基于在线判别式字典学习的鲁棒视觉跟踪

现有子空间跟踪方法较好地解决了目标表观变化和遮挡问题,但是它对复杂背景下目标跟踪的鲁棒性较差。针对此问题,该文首先提出一种基于Fisher准则的在线判别式字典学习模型,利用块坐标下降和替换操作设计了该模型的在线学习算法用于视觉跟踪模板更新。其次,定义候选目标编码系数与目标样本编码系数均值之间的距离为系数误差,提出以候选目标的重构误差与系数误差的组合作为粒子滤波的观测似然跟踪目标。实验结果表明:与现有跟踪方法相比,该文跟踪方法具有较强的鲁棒性和较高的跟踪精度。     

基于置信区域内多级动态层表达的类贯序蒙特卡洛视觉跟踪方法

视觉跟踪是智能监控、机器人和视觉导航等领域的核心技术.针对现有类贯序蒙特卡洛跟踪方法复杂度高、实时性差的问题,本文提出了一种融合置信区域内多级动态层表达的跟踪方法,采用更加可靠、有效的粒子模拟状态后验概率.该方法利用检测模块得到目标可能出现的置信区域,根据真实目标尺寸给出一种粒子采样策略,每个粒子代表一级动态层表达,并为每个粒子建立双层运动模型;构建Mean-Shift分块观测模型以引入空间和外观信息,同时根据子块的匹配程度计算粒子权值、检测目标遮挡状态并提出模型更新策略.在公开视频序列上同经典粒子滤波和Mean-Shift等算法的实验对比结果证明了本文算法具有较优的跟踪准确度和实时性.     

采用多特征融合的子块自动提取方法

基于可变形模型的目标跟踪算法因其能够处理目标部分遮挡及形变问题成为目标跟踪领域的研究热点。当目标发生形变或部分遮挡时,可变形模型跟踪器可利用未被遮挡的子块继续完成跟踪。现有基于子块的目标跟踪算法均为手动选取子块的个数和尺寸,但在实际应用中,很难为子块的选取提供人机交互的机会,且手动选取子块易受主观因素影响。针对上述情况,提出了一种采用多特征融合的子块自动提取方法,该方法首先采用基于人眼视觉注意机制对目标模板的显著性区域进行度量;其次,利用边缘方向离散度对目标的纹理丰富度进行度量;然后,融合上述特征获得联合适配性置信度,并根据目标的面积和宽高比自适应确定子块的个数和尺寸;最后,根据联合适配性置信度提取目标子块。实验结果表明,与现有手动选取子块的可变形模型目标跟踪方法相比,采用所提方法自动提取的子块可获得更高的跟踪精度。     

基于多表观特征子模型更新的鲁棒视觉跟踪

在视觉跟踪中,传统模型更新算法在遮挡、光照变化及自身旋转等情况下通常存在鲁棒性较差的问题.为改善该性能,提出一种对多表观特征相应子模型进行选择性更新的鲁棒视觉跟踪算法.该算法首先建立候选子模型库,然后通过三个互补特征融合的粒子滤波跟踪确定当前帧目标位置和信息,最后将当前帧三种特征直方图信息与候选库中各子模型分别计算加权相似度,更新候选库后与阈值比较,判断是否更新当前子模型.实验结果表明：本文算法能够对特征相应子模型进行有效的选择性更新,与对比算法比较,在多种复杂变化的跟踪条件下,总体上能够具有更好的跟踪鲁棒性.     

一种新型多特征融合粒子滤波视觉跟踪算法

针对单一视觉信息在动态变化环境下描述目标不够充分、跟踪目标不够稳定的缺点,提出了一种基于粒子滤波框架的新型多特征融合的视觉跟踪算法。采用颜色和形状信息来描述运动模型,通过民主合成策略将两种信息融合在一起,使得跟踪算法能根据当前跟踪形势自适应调整两种信息的权重以期达到最佳的最大似然比,实现信息间的优势互补。在设计粒子滤波跟踪算法时,利用自适应信息融合策略构建似然模型,提高了粒子滤波跟踪算法在复杂场景下的稳健性。实验结果表明,多特征融合跟踪算法不仅能准确、高效地跟踪目标,而且对光照、姿态变化引起的目标表观变化具有良好的鲁棒性。     

在线鲁棒判别式字典学习视觉跟踪

传统子空间跟踪较好解决了目标表观变化和遮挡问题,但其仍存在对复杂背景下目标跟踪鲁棒性不足和模型漂移等问题.针对这两个问题,本文首先通过增大背景样本的重构误差和利用L1范数损失函数建立一种在线鲁棒判别式字典学习模型;其次,利用块坐标下降设计了该模型的在线学习算法用于视觉跟踪模板更新;最后,以粒子滤波为框架,结合提出的模板更新方法实现了鲁棒的视觉跟踪.实验结果表明:与IVT(Incremental Visual Tracking)、L1APG(L1-tracker using Accelerated Proximal Gradient)、ONNDL(Online Non-Negative Dictionary Learning)和PCOM(Probability Continuous Outlier Model)等典型跟踪方法相比,本文方法具有较强的鲁棒性和较高的跟踪精度.     

自适应转移概率交互式多模型跟踪算法

针对标准的交互式多模型算法（Interacting Multiple Model,IMM）存在模型集设计困难和采用固定转移概率矩阵导致模型切换缓慢、跟踪精度下降的不足,提出一种自适应转移概率IMM算法.首先,提出了一种新的模型集设计方法,将强跟踪修正输入估计（Strong Tracking Modified Input Estimation,STMIE）模型和匀速运动（Constant Velocity,CV）模型作为IMM算法的模型集,利用STMIE算法对高机动目标的跟踪能力以及CV模型对非机动目标跟踪的高精度,实现对目标的全面自适应跟踪.其次,提出一种依据模型似然函数值对Markov转移概率进行实时修正的方法,增强匹配模型的作用,削弱不匹配模型的影响.仿真结果表明,依据模型似然函数修正转移概率的方法使IMM算法的模型切换速度和跟踪精度都得到提高,提出的IMM-STMIECV算法的跟踪精度高于IMM-CVCA、IMM-CVCACT以及IMM-CVCS算法.     

基于模型互更新的多模图像融合跟踪算法

针对复杂环境下引起的目标失跟问题,提出了一种基于模型互更新的可见光与红外图像融合跟踪算法。基于把视觉跟踪问题视为"中心-周围"分类的思想,首先从可见光与红外图像中分别提取目标及周围像素点的特征,然后采用Boosting算法训练得到跟踪模型。基于分类结果计算像素点的置信度,采用决策级融合方法得到似然图像,通过均值漂移算法估计目标位置。最后在Co-Training框架下结合目标跟踪结果进行模型的互更新。实验结果表明,该算法提高了跟踪的鲁棒性,有效利用了多模图像的信息。     

基于局部分块学习的在线视觉跟踪

视觉跟踪中,如何构建一种能够适应目标表观特征变化的目标模型是增强算法跟踪精度和稳定性的关键之一。本文提出利用跟踪区域内像素的初始分类标记来构建目标的局部分块模型,并在贝叶斯理论框架下提出了基于局部分块学习的在线视觉跟踪算法。首先,利用标定的初始跟踪区域构建目标的局部分块模型;然后,在当前跟踪区域中通过局部分块学习和贝叶斯估计确定当前帧的跟踪结果;最后,利用特征聚类对局部分块模型进行更新。实验结果表明：所提算法对目标表观变化的适应性明显增强,跟踪精度和稳定性较近年来的同类算法均有一定提高。     

基于自适应观测模型交互多模型粒子滤波的红外机动目标跟踪

针对红外目标跟踪问题,提出一种混合观测模型以描述日标像素灰度的渐变以及目标的突然消失或复现,采用在线EM算法对观测模型参数进行更新;将自适应观测模型与交互多模型粒子滤波相结合用于目标跟踪;基于概率排斥原则改进了似然函数,将上述算法推广到多目标跟踪领域.单目标和多目标跟踪仿真结果验证了所提算法的有效性.     

Collaborative object tracking model with local sparse representation

There existed many visual tracking methods that are based on sparse representation model, most of them were either generative or discriminative, which made object tracking more difficult when objects have undergone large pose change, illumination variation or partial occlusion. To address this issue, in this paper we propose a collaborative object tracking model with local sparse representation. The key idea of our method is to develop a local sparse representation-based discriminative model (SRDM) and a local sparse representation-based generative model (SRGM). In the SRDM module, the appearance of a target is modeled by local sparse codes that can be formed as training data for a linear classifier to discriminate the target from the background. In the SRGM module, the appearance of the target is represented by sparse coding histogram and a sparse coding-based similarity measure is applied to compute the distance between histograms of a target candidate and the target template. Finally, a collaborative similarity measure is proposed for measuring the difference of the two models, and then the corresponding likelihood of the target candidates is input into a particle filter framework to estimate the target state sequentially over time in visual tracking. Experiments on some publicly available benchmarks of video sequences showed that our proposed tracker is robust and effective.     

改进的协同训练框架下压缩跟踪

针对基于传统协同训练框架的视觉跟踪算法在复杂环境下鲁棒性不足,该文提出一种改进的协同训练框架下压缩跟踪算法。首先,利用空间布局信息,基于能量熵最大化的在线特征选择技术提升压缩感知分类器的判别能力,分别在灰度空间和局部二值模式空间建立起基于结构压缩特征的两个独立分类器。然后,基于候选样本信任度分布熵的分类器联合机制实现互补性特征的自适应融合,增强跟踪结果的鲁棒性。最后,在级联的梯度直方图分类器辅助下,通过具备样本选择能力的新型协同训练准则完成联合外观模型的准确更新,解决了协同训练误差的积累问题。对大量具有挑战性的序列的对比实验结果验证了该算法相比于其它近似跟踪算法具有更优的性能。     

一种视觉跟踪中的模板更新策略

针对复杂场景中的目标外观和背景变化引起的模板 更新问题, 提出了一种新的视觉跟踪模板更新策略,用以提高目标模板正确性。算法利用特征信息在 时间和空间上的区别和变化,进行特征子量分类更新,避免了模型过更新,提高了目标模型 的容错能力,使更新带来的误差尽量小,以适应目标和背景信息的不断变化,在一定程度上 提高了跟踪算法的精准度和鲁棒性。实验结果表明,本文方法在视频跟踪系统中具有优越的 性 能,可以在目标运动、变化和遮挡情况下实现鲁棒跟踪。     

Discriminative metric preservation for tracking low-resolution targets

Tracking low-resolution (LR) targets is a practical yet quite challenging problem in real video analysis applications. Lack of discriminative details in the visual appearance of the LR target leads to the matching ambiguity, which confronts most existing tracking methods. Although artificially enhancing the video resolution by superresolution (SR) techniques before analyzing might be an option, the high demand of computational cost can hardly meet the requirements of the tracking scenario. This paper presents a novel solution to track LR targets without explicitly performing SR. This new approach is based on discriminative metric preservation that preserves the data affinity structure in the high-resolution (HR) feature space for effective and efficient matching of LR images. In addition, we substantialize this new approach in a solid case study of differential tracking under metric preservation and derive a closed-form solution to motion estimation for LR video. In addition, this paper extends the basic linear metric preservation method to a more powerful nonlinear kernel metric preservation method. Such a solution to LR target tracking is discriminative, robust, and efficient. Extensive experiments validate the entrustments and effectiveness of the proposed approach and demonstrate the improved performance of the proposed method in tracking LR targets.     

Online semi-supervised compressive coding for robust visual tracking

In this paper we propose an online semi-supervised compressive coding algorithm, termed SCC, for robust visual tracking. The first contribution of this work is a novel adaptive compressive sensing based appearance model, which adopts the weighted random projection to exploit both local and discriminative information of the object. The second contribution is a semi-supervised coding technique for online sample labeling, which iteratively updates the distributions of positive and negative samples during tracking. Under such a circumstance, the pseudo-labels of unlabeled samples from the current frame are predicted according to the local smoothness regularizer and the similarity between the prior and the current model. To effectively track the object, a discriminative classifier is online updated by using the unlabeled samples with pseudo-labels in the weighted compressed domain. Experimental results demonstrate that our proposed algorithm outperforms the state-of-the-art tracking methods on challenging video sequences.     

Object tracking using discriminative sparse appearance model

Object tracking based on sparse representation formulates tracking as searching the candidate with minimal reconstruction error in target template subspace. The key problem lies in modeling the target robustly to vary appearances. The appearance model in most sparsity-based trackers has two main problems. The first is that global structural information and local features are insufficiently combined because the appearance is modeled separately by holistic and local sparse representations. The second problem is that the discriminative information between the target and the background is not fully utilized because the background is rarely considered in modeling. In this study, we develop a robust visual tracking algorithm by modeling the target as a model for discriminative sparse appearance. A discriminative dictionary is trained from the local target patches and the background. The patches display the local features while their position distribution implies the global structure of the target. Thus, the learned dictionary can fully represent the target. The incorporation of the background into dictionary learning also enhances its discriminative capability. Upon modeling the target as a sparse coding histogram based on this learned dictionary, our tracker is embedded into a Bayesian state inference framework to locate a target. We also present a model update scheme in which the update rate is adjusted automatically. In conjunction with the update strategy, the proposed tracker can handle occlusion and alleviate drifting. Comparative results on challenging benchmark image sequences show that the tracking method performs favorably against several state-of-the-art algorithms.     

Visual object tracking via online sparse instance learning

Sparse representation has been attracting much more attention in visual tracking. However most sparse representation based trackers only focus on how to model the target appearance and do not consider the learning of sparse representation when the training samples are imprecise, and hence may drift or fail in the challenging scene. In this paper, we present a novel online tracking algorithm. The tracker integrates the online multiple instance learning into the recent sparse representation scheme. For tracking, the integrated sparse representation combining texture, intensity and local spatial information is proposed to model the target. This representation takes both occlusion and appearance change into account. Then, an efficient online learning approach is proposed to select the most distinguishable features to separate the target from the background samples. In addition, the sparse representation is dynamically updated online with respect to the current context. Both qualitative and quantitative evaluations on challenging benchmark video sequences demonstrate that the proposed tracking algorithm performs favorably against several state-of-the-art methods.     

结合GLCM与三阶张量建模的在线目标跟踪

为提高目标跟踪算法对多种目标表观变化场景的自适应能力和跟踪精度,论文提出一种结合灰度共生(GLCM)与三阶张量建模的目标优化跟踪算法。该算法首先提取目标区域的灰度信息,通过GLCM的高区分度特征对目标进行二元超分描述,并结合三阶张量理论融合目标区域的多视图信息,建立起目标的三阶张量表观模型。然后利用线性空间理论对表观模型进行双线性展开,通过在线模型特征值描述与双线性空间的增量特征更新,明显降低模型更新时的运算量。跟踪环节,建立二级联合跟踪机制,结合当前时刻信息通过在线权重估计构建动态观测模型,以真实目标视图为基准建立静态观测模型对跟踪估计动态调整,以避免误差累积出现跟踪漂移,最终实现对目标的稳定跟踪。通过与典型算法进行多场景试验对比,表明该算法能够有效应对多种复杂场景下的运动目标跟踪,平均跟踪误差均小于9像素。     

基于主分量寻踪的鲁棒视觉跟踪

传统子空间跟踪易受到模型漂移的影响而导致跟踪失败.针对此问题,本文提出一种基于主分量寻踪的鲁棒视觉跟踪方法.该方法以多个模板张成的子空间作为目标表观模型,利用主分量寻踪求解候选目标的误差分量,在粒子滤波框架下利用候选目标的误差分量估计最优状态参数.为了适应目标表观变化并克服模型漂移,本文提出一种模板更新方法.当跟踪结果与目标模板相似时,该方法利用跟踪结果更新目标模板,否则利用跟踪结果的低秩分量更新目标模板.在多个具有挑战性的图像序列上的实验结果表明:与现有跟踪方法相比,文中的跟踪方法具有较优的跟踪性能.