Spatially constrained level-set tracking and segmentation of non-rigid objects

Level-set is a widely used technique in segmentation-based tracking due to its flexibility in handling 2D topological changes and computational efficiency. Most existing level-set models aim at grouping pixels that have similar features into a region, without consideration of the spatial relationship of these pixels. In this paper, we present a novel level-set tracking method that incorporates spatial information to improve the robustness and accuracy of tracking non-rigid objects. Both tracking and segmentation are performed in a unified probabilistic framework, with additional spatial constraints from a part-based model—the Hough Forests. In the stage of tracking, the rigid motion of the target object is estimated by rigid registration in both the color space and the Hough voting space. Then in the stage of segmentation, some support points are obtained from back-projection, and guide the level-set evolution to capture the shape deformation. We conduct quantitative evaluation on two recently proposed public benchmarks: a non-rigid object tracking dataset and the CVPR2013 online tracking benchmark, involving 61 sequences in total. The experimental results demonstrate that our tracking method performs comparably to the state-of-the-arts in the CVPR2013 benchmark, while shows significantly improved performance in tracking non-rigid objects.     

目标遮挡情况下的压缩跟踪算法

针对经典压缩跟踪算法在目标被遮挡时容易导致目标丢失的问题,提出了一种基于目标遮挡情况下的压缩跟踪算法.该方法首先依据分类器的最大响应值判断目标是否被遮挡.若发生遮挡则利用基于颜色直方图特征的粒子滤波算法进行跟踪预测,即将遮挡前提取的目标颜色直方图与粒子的颜色直方图进行相似性比较.为确保目标再现时能及时准确地捕捉其位置,再利用Harris角点特征进一步验证,并将预测的位置作为目标位置继续压缩跟踪.仿真结果表明,该算法能够准确地判断遮挡的发生,平均跟踪成功率较经典的压缩跟踪算法提高了24%,有效提高了跟踪的鲁棒性.     

Performance measures for video object segmentation and tracking

We propose measures to evaluate quantitatively the performance of video object segmentation and tracking methods without ground-truth (GT) segmentation maps. The proposed measures are based on spatial differences of color and motion along the boundary of the estimated video object plane and temporal differences between the color histogram of the current object plane and its predecessors. They can be used to localize (spatially and/or temporally) regions where segmentation results are good or bad; and/or they can be combined to yield a single numerical measure to indicate the goodness of the boundary segmentation and tracking results over a sequence. The validity of the proposed performance measures without GT have been demonstrated by canonical correlation analysis with another set of measures with GT on a set of sequences (where GT information is available). Experimental results are presented to evaluate the segmentation maps obtained from various sequences using different segmentation approaches.     

Automatic video segmentation and tracking for content-based applications

Advanced multimedia applications have to provide content-related functionalities such as search and retrieval of meaningful objects, detection and analysis of events, and understanding of scenes, which allow the user to access and manipulate the multimedia content with greater flexibility. This greatly depends on automatic techniques for extracting such objects from multimedia data. In this article we intend to provide a tutorial on the state-of-the-art in video segmentation and tracking technology with particular attention paid to the recent developments in attention-based object extraction. Performance results are included to highlight this emerging technology     

基于改进的混合高斯模型的运动目标跟踪研究

对传统混合高斯背景模型作了改进,消除了缓慢运动目标对背景模型的影响,其中提出了目标间差分方法区分出前后帧变化区,对不同区域采用不同的学习权重更新策略。通过实验证明,该改进算法提高了背景模型的健壮性,在跟踪系统中获得较好效果。     

Segmentation and tracking of moving objects for content-based videocoding

To enable content-based functionalities in video coding, a decomposition of the scene into physical objects is required. Such objects are normally not characterised by homogeneous colour, intensity, or optical flow. Therefore, conventional techniques based on these low-level features cannot perform the desired segmentation. The authors address segmentation and tracking of moving objects and present a new video object plane (VOP) segmentation algorithm that extracts semantically meaningful objects. A morphological motion filter detects physical objects by identifying areas that are moving differently from the background. A new filter criterion is introduced that measures the deviation of the estimated local motion from the synthesised global motion. A two-dimensional binary model is derived for the object of interest and tracked throughout the sequence by a Hausdorff object tracker. To accommodate for rotations and changes in shape, the model is updated every frame by a two-stage method that accounts for rigid and non-rigid moving parts of the object. The binary model then guides the actual VOP extraction, whereby a novel boundary post-processor ensures high boundary accuracy. Experimental results demonstrate the performance of the proposed algorithm     

Heuristic algorithm for visual tracking of deformable objects

Many vision problems require fast and accurate tracking of objects in dynamic scenes. These problems can be formulated as exploration problems and thus can be expressed as a search into a state space based approach. However, these problems are hard to solve because they involve search through a space of transformations corresponding to all the possible motion and deformation. In this paper, we propose a heuristic algorithm through the space of transformations for computing target 2D motion. Three features are combined in order to compute efficient motion: (1) a quality of function match based on a holistic similarity measurement, (2) Kullback–Leibler measure as heuristic to guide the search process and (3) incorporation of target dynamics into the search process for computing the most promising search alternatives. Once 2D motion has been calculated, the result value of the quality of function match computed is used with the purpose of verifying template updates. A template will be updated only when the target object has evolved to a transformed shape dissimilar with respect to the actual shape. Also, a short-term memory subsystem is included with the purpose of recovering previous views of the target object. The paper includes experimental evaluations with video streams that illustrate the efficiency and suitability for real-time vision based tasks in unrestricted environments.     

Real-time vessel segmentation and tracking for ultrasound imaging applications

A method for vessel segmentation and tracking in ultrasound images using Kalman filters is presented. A modified Star-Kalman algorithm is used to determine vessel contours and ellipse parameters using an extended Kalman filter with an elliptical model. The parameters can be used to easily calculate the transverse vessel area which is of clinical use. A temporal Kalman filter is used for tracking the vessel center over several frames, using location measurements from a handheld sensorized ultrasound probe. The segmentation and tracking have been implemented in real-time and validated using simulated ultrasound data with known features and real data, for which expert segmentation was performed. Results indicate that mean errors between segmented contours and expert tracings are on the order of 1%-2% of the maximum feature dimension, and that the transverse cross-sectional vessel area as computed from estimated ellipse parameters a, b as determined by our algorithm is within 10% of that determined by experts. The location of the vessel center was tracked accurately for a range of speeds from 1.4 to 11.2 mm/s.     

一种简单易行的运动对象分割方法

在兼顾运动图像分割效果和实时性的原则上,提出了一种简单有效的分割方法。首先利用二次帧差的方法求出图像帧的运动区域,去除结果中不准确的小区域,最后利用二次扫描的方法填充该区域。实验证明：利用该方法得到了较好的分割效果并节省了处理时间。     

Computational sensor for visual tracking with attention

This paper presents a VLSI embodiment of an optical tracking computational sensor which focuses attention on a salient target in its field of view. Using both low-latency massive parallel processing and top-down sensory adaptation, the sensor suppresses interference front features irrelevant for the task at hand, and tracks a target of interest at speeds of up to 7000 pixels/s. The sensor locks onto the target to continuously provide control for the execution of a perceptually guided activity. The sensor prototype, a 24×24 array of cells, is built in 2-μm CMOS technology. Each cell occupies 62 μm×62 μm of silicon, and contains a photodetector and processing electronics     

Improved tracking of limb occlusion pressure for surgicaltourniquets

Constant-pressure tourniquets are widely used to occlude blood flow into a patient's limb to facilitate the performance of a wide variety of surgical procedures. Adaptive tourniquets that automatically adjust the cuff pressure to the minimum necessary for occlusion (limb occlusion pressure) as a function of the patient's changing systolic blood pressure are expected to reduce the incidence of tourniquet-related injuries. However, these devices have not been widely used, largely due to problems in tracking the systolic blood pressure safely, accurately, and reliably in clinical environments with noise present. Initial lab trials and clinical trials compared the performance in tracking limb occlusion pressure during varying noise conditions of a typical oscillometric blood pressure monitor with that of a prototype system. The prototype system functions by detecting noise and rapidly estimating limb occlusion pressure using only data uncorrupted by noise. Results showed that the prototype consistently estimated limb occlusion pressure more rapidly, more accurately, and more reliably than the oscillometric monitor in noisy conditions typical of surgical procedures. The results also indicate that the prototype is feasible for incorporation into an adaptive tourniquet     

A fast valley-based segmentation for detection of slowly moving objects

Moving object detection in a video sequence is the first and most important step in many computer vision applications. However, it is challenging for a machine to match with the human visual perception level. Motion information of slowly moving object is highly erroneous in comparison with fast moving object. Therefore, in real time, accurate segmentation of slowly moving objects is more challenging. In this paper, a fast and efficient segmentation algorithm is proposed for the detection of slowly moving object in a video sequence. The proposed method has three steps to extract the slowly moving object in a video. In the first step, an averaging frame difference method is proposed to extract the motion information. In the second step, a valley-based thresholding is proposed to segment all the frames of a video. In the final step, the motion information and spatial homogeneous region information are merged to extract the slowly moving object.     

A hybrid algorithm for automatic segmentation of slowly moving objects

Segmentation of moving objects in video sequences is a basic task in many applications. However, it is still challenging due to the semantic gap between the low-level visual features and the high-level human interpretation of video semantics. Compared with segmentation of fast moving objects, accurate and perceptually consistent segmentation of slowly moving objects is more difficult. In this paper, a novel hybrid algorithm is proposed for segmentation of slowly moving objects in video sequence aiming to acquire perceptually consistent results. Firstly, the temporal information of the differences among multiple frames is employed to detect initial moving regions. Then, the Gaussian mixture model (GMM) is employed and an improved expectation maximization (EM) algorithm is introduced to segment a spatial image into homogeneous regions. Finally, the results of motion detection and spatial segmentation are fused to extract final moving objects. Experiments are conducted and provide convincing results.     

基于目标匹配的视频对象跟踪算法

视频对象分割算法的性能好坏将直接影响MPEG-4编码产品的质量。连续两次差分后自适应处理，对差分图像取交集获得运动对象的边界，形态学处理后获得二值分割掩模进而提取运动目标。基于改进的Hausdorff距离度量法对后续帧中视频对象进行跟踪。实验结果证明，该方法能够从背景不变的图像序列中较好的提取出运动对象，具有较强的鲁棒性。     

Electromagnetic imaging for complex cylindrical objects

Electronic imaging of complex cylindrical objects with arbitrary cross sections was investigated, assuming an incident wave upon both penetrable inhomogeneous dielectric cylinders and perfectly conducting cylinders with known shape, and external measurements of the scanned field. By properly processing the scattered held measurements, the dielectric permittivity distribution of the scanned object can be reconstructed. A theoretical formulation was based on proper arrangement of the incident field directions resulting in a set of integral equations derived and solved by the moment method and the unrelated illumination method. Numerical results demonstrate the capability of the imaging algorithm. Good reconstruction results were obtained even in the presence of additive random noise. In addition, noise effects on the reconstruction results were investigated.     

Improved mean shift algorithm for occlusion pedestrian tracking

Occlusion pedestrian tracking is still a difficult problem in video surveillance, while traditional mean shift tracking algorithms fail to track these kinds of targets. Proposed is an improved mean shift tracking approach to solve this problem. Two aspects are improved for the traditional mean shift tracking algorithm. First, occlusion layers are used to represent pedestrian occlusion relation and the non-occlusion part of each pedestrian which is obtained according to occlusion relation is used for the mean shift tracking algorithm. Secondly, the states of the related occlusion pedestrians are gradually adjusted one by one to eliminate the occlusion effect, during the tracking process. The contrast experiment results show that the improved algorithm is real time for well tracking the occlusion pedestrians which cannot be tracked by the traditional mean shift tracking algorithm.     

面向图像语义分割任务的多级注意力蒸馏学习

传统的蒸馏学习仅通过大网络对轻量网络进行单向蒸馏,不但难以从轻量网络的学习状态中得到反馈信息,对训练过程进行优化调整,同时还会限制轻量网络的特征表达能力.本文提出结合自身多级注意力上下文信息进行自我学习优化的方法(MAD,Multi Attention Distillation),以自监督的方式使自身成熟的部分约束不成...     

Video object segmentation and tracking using region-based statistics

Two new region-based methods for video object tracking using active contours are presented. The first method is based on the assumption that the color histogram of the tracked object is nearly stationary from frame to frame. The proposed method is based on minimizing the color histogram difference between the estimated objects at a reference frame and the current frame using a dynamic programming framework. The second method is defined for scenes where there is an out-of-focus blur difference between the object of interest and the background. In such scenes, the proposed “defocus energy” can be utilized for automatic segmentation of the object boundary, and it can be combined with the histogram method to track the object more efficiently. Experiments demonstrate that the proposed methods are successful in difficult scenes with significant background clutter.     

Localisation and tracking of multiple unknown objects in realenvironments

The Letter presents a real-time surveillance system able to localise and track multiple unknown objects (e.g. trunks, trash compactors, etc.) moving simultaneously in a sanitary landfill. Elementary features of moving image areas are used for object localisation, and a network of extended Kalman filters is applied for multiple object tracking