during tracking. In this paper, we present a tracking method that incrementally learns a low-dimensional subspace representation, efficiently adapting online to changes in the appearance of the target. The model update, based on incremental algorithms for principal component analysis, includes two important features: a method for correctly updating the sample mean, and a forgetting factor to ensure less modeling power is expended fitting older observations. Both of these features contribute measurably to improving overall tracking performance. Numerous experiments demonstrate the effectiveness of the proposed tracking algorithm in indoor and outdoor environments where the target objects undergo large changes in pose, scale, and illumination.     

基于自适应表面模型的概率视频跟踪算法

提出一种鲁棒自适应表面模型，该模型中每个像素值的变化过程由一混合高斯分布描述．为了适应目标表面的变化，这些高斯参数在跟踪期间通过在线的EM算法自适应更新；在估计目标状态时。采用了粒子滤波算法。设计了基于自适应表面模型的观测模型；在处理遮挡时，采用了一种鲁棒估计技术．多组试验结果表明，该算法对光照变化、姿态变化、部分或完全遮挡下的跟踪具有较强的鲁棒性．     

一种基于核相关滤波的视觉跟踪算法

视觉跟踪是计算机视觉的一个重要方向,而核相关滤波(KCF)跟踪是视觉跟踪领域中的一种比较新颖的方法,它不同于传统基于目标特征的方法,不仅具有较高的跟踪精度,而且具有较快的跟踪速度,在实际应用中效果显著。但当物体快速运动或存在较大尺度变化等时,该方法无法准确地跟踪目标。文中提出的基于核相关滤波器的改进算法有效地解决了上述问题,其通过随机更新多模板匹配,确定了核相关滤波的学习因子,从而实现了学习因子自适应更新模型。实验结果表明,该算法根据不同的场景能快速地调整学习因子,从而提高跟踪的成功度。通过自适应学习因子和多模板匹配,该算法对部分遮挡、光照和目标尺度变化具有较强的适应性。     

基于区域协方差矩阵和2DPCA学习的视频跟踪方法研究

针对PCA在视频跟踪应用中需要将图像转换成向量而造成信息丢失和小样本等问题,提出一种基于2DPCA学习的自适应性视频跟踪方法。该方法将图像矩阵直接进行处理,保持了跟踪目标的空间结构信息。在粒子滤波框架下采用仿射变换运动模型,并通过协方差特征融合方式评估目标运动状态,提高了目标外观模型的学习能力,实现了鲁棒的自适应性跟踪效果。进行了标准的视频序列测试,结果证明提出的算法能够较好地适应目标姿态、光线和部分遮挡等跟踪问题。     

复杂背景下感兴趣运动目标的跟踪算法

针对由于复杂背景的干扰而导致不能准确跟踪感兴趣运动目标的问题,提出一种基于多特征自适应融合的粒子滤波跟踪算法。首先在HSV颜色空间中得到感兴趣运动目标的加权颜色分布模型,然后利用不变矩特征来消除背景中相似颜色物体和光照变化的干扰,两种特征通过自适应调整权重来更新粒子权值而融合于粒子滤波算法中,从而能够准确和稳定地跟踪运动目标。实验证明,该算法在运动目标平移、姿态变化、遮挡、光照变化及相似颜色干扰等复杂背景下都能够准确地进行跟踪,对背景干扰具有很强的鲁棒性。     

Object tracking based on particle filter with discriminative features

This paper presents a particle filter-based visual tracking method with online feature selection mechanism. In color-based particle filter algorithm the weights of particles do not always represent the importance correctly, this may cause that the object tracking based on particle filter converge to a local region of the object. In our proposed visual tracking method, the Bhattacharyya distance and the local discrimination between the object and background are used to define the weights of the particles, which can solve the existing local convergence problem. Experiments demonstrates that the proposed method can work well not only in single object tracking processes but also in multiple similar objects tracking processes.     

变分调整约束下的反向低秩稀疏学习目标跟踪

目的 低秩稀疏学习目标跟踪算法在目标快速运动和严重遮挡等情况下容易出现跟踪漂移现象,为此提出一种变分调整约束下的反向低秩稀疏学习目标跟踪算法。方法 采用核范数凸近似低秩约束描述候选粒子间的时域相关性,去除不相关粒子,适应目标外观变化。通过反向稀疏表示描述目标表观,用候选粒子稀疏表示目标模板,减少在线跟踪中L₁优化问题的数目,提高跟踪效率。在有界变差空间利用变分调整对稀疏系数差分建模,约束目标表观在相邻帧间具有较小变化,但允许连续帧间差异存在跳跃不连续性,以适应目标快速运动。结果 实验利用OTB（object tracking benchmark）数据集中的4组涵盖了严重遮挡、快速运动、光照和尺度变化等挑战因素的标准视频序列进行测试,定性和定量对比了本文算法与5种热点算法的跟踪效果。定性分析基于视频序列的主要挑战因素进行比较,定量分析通过中心点位置误差（central pixel error,CPE）比较跟踪算法的精度。与CNT（convolutional networks training）、SCM（sparse collaborative model）、IST（inverse sparse tracker）、DDL（discriminative dictionary learning）和LLR（locally low-rank representation）算法相比,平均CPE值分别提高了2.80、4.16、13.37、35.94和41.59。实验结果表明,本文算法达到了较高的跟踪精度,对上述挑战因素更具鲁棒性。结论 本文提出的跟踪算法,综合了低秩稀疏学习和变分优化调整的优势,在复杂场景下具有较高的跟踪精度,特别是对严重遮挡和快速运动情况的有效跟踪更具鲁棒性。