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1. MBW: Multi-view Bootstrapping in the Wild

   Mosam Dabhi ; Chaoyang Wang ; Tim Clifford ; László Jeni ; Ian Fasel ; Simon Lucey ( November 2022 , Advances in neural information processing systems)

   S. Koyejo ; S. Mohamed ; A. Agarwal ; D. Belgrave ; K. Cho ; A. Oh (Ed.)

   Labeling articulated objects in unconstrained settings has a wide variety of applications including entertainment, neuroscience, psychology, ethology, and many fields of medicine. Large offline labeled datasets do not exist for all but the most common articulated object categories (e.g., humans). Hand labeling these landmarks within a video sequence is a laborious task. Learned landmark detectors can help, but can be error-prone when trained from only a few examples. Multi-camera systems that train fine-grained detectors have shown significant promise in detecting such errors, allowing for self-supervised solutions that only need a small percentage of the video sequence to be hand-labeled. The approach, however, is based on calibrated cameras and rigid geometry, making it expensive, difficult to manage, and impractical in real-world scenarios. In this paper, we address these bottlenecks by combining a non-rigid 3D neural prior with deep flow to obtain high-fidelity landmark estimates from videos with only two or three uncalibrated, handheld cameras. With just a few annotations (representing 1−2 % of the frames), we are able to produce 2D results comparable to state-of-the-art fully supervised methods, along with 3D reconstructions that are impossible with other existing approaches. Our Multi-view Bootstrapping in the Wild (MBW) approach demonstrates impressive results on standard human datasets, as well as tigers, cheetahs, fish, colobus monkeys, chimpanzees, and flamingos from videos captured casually in a zoo. We release the codebase for MBW as well as this challenging zoo dataset consisting of image frames of tail-end distribution categories with their corresponding 2D and 3D labels generated from minimal human intervention. 

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2. Toward Automated Classroom Observation: Predicting Positive and Negative Climate

   https://doi.org/10.1109/FG.2019.8756529  

   Ramakrishnan, Anand ; Ottmar, Erin ; LoCasale-Crouch, Jennifer ; Whitehill, Jacob ( May 2019 , Automatic Face and Gesture Recognition)

   We devised and evaluated a multi-modal machine learning-based system to analyze videos of school classrooms for "positive climate" and "negative climate", which are two dimensions of the Classroom Assessment Scoring System (CLASS). School classrooms are highly cluttered audiovisual scenes containing many overlapping faces and voices. Due to the difficulty of labeling them (reliable coding requires weeks of training) and their sensitive nature (students and teachers may be in stressful or potentially embarrassing situations), CLASS- labeled classroom video datasets are scarce, and their labels are sparse (just a few labels per 15-minute video dip). Thus, the overarching challenge was how to harness modern deep perceptual architectures despite the paucity of labeled data. Through training low-level CNN-based facial attribute detectors (facial expression & adult/child) as well as a direct audio-to- climate regressor, and by integrating low-level information over time using a Bi-LSTM, we constructed automated detectors of positive and negative classroom climate with accuracy (10- fold cross-validation Pearson correlation on 241 CLASS-labeled videos) of 0.40 and 0.51, respectively. These numbers are superior to what we obtained using shallower architectures. This work represents the first automated system designed to detect specific dimensions of the CLASS. 

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3. DiVa-360: The Dynamic Visual Dataset for Immersive Neural Fields

   Cheng-You Lu*, Peisen Zhou* ( June 2024 , The IEEE/CVF Conference on Computer Vision and Pattern Recognition 2024)

   Advances in neural fields are enablling high-fidelity capture of shape and appearance of dynamic 3D scenes. However, this capbabilities lag behind those offered by conventional representations such as 2D videos because of algorithmic challenges and the lack of large-scale multi-view real-world datasets. We address the dataset limitations with DiVa-360, a real-world 360° dynamic visual dataset that contains synchronized high-resolution and long-duration multi-view video sequences of table-scale scenes captured using a customized low-cost system with 53 cameras. It contains 21 object-centric sequences categorized by different motion types, 25 intricate hand-object interaction sequences, and 8 long-duration sequences for a total of 17.4M frames. In addition, we provide foreground-background segmentation masks, synchronized audio, and text descriptions. We benchmark the state-of-the-art dynamic neural field methods on DiVa-360 and provide insights about existing methods and future challenges on long-duration neural field capture. 

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4. First-Person View Hand Segmentation of Multi-Modal Hand Activity Video Dataset.

   Sangpil Kim, Hyung-Gun Chi ( September 2020 , BMVC 2020)

   null (Ed.)

   First-person-view videos of hands interacting with tools are widely used in the computer vision industry. However, creating a dataset with pixel-wise segmentation of hands is challenging since most videos are captured with fingertips occluded by the hand dorsum and grasped tools. Current methods often rely on manually segmenting hands to create annotations, which is inefficient and costly. To relieve this challenge, we create a method that utilizes thermal information of hands for efficient pixel-wise hand segmentation to create a multi-modal activity video dataset. Our method is not affected by fingertip and joint occlusions and does not require hand pose ground truth. We show our method to be 24 times faster than the traditional polygon labeling method while maintaining high quality. With the segmentation method, we propose a multi-modal hand activity video dataset with 790 sequences and 401,765 frames of "hands using tools" videos captured by thermal and RGB-D cameras with hand segmentation data. We analyze multiple models for hand segmentation performance and benchmark four segmentation networks. We show that our multi-modal dataset with fusing Long-Wave InfraRed (LWIR) and RGB-D frames achieves 5% better hand IoU performance than using RGB frames. 

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5. Video-zilla: An Indexing Layer for Large-Scale Video Analytics

   https://doi.org/10.1145/3514221.3517840  

   Hu, Bo ; Guo, Peizhen ; Hu, Wenjun ( June 2022 , SIGMOD'22)

   Pervasive deployment of surveillance cameras today poses enormous scalability challenges to video analytics systems operating over many camera feeds. Currently, there are few indexing tools to organize video feeds beyond what is provided by a standard file system. Recent video analytic systems implement application-specific frame profiling and sampling techniques to reduce the number of raw videos processed, leveraging frame-level redundancy or manually labeled spatial-temporal correlation between cameras. This paper presents Video-zilla, a standalone indexing layer between video query systems and a video store to organize video data. We propose a video data unit abstraction, semantic video stream (SVS), based on a notion of distance between objects in the video. SVS implicitly captures scenes, which is missing from current video content characterization and a middle ground between individual frames and an entire camera feed. We then build a hierarchical index that exposes the semantic similarity both within and across camera feeds, such that Video-zilla can quickly cluster video feeds based on their content semantics without manual labeling. We implement and evaluate Video-zilla in three use cases: object identification queries, clustering for training specialized DNNs, and archival services. In all three cases, Video-zilla reduces the time complexity of inter-camera video analytics from linear with the number of cameras to sublinear, and reduces query resource usage by up to 14x compared to using frame-level or spatial-temporal similarity built into existing query systems. 

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