Existing methods in Person Re-Identification (ReID) often fail when simultaneously confronted with occlusions and clothing changes. In this paper, we introduce a challenging yet practical task called Occluded Cloth-Changing Re-ID (OCCRe-ID/). We propose Occlusion-aware Appearance and Shape Reasoning, the first framework OCCReID. We first propose an occlusion synthesis strategy to expose the model to real-world occlusion variations. We mitigate clothing changes by coupling silhouette-based body shape information with appearance. Unlike previous works that directly leverage unreliable features extracted from occluded images by off-the-shelf backbones, we propose an occlusion-awareness strategy to handle occlusions for ReID. An occlusion detection module is elaborately designed to generate occlusion-aware feature, which is then used to guide the framework to reason robust appearance and shape features. Extensive experiments demonstrate the superiority of our framework over both cloth-changing Re-ID and occluded Re-ID methods.

Video-based Person Re-Identification (Re-ID) is an important task in video surveillance analysis. Real-world video-based Re-ID commonly suffers from clothing changes and occlusions, which severely degenerates performance of traditional Re-ID methods. In this paper, we introduce a challenging yet practical task called Video-based Occluded Cloth-Changing Re-ID (VOCCRe-ID). To tackle occlusions, we propose an occlusion synthesis strategy to expose the model to real-world occlusion variations. To mitigate unreliable appearance caused by clothing changes, we couple body shape information from the normalized silhouette sequence. Then, we propose a cross-attention fusion mechanism to capture the complementary relationships between appearance and shape under occlusions, thus enhancing Re-ID robustness. In addition, since there are no dataset for VOCCRe-ID, we build the large-scale Occluded-VCCR dataset which explicitly presents occlusions and contains the most clothing variations. Extensive experiments show that we achieve SOTA performance over previous methods.

Person Re-Identification (Re-ID) aims at matching a person captured by a non-overlapping camera system. Real-world Re-ID presents challenges like clothing changes and occlusions, which limits the applicability of traditional appearance-based methods. Cloth-Changing Re-ID (CCRe-ID) methods that rely on cloth-invariant modalities, such as shape, gait, etc., ignore occlusions and fail to mine the complementary relationship across modalities. Meanwhile, methods that explicitly focus on occlusion management struggle with cloth-changing scenarios. To address these, we propose ACML: Attention-based Cross-Modality Learning, the first framework to tackle both clothing changes and occlusion in Re-ID. Our lightweight framework comprises a unified network with cascaded Cross-Attention Blocks that extracts appearance and shape features collaboratively, enhancing robustness under clothing changes, viewpoint variations, and poor illumination conditions. Inputs to the network are produced by our novel occlusion synthesis module, which not only helps exposing the model to occlusions but also guides the model to adaptively attend to informative cues and reduce noise. Experiments demonstrate the effectiveness of ACML on both CCRe-ID and occluded Re-ID datasets.

Traditional approaches for Person Re-identification (ReID) rely heavily on modeling the appearance of persons. This measure is unreliable over longer durations due to the possibility for changes in clothing or biometric information. Furthermore, viewpoint changes significantly degrade the matching ability of these methods. In this paper, we propose "Contrastive Viewpoint-aware Shape Learning for Long-term Person Re-Identification" (CVSL) to address these challenges. Our method robustly extracts local and global texture-invariant human body shape cues from 2D pose using the Relational Shape Embedding branch, which consists of a pose estimator and a shape encoder built on a Graph Attention Network. To enhance the discriminability of the shape and appearance of identities under viewpoint variations, we propose Contrastive Viewpoint-aware Losses (CVL). CVL leverages contrastive learning to simultaneously minimize the intra-class gap under different viewpoints and maximize the inter-class gap under the same viewpoint. Extensive experiments demonstrate that our proposed framework outperforms state-of-the-art methods on long-term person Re-ID benchmarks.

Image classification is a fundamental task in computer vision. A variety of deep learning models based on the Convolutional Neural Network (CNN) architecture have proven to be an efficient solution. Numerous improvements have been proposed over the years, where broader, deeper, and denser networks have been constructed. However, the atomic operation for these models has remained a linear unit (single neuron). In this work, we pursue an alternative dimension by hypothesizing the atomic operation to be performed by a quadratic unit. We construct convolutional layers using quadratic neurons for feature extraction and subsequently use dense layers for classification. We perform analysis to quantify the implication of replacing linear neurons with quadratic units. Results show a keen improvement in classification accuracy with quadratic neurons over linear neurons.

An unauthorized or an accidental change in the view of a surveillance camera is called a tampering. Algorithms that detect tampering by analyzing the video are referred to as camera tampering detection algorithms. Most evaluations on camera tampering detection methods are presented based on individually collected datasets. One of the major challenges in the area of camera tamper detection is the absence of a public dataset with sufficient size and variations for an extensive performance evaluation. We propose a large scale synthetic dataset called University of Houston Camera Tampering Detection dataset (UHCTD) for development and testing of camera tampering detection methods. The dataset consists of a total 576 tampers with over 288 hours of video captured from two surveillance cameras. To establish an initial benchmark, we cast camera tampering detection as a classification problem. We train and evaluate three different deep architectures that have shown promise in scene classification, Alexnet, Resnet, and Densenet. Results are presented to show how the dataset can be used to train and classify images as normal, and tampered within and across cameras.

Camera tamper detection is the ability to detect faults and operational failures in video surveillance cameras by analyzing the video. Researchers have increasingly focused on such techniques attributing to the ubiquitous deployment of large scale surveillance systems. In this paper, a signal detection theory approach is proposed to quantitatively analyze the information being captured by the camera and to detect tampers. Signal activity is used as a feature to measure the amount of information in the image. The distribution of features representing the normal operation of a camera are modeled as a Gaussian mixture model (GMM). The GMM is trained using synthetic data. To reduce the effects of noise, a Kalman filter is used to model changes in signal activity in the video. Experimental results show that the proposed approach out performed the state-of-the-art [13] in detecting tampered images with higher accuracy while generating lower false alarms.