基于像素层背景模型的复杂场景运动目标检测

为了从复杂变化背景中鲁棒地检测、提取运动目标,提出一种基于像素层背景模型的运动目标检测算法。该算法采用快速均值漂移方法将背景帧上具有相同统计特性的像素划分为一个像素层,背景模型从而被表示为一组像素层,通过与邻域像素对应的层匹配来检测运动前景像素。实验结果表明,该方法可以实时、准确地检测运动目标,特别是在摄像机颤动等原因造成的背景时域不规则变化情况下,比经典的基于混合高斯背景模型的方法具有更好的检测效果。     

Light-weight salient foreground detection for embedded smart cameras

An embedded smart camera is a stand-alone unit that not only captures images, but also includes a processor, memory and communication interface. Battery-powered, embedded smart cameras introduce many additional challenges since they have very limited resources, such as energy, processing power and memory. Computer vision algorithms running on these camera boards should be light-weight and efficient. Considering the memory requirements of an algorithm and its portability to an embedded processor should be an integral part of the algorithm design in addition to the accuracy requirements. This paper presents a light-weight and efficient background modeling and foreground detection algorithm that is highly robust against lighting variations and non-static backgrounds including scenes with swaying trees, water fountains and rain. Compared to many traditional methods, the memory requirement for the data saved for each pixel is very small in the proposed algorithm. Moreover, the number of memory accesses and instructions are adaptive, and are decreased depending on the amount of activity in the scene. Each pixel is treated differently based on its history, and instead of requiring the same number of memory accesses and instructions for every pixel, we require less instructions for stable background pixels. The plot of the number of unstable pixels at each frame also serves as a tool to find the video portions with high activity. The proposed method selectively updates the background model with an automatically adaptive rate, thus can adapt to rapid changes. As opposed to traditional methods, pixels are not always treated individually, and information about neighbors is incorporated into decision making. The results obtained with nine challenging outdoor and indoor sequences are presented, and compared with the results of different state-of-the-art background subtraction methods. The ROC curves and memory comparison of different background subtraction methods are also provided. The experimental results demonstrate the success of the proposed light-weight salient foreground detection method.     

A robust framework for joint background/foreground segmentation of complex video scenes filmed with freely moving camera

This paper explores a robust region-based general framework for discriminating between background and foreground objects within a complex video sequence. The proposed framework works under difficult conditions such as dynamic background and nominally moving camera. The originality of this work lies essentially in our use of the semantic information provided by the regions while simultaneously identifying novel objects (foreground) and non-novel ones (background). The information of background regions is exploited to make moving objects detection more efficient, and vice-versa. In fact, an initial panoramic background is modeled using region-based mosaicing in order to be sufficiently robust to noise from lighting effects and shadowing by foreground objects. After the elimination of the camera movement using motion compensation, the resulting panoramic image should essentially contain the background and the ghost-like traces of the moving objects. Then, while comparing the panoramic image of the background with the individual frames, a simple median-based background subtraction permits a rough identification of foreground objects. Joint background-foreground validation, based on region segmentation, is then used for a further examination of individual foreground pixels intended to eliminate false positives and to localize shadow effects. Thus, we first obtain a foreground mask from a slow-adapting algorithm, and then validate foreground pixels (moving visual objects + shadows) by a simple moving object model built by using both background and foreground regions. The tests realized on various well-known challenging real videos (across a variety of domains) show clearly the robustness of the suggested solution. This solution, which is relatively computationally inexpensive, can be used under difficult conditions such as dynamic background, nominally moving camera and shadows. In addition to the visual evaluation, spatial-based evaluation statistics, given hand-labeled ground truth, has been used as a performance measure of moving visual objects detection.     

Fractional Stereo Matching Using Expectation-Maximization

In our fractional stereo matching problem, a foreground object with a fractional boundary is blended with a background scene using unknown transparencies. Due to the spatially varying disparities in different layers, one foreground pixel may be blended with different background pixels in stereo images, making the color constancy commonly assumed in traditional stereo matching not hold any more. To tackle this problem, in this paper, we introduce a probabilistic framework constraining the matching of pixel colors, disparities, and alpha values in different layers, and propose an automatic optimization method to solve a maximizing a posterior (MAP) problem using expectation-maximization (EM), given only a short-baseline stereo input image pair. Our method encodes the effect of background occlusion by layer blending without requiring a special detection process. The alpha computation process in our unified framework can be regarded as a new approach by natural image matting, which handles appropriately the situation when the background color is similar to that of the foreground object. We demonstrate the efficacy of our method by experimenting with challenging stereo images and making comparisons with state-of-the-art methods.     

Background subtraction by combining Temporal and Spatio-Temporal histograms in the presence of camera movement

Background subtraction is the classical approach to differentiate moving objects in a scene from the static background when the camera is fixed. If the fixed camera assumption does not hold, a frame registration step is followed by the background subtraction. However, this registration step cannot perfectly compensate camera motion, thus errors like translations of pixels from their true registered position occur. In this paper, we overcome these errors with a simple, but effective background subtraction algorithm that combines Temporal and Spatio-Temporal approaches. The former models the temporal intensity distribution of each individual pixel. The latter classifies foreground and background pixels, taking into account the intensity distribution of each pixels’ neighborhood. The experimental results show that our algorithm outperforms the state-of-the-art systems in the presence of jitter, in spite of its simplicity.     

结合置信度加权融合与视觉注意机制的前景检测

目的 在视频前景检测中,像素级的背景减除法检测结果轮廓清晰,灵活性高。然而,基于样本一致性的像素级分类方法不能有效利用像素信息,遇到颜色伪装和出现静止前景等复杂情形时无法有效检测前景。为解决这一问题,提出一种基于置信度加权融合和视觉注意的前景检测方法。方法 通过加权融合样本的颜色置信度和纹理置信度之和判断前景,进行自适应更新样本的置信度和权值;通过划分子序列结合颜色显著性和纹理差异度构建视觉注意机制判定静止前景目标,使用更新置信度最小样本的策略保持背景模型的动态更新。结果 本文方法在CDW2014（change detection workshops 2014）和SBM-RGBD（scene background modeling red-green-blue-depth）数据集上进行检测,相较于5种主流算法,本文算法的查全率和精度相较于次好算法分别提高2.66%和1.48%,综合性能最优。结论 本文算法提高了在颜色伪装和存在静止前景等复杂情形下前景检测的精度和召回率,在公开数据集上得到更好的检测效果。可将其应用于存在颜色伪装和静止前景等复杂情形的视频监控中。     

Detecting moving objects from a video taken by a moving camera using sequential inference of background images

This paper proposes a method of detecting moving objects using sequential inference of the background in a video taken with a moving camera. In the video taken using a moving camera, all positions of pixels change every frame. The positions of the background pixels in the image frame T are not the same as the positions of the background pixels in the image frame T + 1. 2D projective transform can be used to find changes in the pixel position every frame. Bilinear interpolation with four nearest pixels around the pixel in image frame T which corresponds to a pixel in the image frame T+1 can be used for creating a background model at T + 1. Having obtained the background model, a pixel in image frame T + 1 can be determined if it is a background pixel or a foreground pixel. The detection results of the proposed method are compared with the ground truth to determine the effectiveness of the proposed method.     

自适应邻域相关性的背景建模

目的 背景建模在计算机视觉领域中是检测、跟踪、行为学习和识别的基础,被广泛地应用于视频监控的运动目标检测。混合高斯（MOG）和Codebook是其中具有代表性的方法,但它们假设像素点间信息是独立的,只保留了时域信息而忽略了空域信息,使得模型对背景的描述局限于时间上的连续性。针对上述问题,提出了一种自适应邻域相关性的背景建模方法（ANC）。方法 ANC在保留原始方法时域信息建模特性的同时,增加对邻域模型的复用,同时利用计算结果反馈自适应调整邻域区域,提高对前景值判断的准确性。首先利用原始基于像素点的背景建模方法进行候选前景检测,然后将候选前景检测结果为前景点的像素与邻域像素点模型进行对比,若邻域范围存在匹配则为背景点,若不存在则为前景点;最后引入像素置信度概念,自适应调整邻域范围的大小。结果 与MOG和Codebook相比,在changedetection标准数据库上,ANC在ROC（受试者工作特征曲线）和度量值等方面的平均精度和F-measure都提高了7%以上。结论 自适应邻域相关性的背景建模方法适用于复杂多模态背景,克服了基于像素点背景建模方法假设的局限性。与普通基于像素点的背景建模方法相比,具有更好的鲁棒性和抗噪性,对复杂背景具有更强的适应性。     

3D measures exploitation for a monocular semi-supervised fall detection system

Falls have been reported as the leading cause of injury-related visits to emergency departments and the primary etiology of accidental deaths in elderly. Thus, the development of robust home surveillance systems is of great importance. In this article, such a system is presented, which tries to address the fall detection problem through visual cues. The proposed methodology utilizes a fast, real-time background subtraction algorithm, based on motion information in the scene and pixels intensity, capable to operate properly in dynamically changing visual conditions, in order to detect the foreground object. At the same time, it exploits 3D space’s measures, through automatic camera calibration, to increase the robustness of fall detection algorithm which is based on semi-supervised learning approach. The above system uses a single monocular camera and is characterized by minimal computational cost and memory requirements that make it suitable for real-time large scale implementations.     

基于ViBe算法的改进背景减去法

ViBe背景减去算法基于RGB色彩空间对像素进行处理,在光照突然改变的情况下,会造成大面积的背景误判为运动前景;同时会将场景中的运动背景大量的误检为前景. 针对上述问题,本文提出一种结合（r,g,I）标准色彩空间的改进算法. 实验结果表明,改进算法在光照突然变化时对前景的提取具有更好的鲁棒性,同时对于场景中运动的背景像素点,取得了更好的检测效果.     

基于混合概率背景模型的视频分割方法

提出一种新的基于混合概率模型的背景建模方法,用于视频中前景物体的检测与分割。主要利用两个概率模型：隐马尔可夫模型和概率图模型建立一个混合的贝叶斯网概率模型,对视频输入中背景变化的时间和空间局部相关性(同现性)进行学习。在建立正确模型参数的基础上,贝叶斯信念传播算法根据图像输入预测当前背景状态的后验分布,并根据预测得到的背景状态对输入图像进行分割。实验结果验证了该方法的有效性和在复杂背景变化下的鲁棒性。     

Background subtraction via incremental maximum margin criterion: a discriminative subspace approach

Background subtraction is one of the basic low-level operations in video analysis. The aim is to separate static information called “background” from the moving objects called “foreground”. The background needs to be modeled and updated over time to allow robust foreground detection. Recently, reconstructive subspace learning models, such as principal component analysis (PCA) have been used to model the background by significantly reducing the data’s dimension. This approach is based on the assumption that the main information contained in the training sequence is the background meaning that the foreground has a low contribution. However, this assumption is only verified when the moving objects are either small or far away from the camera. Furthermore, the reconstructive representations strive to be as informative as possible in terms of well approximating the original data. Their objective is mainly to encompass the variability of the training data and so they give more effort to model the background in an unsupervised manner than to precisely classify pixels as foreground or background in the foreground detection. On the other hand, discriminative methods are usually less adapted to the reconstruction of data; although they are spatially and computationally much more efficient and often give better classification results compared with the reconstructive methods. Based on this fact, we propose the use of a discriminative subspace learning model called incremental maximum margin criterion (IMMC). The objective is first to enable a robust supervised initialization of the background and secondly a robust classification of pixels as background or foreground. Furthermore, IMMC also allows us an incremental update of the eigenvectors and eigenvalues. Experimental results on different datasets demonstrate the performance of this proposed approach in the presence of illumination changes.     

改进的ViBe运动目标检测算法

针对传统ViBe运动目标检测算法提取的目标存在鬼影区域、且有闪烁像素点干扰的问题,提出一种结合Surendra背景更新算法而改进的ViBe算法进行运动目标检测.利用Surendra算法快速更新背景的特点迭代得到纯净背景;对ViBe算法检测前景进行像素标记和鬼影分类判别,去除鬼影像素点和闪烁像素点;输出新的前景.实验表明:该算法可以有效地去除ViBe算法前景检测中的鬼影,并能抑制闪烁像素噪声,获取更精确的前景图像.     

基于ViBe的室外动态背景闪烁像素噪声消除方法

针对使用视觉背景提取(ViBe)模型在室外动态背景下进行移动目标检测时存在不规则闪烁像素点对前景检测结果造成干扰的问题,提出一种基于视觉背景提取算法的闪烁像素噪声消除方法。在背景模型建立阶段设定背景模型样本标准差阈值,约束背景模型的采样值范围以提高背景模型准确性。在前景检测阶段引入自适应检测阈值提高前景物体检测精度,在背景模型更新过程中对图像边缘背景像素点进行边缘抑制以阻止错误背景样本值更新到背景模型。在此基础上,结合形态学操作修复连通域,提高前景图像的完整性。最后选取多个视频序列将该方法与原始ViBe算法、形态学改进方法的检测结果进行对比。实验结果表明,该方法能有效消除闪烁像素噪声对前景检测造成的影响,获取更精确的前景图像。     

基于邻域相关性和帧间连续性的前景目标分割

提出了一种新的运动目标分割算法。首先利用像素的颜色、空间的和帧间的特性信息结合贝叶斯判别定理对视频图像进行粗分割,得到一个前景目标的二值图,由于该类方法基于像素间彼此独立的假设,导致分割出的前景目标不完整存在很多空洞。其次,基于前景目标局部邻域空间的一致性假设,计算该邻域内像素间的互相关系数;同时,基于背景的帧间连续性和前景的不连续性,计算像素帧间的互相关系数。最后,依据像素的互相关系数在该邻域内进行二次判决,以填补粗分割中前景目标内部的空洞。实验表明,在复杂背景交通视频中该分割算法具有较强的鲁棒性,并能获得更完整准确的前景目标。     

颜色和纹理特征的运动目标检测

针对复杂场景中运动目标检测这一难题,提出利用RGB颜色特征和尺度不变局部三元模式的运动目标检测算法。利用时域中值法得到估算背景图像并快速初始化背景模型。通过颜色特征、纹理特征相似性度量,融合得出背景概率网络,通过侧抑制滤波提高对比度分类出前景与背景像素,前景像素进一步进行阴影检测,将阴影点归为背景点,但不用于模型更新。将算法与GMM、SC-SOBS、SUBSENS算法在变化检测数据库中进行对比验证。实验表明,新算法在满足实时性的基础上,对动态背景,阴影和相机抖动等有一定的鲁棒性。     

Robust and efficient foreground analysis in complex surveillance videos

Mixture of Gaussians-based background subtraction (BGS) has been widely used for detecting moving objects in surveillance videos. It is very efficient and can update the background model with slow lighting changes, however, it suffers from a number of limitations in complex surveillance conditions such as quick lighting variations, heavy occlusion, foreground fragments, slow moving or stopped object etc. To address these issues, this paper first focuses on foreground analysis within the mixture of Gaussians BGS framework in long-term scene monitoring to handle (1) quick lighting changes, (2) static objects, (3) foreground fragments, (4) abandoned and removed objects, and (5) camera view changes. Then, we propose a framework with interactive mechanisms between BGS and processing from different high levels (i.e. region, frame, and tracking) to improve the accuracy of moving object detection and tracking to handle (1) objects that stop for a significant period of time and (2) slow-moving objects. The robustness and efficiency of the proposed mechanism are tested in IBM Smart Surveillance Solution on a variety of sequences, including standard datasets. The proposed method is very efficient and handles ten video streams in real-time on a 2GB Pentium IV machine with MMX optimization.     

结合加权Schatten-p范数与3D全变分的前景检测

针对低秩与稀疏方法一般将前景看作背景中存在的异常像素点，从而使得在复杂场景中前景检测精确度下降的问题，提出一种结合加权Schatten-p范数与3D全变分（3D-TV）的前景检测模型。该模型首先将观测数据三分为低秩背景、运动前景和动态干扰；然后利用3D全变分来约束运动前景，并加强对前景目标时空连续性的先验考虑，有效抑制了不连续动态背景异常点的随机扰动；最后利用加权Schatten-p范数约束视频背景的低秩性能，去除噪声干扰。实验结果表明，与鲁棒主成分分析（RPCA）、高阶RPCA（HoRPCA）和张量RPCA（TRPCA）等模型相比，所提模型的综合衡量指标F-measure值是最高的，查全率与查准率也处于最优或次优状态。由此可知，所提模型在动态背景、恶劣天气等复杂场景中能有效提高运动目标的提取精确度，且提取的前景目标视觉效果较好。     

一种基于混合概率模型的视频分割方法

该文提出一种新的基于混合概率模型视频分割方法。这个方法主要利用两个概率模型：隐马尔可夫模型和概率图模型建立一个混合的贝叶斯网概率模型,对视频输入中背景变化的时间和空间局部相关性（同现性）进行学习。在建立正确模型参数的基础上,贝叶斯信念传播算法根据图像输入预测当前背景状态的后验分布。并根据预测得到的背景状态对输入图像进行分割,实验结果显示方法的有效性和在复杂背景变化下的鲁棒性。