mtybilly/Instruct2DS huggingface dataset:
Riemannian Coding and Dictionary Learning: Kernels to the Rescue
Authors: Mathieu Salzmann Mehrtash Harandi
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: While sparse coding on non-flat Riemannian manifolds has recently become increasingly popular, existing solutions either are dedicated to specific manifolds, or rely on optimization problems that are difficult to solve, especially when it comes to dictionary learning. In this paper, we propose to make use of kernels to perform coding and dictionary learning on Riemannian manifolds. To this end, we introduce a general Riemannian coding framework with its kernel-based counterpart. This lets us (i) generalize beyond the special case of sparse coding; (ii) introduce efficient solutions to two coding schemes; (iii) learn the kernel parameters; (iv) perform unsupervised and supervised dictionary learning in a much simpler manner than previous Riemannian coding methods. We demonstrate the effectiveness of our approach on three different types of non-flat manifolds, and illustrate its generality by applying it to Euclidean spaces, which also are Riemannian manifolds.
Scalable Structure From Motion for Densely Sampled Videos
Authors: Hendrik P. A. Lensch, Oliver Wang, Marc Pollefeys, Alexander Sorkine-Hornung Benjamin Resch
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Videos consisting of thousands of high resolution frames are challenging for existing structure from motion (SfM) and simultaneous-localization and mapping (SLAM) techniques. We present a new approach for simultaneously computing extrinsic camera poses and 3D scene structure that is capable of handling such large volumes of image data. The key insight behind this paper is to effectively exploit coherence in densely sampled video input. Our technical contributions include robust tracking and selection of confident video frames, a novel window bundle adjustment, frame-to-structure verification for globally consistent reconstructions with multi-loop closing, and utilizing efficient global linear camera pose estimation in order to link both consecutive and distant bundle adjustment windows. To our knowledge we describe the first system that is capable of handling high resolution, high frame-rate video data with close to realtime performance. In addition, our approach can robustly integrate data from different video sequences, allowing multiple video streams to be simultaneously calibrated in an efficient and globally optimal way. We demonstrate high quality alignment on large scale challenging datasets, e.g., 2-20 megapixel resolution at frame rates of 25-120 Hz with thousands of frames.
Parsing Occluded People by Flexible Compositions
Authors: Alan L. Yuille Xianjie Chen
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: This paper presents an approach to parsing humans when there is significant occlusion. We model humans using a graphical model which has a tree structure building on recent work [32, 6] and exploit the connectivity prior that, even in presence of occlusion, the visible nodes form a connected subtree of the graphical model. We call each connected subtree a flexible composition of object parts. This involves a novel method for learning occlusion cues. During inference we need to search over a mixture of different flexible models. By exploiting part sharing, we show that this inference can be done extremely efficiently requiring only twice as many computations as searching for the entire object (i.e., not modeling occlusion). We evaluate our model on the standard benchmarked "We Are Family" Stickmen dataset and obtain significant performance improvements over the best alternative algorithms.
Joint Calibration of Ensemble of Exemplar SVMs
Authors: Alexander Vezhnevets, Olga Russakovsky, Vittorio Ferrari Davide Modolo
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: We present a method for calibrating the Ensemble of Exemplar SVMs model. Unlike the standard approach, which calibrates each SVM independently, our method optimizes their joint performance as an ensemble. We formulate joint calibration as a constrained optimization problem and devise an efficient optimization algorithm to find its global optimum. The algorithm dynamically discards parts of the solution space that cannot contain the optimum early on, making the optimization computationally feasible. We experiment with EE-SVM trained on state-of-the-art CNN descriptors. Results on the ILSVRC 2014 and PASCAL VOC 2007 datasets show that (i) our joint calibration procedure outperforms independent calibration on the task of classifying windows as belonging to an object class or not; and (ii) this improved window classifier leads to better performance on the object detection task.
Holistic 3D Scene Understanding From a Single Geo-Tagged Image
Authors: Sanja Fidler, Raquel Urtasun Shenlong Wang
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: In this paper we are interested in exploiting geographic priors to help outdoor scene understanding. Towards this goal we propose  a holistic approach that reasons jointly about 3D object detection, pose estimation, semantic segmentation as well as depth reconstruction from a single image. Our approach takes  advantage of  large-scale crowd-sourced maps to generate dense geographic, geometric and semantic priors by rendering the 3D world. We demonstrate the effectiveness of our holistic model on the challenging KITTI dataset, and show significant improvements over the baselines in all metrics and tasks.
A Large-Scale Car Dataset for Fine-Grained Categorization and Verification
Authors: Ping Luo, Chen Change Loy, Xiaoou Tang Linjie Yang
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: This paper aims to highlight vision related tasks centered around "car", which has been largely neglected by vision community in comparison to other objects. We show that there are still many interesting car-related problems and applications, which are not yet well explored and researched. To facilitate future car-related research, in this paper we present our on-going effort in collecting a large-scale dataset, "CompCars", that covers not only different car views, but also their different internal and external parts, and rich attributes. Importantly, the dataset is constructed with a cross-modality nature, containing a surveillancenature set and a web-nature set. We further demonstrate a few important applications exploiting the dataset, namely car model classification, car model verification, and attribute prediction. We also discuss specific challenges of the car-related problems and other potential applications that worth further investigations. The latest dataset can be downloaded at http://mmlab.ie.cuhk.edu.hk/datasets/comp_cars/index.html
DeepContour: A Deep Convolutional Feature Learned by Positive-Sharing Loss for Contour Detection
Authors: Xinggang Wang, Yan Wang, Xiang Bai, Zhijiang Zhang Wei Shen
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Contour detection serves as the basis of a variety of computer vision tasks such as image segmentation and object recognition. The mainstream works to address this problem focus on designing engineered gradient features. In this work, we show that contour detection accuracy can be improved by instead making the use of the deep features learned from convolutional neural networks (CNNs). While rather than using the networks as a blackbox feature extractor, we customize the training strategy by partitioning contour (positive) data into subclasses and fitting each subclass by different model parameters. A new loss function, named positive-sharing loss, in which each subclass shares the loss for the whole positive class, is proposed to learn the parameters. Compared to the sofmax loss function, the proposed one, introduces an extra regularizer to emphasizes the losses for the positive and negative classes, which facilitates to explore more discriminative features. Our experimental results demonstrate that learned deep features can achieve top performance on Berkeley Segmentation Dataset and Benchmark (BSDS500) and obtain competitive cross dataset generalization result on the NYUD dataset.
Convolutional Feature Masking for Joint Object and Stuff Segmentation
Authors: Kaiming He, Jian Sun Jifeng Dai
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: The topic of semantic segmentation has witnessed considerable progress due to the powerful features learned by convolutional neural networks (CNNs). The current leading approaches for semantic segmentation exploit shape information by extracting CNN features from masked image regions. This strategy introduces artificial boundaries on the images and may impact the quality of the extracted features. Besides, the operations on the raw image domain require to compute thousands of networks on a single image, which is time-consuming.  In this paper, we propose to exploit shape information via masking convolutional features. The proposal segments (e.g., super-pixels) are treated as masks on the convolutional feature maps. The CNN features of segments are directly masked out from these maps and used to train classifiers for recognition. We further propose a joint method to handle objects and "stuff" (e.g., grass, sky, water) in the same framework. State-of-the-art results are demonstrated on the challenging PASCAL VOC benchmarks, with a compelling computational speed.
A Fixed Viewpoint Approach for Dense Reconstruction of Transparent Objects
Authors: Kwan-Yee K. Wong, Miaomiao Liu Kai Han
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: This paper addresses the problem of reconstructing the surface shape of transparent objects. The difficulty of this problem originates from the viewpoint dependent appearance of a transparent object, which quickly makes reconstruction methods tailored for diffuse surfaces fail disgracefully. In this paper, we develop a fixed viewpoint approach for dense surface reconstruction of transparent objects based on refraction of light. We introduce a simple setup that allows us alter the incident light paths before light rays enter the object, and develop a method for recovering the object surface based on reconstructing and triangulating such incident light paths. Our proposed approach does not need to model the complex interactions of light as it travels through the object, neither does it assume any parametric form for the shape of the object nor the exact number of refractions and reflections taken place along the light paths. It can therefore handle transparent objects with a complex shape and structure, with unknown and even inhomogeneous refractive index. Experimental results on both synthetic and real data are presented which demonstrate the feasibility and accuracy of our proposed approach.
Low-Level Vision by Consensus in a Spatial Hierarchy of Regions
Authors: Ying Xiong, Steven J. Gortler, Todd Zickler Ayan Chakrabarti
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: We introduce a multi-scale framework for low-level vision, where the goal is estimating physical scene values from image data---such as depth from stereo image pairs. The framework uses a dense, overlapping set of image regions at multiple scales and a ``local model,'' such as a slanted-plane model for stereo disparity, that is expected to be valid piecewise across the visual field. Estimation is cast as optimization over a dichotomous mixture of variables, simultaneously determining which regions are inliers with respect to the local model (binary variables) and the correct co-ordinates in the local model space for each inlying region (continuous variables). When the regions are organized into a multi-scale hierarchy, optimization can occur in an efficient and parallel architecture, where distributed computational units iteratively perform calculations and share information through  sparse connections between parents and children. The framework performs well on a standard benchmark for binocular stereo, and it produces a distributional scene representation that is appropriate for combining with higher-level reasoning and other low-level cues.
Line Drawing Interpretation in a Multi-View Context
Authors: Florent Lafarge, Adrien Bousseau Jean-Dominique Favreau
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Many design tasks involve the creation of new objects in the context of an existing scene. Existing work in computer vision only provides partial support for such tasks. On the one hand, multi-view stereo algorithms allow the reconstruction of real-world scenes, while on the other hand algorithms for line-drawing interpretation do not take context into account. Our work combines the strength of these two domains to interpret line drawings of imaginary objects drawn over photographs of an existing scene. The main challenge we face is to identify the existing 3D structure that correlates with the line drawing while also allowing the creation of new structure that is not present in the real world. We propose a labeling algorithm to tackle this problem, where some of the labels capture dominant orientations of the real scene while a free label allows the discovery of new orientations in the imaginary scene. We illustrate our algorithm by interpreting line drawings for urban planing, home remodeling, furniture design and cultural heritage.
Toward User-Specific Tracking by Detection of Human Shapes in Multi-Cameras
Authors: Edmond Boyer, Bibiana do Canto Angonese, Nassir Navab, Slobodan Ilic Chun-Hao Huang
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Human shape tracking consists in fitting a template model to temporal sequences of visual observations. It usually comprises an association step, that finds correspondences between the model and the input data, and a deformation step, that fits the model to the observations given correspondences. Most current approaches find their common ground with the Iterative-Closest-Point (ICP) algorithm, which facilitates the association step with local distance considerations. It fails when large deformations occur, and errors in the association tend to propagate over time. In this paper, we propose a discriminative alternative for the association, that leverages random forests to infer correspondences in one shot. It allows for large deformations and prevents tracking errors from accumulating. The approach is successfully integrated to a surface tracking framework that recovers human shapes and poses jointly. When combined with ICP, this discriminative association proves to yield better accuracy in registration, more stability when tracking over time, and faster convergence. Evaluations on existing datasets demonstrate the benefits with respect to the state-of-the-art.
Intra-Frame Deblurring by Leveraging Inter-Frame Camera Motion
Authors: Jianchao Yang Haichao Zhang
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Camera motion introduces motion blur, degrading the quality of  video. A video deblurring method is proposed based on two observations: (i) camera motion within capture of each individual frame leads to motion blur; (ii) camera motion between frames yields  inter-frame mis-alignment that can  be exploited for blur removal. The proposed method effectively leverages the information distributed across multiple video frames  due to camera motion, jointly estimating the motion between consecutive frames and blur within each frame. This joint analysis is crucial for achieving effective restoration by leveraging temporal information. Extensive experiments are carried out on  synthetic data as well as real-world blurry videos. Comparisons with several state-of-the-art methods verify the effectiveness of the proposed method.
Salient Object Subitizing
Authors: Shugao Ma, Mehrnoosh Sameki, Stan Sclaroff, Margrit Betke, Zhe Lin, Xiaohui Shen, Brian Price, Radomir Mech Jianming Zhang
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: People can immediately and precisely identify 1, 2, 3 or 4 items by a simple glance. The phenomenon, known as Subitizing, inspires us to pursue the task of Salient Object Subitizing (SOS), i.e. predicting the existence and the number of salient objects in a scene using holistic cues. To study this problem, we propose a new image dataset  annotated by Amazon Mechanical Turk. We show that  for a substantial proportion of our dataset,  there is a high labeling consistency among different subjects, even when a very limited viewing time (0.5s) is given. On our dataset, the baseline method using the global Convolutional Neural Network (CNN) feature achieves 94% recall rate in detecting the existence of salient objects, and 42-82% recall rate  (chance is 20%) in predicting the number of salient objects (1, 2, 3, and 4+), without resorting to any object localization process. Finally, we demonstrate the usefulness of the proposed subitizing technique in two computer vision applications: salient object detection and object proposal.
Hierarchical-PEP Model for Real-World Face Recognition
Authors: Gang Hua Haoxiang Li
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Pose variation remains one of the major factors adversely affect the accuracy of real-world face recognition systems. Inspired by the recently proposed probabilistic elastic part (PEP) model and the success of the deep hierarchical architecture in a number of visual tasks, we propose the Hierarchical-PEP model to approach the unconstrained face recognition problem. We apply the PEP model hierarchically to decompose a face image into face parts at different levels of details to build pose-invariant part-based face representations. Following the hierarchy from bottom-up, we stack the face part representations at each layer, discriminatively reduce its dimensionality, and hence aggregate the face part representations layer-by-layer to build a compact and invariant face representation. The Hierarchical-PEP model exploits the fine-grained structures of the face parts at different levels of details to address the pose variations. It is also guided by supervised information in constructing the face part/face representations. We empirically verify the Hierarchical-PEP model on two public benchmarks (i.e., the LFW and YouTube Faces) and a face recognition challenge (i.e., the PaSC grand challenge) for image-based and video-based face verification. The state-of-the-art performance demonstrates the potential of our method.
The Common Self-Polar Triangle of Concentric Circles and Its Application to Camera Calibration
Authors: Hui Zhang, Yiu-ming Cheung Haifei Huang
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: In projective geometry, the common self-polar triangle has often been used to discuss the position relationship of two planar conics. However, there are few researches on the properties of the common self-polar triangle, especially when the two planar conics are special conics. In this paper, we explore the properties of the common self-polar triangle, when the two conics happen to be concentric circles. We show there exist infinite many common self-polar triangles of two concentric circles, and provide a method to locate the vertices of these triangles. By investigating all these triangles, we find that they encode two important properties. The first one is all triangles share one common vertex, and the opposite side of the common vertex lies on the same line, which are the circle center and the line at the infinity of the support plane. The second is all triangles are right triangles. Based on these two properties, the imaged circle center and the varnishing line of support plane can be recovered simultaneously, and many conjugate pairs on vanishing line can be obtained. These allow to induce good constraints on the image of absolute conic. We evaluate two calibration algorithms, whereby accurate results are achieved.  The main contribution of this paper is that we initiate a new perspective to look into circle-based camera calibration problem. We believe that other calibration methods using different circle patterns can benefit from this perspective, especially for the patterns which involve more than two circles.
Taking a Deeper Look at Pedestrians
Authors: Mohamed Omran, Rodrigo Benenson, Bernt Schiele Jan Hosang
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: The only goal of the abstract is to the answer the question: why should I read this paper? In this paper we study the use of convolutional neural networks (convnets) for the task of pedestrian detection. Despite their recent diverse successes, convnets historically underperform compared to other pedestrian detectors. We deliberately omit explicitly modelling the problem into the network (e.g. parts or occlusion modelling) and show that we can reach competitive performance without bells and whistles. In a wide range of experiments we analyse small and big convnets, their architectural choices, parameters, and the influence of different training data, including pre-training on surrogate tasks.  We present the best convnet detectors on the Caltech and KITTI dataset. On Caltech our convnets reach top performance both for the Caltech1x and Caltech10x training setup. Using additional data at training time our strongest convnet model is competitive to detectors that use instead additional data at test time.
Learning to Segment Moving Objects in Videos
Authors: Pablo Arbelaez, Panna Felsen, Jitendra Malik Katerina Fragkiadaki
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: We segment  moving objects in  videos by ranking  spatio-temporal segment  proposals according to ``moving objectness'';  how likely they are to contain a moving  object.   In each video frame, we compute segment proposals   using multiple figure-ground segmentations on per frame motion  boundaries.  We rank them with a   Moving Objectness Detector  trained on  image and motion fields to detect moving objects and  discard over/under segmentations or background parts of the scene.  We extend the top ranked segments  into   spatio-temporal tubes using random walkers on  motion affinities of dense point trajectories.    Our final tube ranking consistently   outperforms previous segmentation methods in the two largest video segmentation benchmarks currently available,  for any number of proposals.   Further, our per frame moving object proposals increase  the  detection rate up to 7\% over  previous state-of-the-art static  proposal methods.
GMMCP Tracker: Globally Optimal Generalized Maximum Multi Clique Problem for Multiple Object Tracking
Authors: Shayan Modiri Assari, Mubarak Shah Afshin Dehghan
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Data association is the backbone to many multiple object tracking (MOT) methods. In this paper we formulate data association as a Generalized Maximum Multi Clique problem (GMMCP). We show that this is the ideal case of modeling tracking in real world scenario where all the pairwise relationships between targets in a batch of frames are taken into account. Previous works assume simplified version of our tracker either in problem formulation or problem optimization. However, we propose a solution using GMMCP where no simplification is assumed in either steps. We show that the NP hard problem of GMMCP can be formulated through Binary-Integer Program where for small and medium size MOT problems the solution can be found efficiently. We further propose a speed-up method, employing Aggregated Dummy Nodes for modeling occlusion and miss-detection, which reduces the size of the input graph without using any heuristics. We show that, using the speedup method, our tracker lends itself to real-time implementation which is plausible in many applications. We evaluated our tracker on six challenging sequences of Town Center, TUD-Crossing, TUD-Stadtmitte, Parking-lot 1, Parking-lot 2 and Parking-lot pizza and show favorable improvement against state of art.
Learning Graph Structure for Multi-Label Image Classification via Clique Generation
Authors: Qinfeng Shi, Anton van den Hengel, Chunhua Shen, Junbin Gao, Fuyuan Hu, Zhen Zhang Mingkui Tan
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Exploiting label dependency for multi-label image classification can significantly improve classification performance. Probabilistic Graphical Models are one of the primary methods for representing such dependencies. The structure of graphical models, however, is either determined heuristically or learned from very limited information. Moreover, neither of these approaches scales well to large or complex graphs. We propose a principled way to learn the structure of a graphical model by considering input features and labels, together with loss functions. We formulate this problem into a max-margin framework initially, and then transform it into a convex programming problem. Finally, we propose a highly scalable procedure that activates a set of cliques iteratively. Our approach exhibits both strong theoretical properties and a significant performance improvement over state-of-the-art methods on both synthetic and real-world data sets.
Matrix Completion for Resolving Label Ambiguity
Authors: Vishal M. Patel, Rama Chellappa Ching-Hui Chen
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: In real applications, data is not always explicitly-labeled. For instance, label ambiguity exists when we associate two persons appearing in a news photo with two names provided in the caption. We propose a matrix completion-based method for predicting the actual labels from the ambiguously labeled instances, and a standard supervised classifier can learn from the disambiguated labels to classify new data. We further generalize the method to handle the labeling constraints between instances when such prior knowledge is available. Compared to existing methods, our approach achieves 2.9% improvement on the labeling accuracy of the Lost dataset and comparable performance on the Labeled Yahoo! News dataset.
Video Magnification in Presence of Large Motions
Authors: Mohamed Hefeeda, Fredo Durand, William T. Freeman Mohamed Elgharib
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Video magnification reveals subtle variations that would be otherwise invisible to the naked eye. Current techniques require all motion in the video to be very small, which is unfortunately not always the case. Tiny yet meaningful motions are often combined with larger motions, such as the small vibrations of a gate as it rotates, or the microsaccades in a moving eye. We present a layer-based video magnification approach that can amplify small motions within large ones. An examined region/layer is temporally aligned and subtle variations are magnified. Matting is used to magnify only region of interest while maintaining integrity of nearby sites. Results show handling larger motions, larger amplification factors and significant reduction in artifacts over state of the art.
Flying Objects Detection From a Single Moving Camera
Authors: Vincent Lepetit, Pascal Fua Artem Rozantsev
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: We propose an approach to detect flying objects such as UAVs and aircrafts when they occupy a small portion of the field of view, possibly moving against complex backgrounds, and are filmed by a camera that itself moves.  Solving such a difficult problem requires combining both appearance and motion cues. To this end we propose a regression-based approach to motion stabilization of local image patches that allows us to achieve effective classifica- tion on spatio-temporal image cubes and outperform state- of-the-art techniques.  As the problem is relatively new, we collected two chal- lenging datasets for UAVs and Aircrafts, which can be used as benchmarks for flying objects detection and vision- guided collision avoidance.
Line-Based Multi-Label Energy Optimization for Fisheye Image Rectification and Calibration
Authors: Jian Yao, Menghan Xia, Kai Li, Yi Zhang, Yaping Liu Mi Zhang
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Fisheye image rectification and estimation of intrinsic parameters for real scenes have been addressed in the literature by using line information on the distorted images. In this paper, we propose an easily implemented fisheye image rectification algorithm with line constrains in the undistorted perspective image plane. A novel Multi-Label Energy Optimization (MLEO) method is adopted to merge short circular arcs sharing the same or the approximately same circular parameters and select long circular arcs for camera rectification. Further we propose an efficient method to estimate intrinsic parameters of the fisheye camera by automatically selecting three properly arranged long circular arcs from previously obtained circular arcs in the calibration procedure. Experimental results on a number of real images and simulated data show that the proposed method can achieve good results and outperforms the existing approaches and the commercial software in most cases.
Adaptive Eye-Camera Calibration for Head-Worn Devices
Authors: Rohit Kumar Gupta, Jan-Michael Frahm David Perra
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: We present a novel, continuous, locally optimal calibration scheme for use with head-worn devices.  Current calibration schemes solve for a globally optimal model of the eye-device transformation by performing calibration on a per-user or once-per-use basis.  However, these calibration schemes are impractical for real-world applications because they do not account for changes in calibration during the time of use.  Our calibration scheme allows a head-worn device to calculate a locally optimal eye-device transformation on demand by computing an optimal model from a local window of previous frames. By leveraging naturally occurring interest regions within the user's environment, our system can calibrate itself without the user's active participation.  Experimental results demonstrate that our proposed calibration scheme outperforms the existing state of the art systems while being significantly less restrictive to the user and the environment.
Modeling Object Appearance Using Context-Conditioned Component Analysis
Authors: Neill D.F. Campbell, Simon J.D. Prince, Jan Kautz Daniyar Turmukhambetov
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Subspace models have been very successful at modeling the appearance of structured image datasets when the visual objects have been aligned in the images (e.g., faces). Even with extensions that allow for global transformations or dense warps of the image, the set of visual objects whose appearance may be modeled by such methods is limited. They are unable to account for visual objects where occlusion leads to changing visibility of different object parts (without a strict layered structure) and where a one-to-one mapping between parts is not preserved. For example bunches of bananas contain different numbers of bananas but each individual banana shares an appearance subspace.   In this work we remove the image space alignment limitations of existing subspace models by conditioning the models on a shape dependent context that allows for the complex, non-linear structure of the appearance of the visual object to be captured and shared. This allows us to exploit the advantages of subspace appearance models with non-rigid, deformable objects whilst also dealing with complex occlusions and varying numbers of parts. We demonstrate the effectiveness of our new model with examples of structured inpainting and appearance transfer.
Displets: Resolving Stereo Ambiguities Using Object Knowledge
Authors: Andreas Geiger Fatma Guney
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Stereo techniques have witnessed tremendous progress over the last decades, yet some aspects of the problem still remain challenging today. Striking examples are reflecting and textureless surfaces which cannot easily be recovered using traditional local regularizers. In this paper, we therefore propose to regularize over larger distances using object-category specific disparity proposals (displets) which we sample using inverse graphics techniques based on a sparse disparity estimate and a semantic segmentation of the image. The proposed displets encode the fact that objects of certain categories are not arbitrarily shaped but typically exhibit regular structures. We integrate them as non-local regularizer for the challenging object class 'car' into a superpixel based CRF framework and demonstrate its benefits on the KITTI stereo evaluation. At time of submission, our approach ranks first across all KITTI stereo leaderboards.
Time-to-Contact From Image Intensity
Authors: Fumihiko Sakaue, Jun Sato Yukitoshi Watanabe
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: It is known that time-to-contact toward objects can be estimated just from changes in the object size in camera images, and we do not need any additional information, such as camera parameters and motions.  However, the existing methods for measuring the time-to-contact are based on geometric image features, such as corners and edge lines, and thus they cannot be used when there are no geometric features in images. In this paper, we propose a new method for computing the time-to-contact from photometric information in images. When a light source moves in the 3D scene, an observed intensity changes according to the motion of the light source.  In this paper, we analyze the change in photometric information in images, and show that the time-to-contact can be estimated just from the changes in intensity in images. Our method does not need any additional information, such as radiance of light source, reflectance of object and orientation of object surface. The proposed method can be used in various applications, such as vehicle driver assistance.
Transferring a Semantic Representation for Person Re-Identification and Search
Authors: Timothy M. Hospedales, Tao Xiang Zhiyuan Shi
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Learning semantic attributes for person re-identification and  description-based person search has gained increasing interest due to attributes' great potential as a pose and view-invariant representation. However, existing attribute-centric approaches have thus far underperformed state-of-the-art conventional approaches. This is due to their non-scalable need for extensive domain (camera) specific annotation.  In this paper we present a new semantic attribute learning approach for person re-identification and search. Our model is trained on existing fashion photography datasets -- either weakly or strongly labelled. It can then be transferred and adapted to provide a powerful semantic description of surveillance person detections, without requiring any surveillance domain supervision. The resulting representation is useful for both unsupervised and supervised person re-identification, achieving state-of-the-art and near state-of-the-art performance respectively. Furthermore, as a semantic representation it allows description-based person search to be integrated within the same framework.
Robust Video Segment Proposals With Painless Occlusion Handling
Authors: Fuxin Li, Rahul Sukthankar, James M. Rehg Zhengyang Wu
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: We propose a robust algorithm to generate video segment proposals. The proposals generated by our method can start from any frame in the video and are robust to complete occlusions. Our method does not assume specific motion models and even has a limited capability to generalize across videos. We build on our previous least squares tracking framework, where image segment proposals are generated and tracked using learned appearance models. The innovation in our new method lies in the use of two efficient moves, the merge move and free addition, to efficiently start segments from any frame and track them through complete occlusions, without much additional computation. Segment size interpolation is used for effectively detecting occlusions.  We propose a new metric for evaluating video segment proposals on the challenging VSB-100 benchmark and present state-of-the-art results. Preliminary results are also shown for the potential use of our framework to track segments across different videos.
Face Alignment Using Cascade Gaussian Process Regression Trees
Authors: Hyunsin Park, Chang D. Yoo Donghoon Lee
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: In this paper, we propose a face alignment method that uses cascade Gaussian process regression trees (cGPRT) constructed by combining Gaussian process regression trees (GPRT) in a cascade stage-wise manner. Here, GPRT is a Gaussian process with a kernel defined by a set of trees. The kernel measures the similarity between two inputs as the number of trees where the two inputs fall in the same leaves. Without increasing prediction time, the prediction of cGPRT can be performed in the same framework as the cascade regression trees (CRT) but with better generalization. Features for GPRT are designed using shape-indexed difference of Gaussian (DoG) filter responses sampled from local retinal patterns to increase stability and to attain robustness against geometric variances. Compared with the previous CRT-based face alignment methods that have shown state-of-the-art performances, cGPRT using shape-indexed DoG features performed best on the HELEN and 300-W datasets which are the most challenging dataset today.
Regularizing Max-Margin Exemplars by Reconstruction and Generative Models
Authors: Bjorn Ommer Jose C. Rubio
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Part-based models are one of the leading paradigms in visual recognition. In the absence of costly part annotations, associating and aligning different training instances of a part classifier and finding characteristic negatives is challenging and computationally demanding. To avoid this costly mining of training samples, we estimate separate generative models for negatives and positives and integrate them into a max-margin exemplar-based model. The generative model and a sparsity constraint on the correlation between spatially neighboring feature dimensions regularize the part filters during learning and improve their generalization to similar instances. To suppress inappropriate positive part samples, we project the classifier back into the image domain and penalize against deviations from the original exemplar image patch. The part filter is then optimized to i) discriminate against clutter, to ii) generalize to similar instances of the part, and iii) to yield a good reconstruction of the original image patch. Moreover, we propose an approximation for estimating the geometric margin so that learning large numbers of parts becomes feasible. Experiments show improved part localization, object recognition, and part-based reconstruction performance compared to popular exemplar-based approaches on PASCAL VOC
A Fast Algorithm for Elastic Shape Distances Between Closed Planar Curves
Authors: Javier Bernal, Charles R. Hagwood Gunay Dogan
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Effective computational tools for shape analysis are needed in many areas of science and engineering. We address this and propose a new fast iterative algorithm to compute the elastic geodesic distance between shapes of closed planar curves. The original algorithm for this has cubic time complexity with respect to the number of nodes per curve. Hence it is not suitable for large shape data sets. We aim for large-scale shape analysis and thus propose an iterative algorithm based on the original one but with quadratic time complexity. In practice, we observe subquadratic, almost linear running times, and that our algorithm scales very well with large numbers of nodes. The key to our algorithm is the decoupling of the optimization for the starting point and rotation from that of the reparametrization, and the development of fast dynamic programming and iterative nonlinear constrained optimization algorithms that work in tandem to compute optimal reparametrizations fast.
Reflection Removal for In-Vehicle Black Box Videos
Authors: In Kyu Park Christian Simon
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: In-vehicle black box camera becomes an popular equipment in many countries for security monitoring and event capturing. The readability of video contents is the most important capability, which is, however, often degraded due to the reflection on the windscreen. In this paper, we propose a novel method to remove the reflection on the windscreen in the in-vehicle black box videos. The main idea is to exploit spatio-temporal coherence of the reflection which shows that a vehicle moves forward while the reflection layer of internal object remains static. The average image prior is introduced by imposing a heavy-tail distribution with higher peak. The two layered scene is the base of the separation model. In order to remove the reflection, a cost non-convex function is developed based on this property and optimized. Experimental results demonstrate that the proposed approach successfully separates the layers in real black box videos.
Tree Quantization for Large-Scale Similarity Search and Classification
Authors: Victor Lempitsky Artem Babenko
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: We propose a new vector encoding scheme (tree quantization) that obtains lossy compact codes for high-dimensional vectors via tree-based dynamic programming. Similarly to several previous schemes such as product quantization, these codes correspond to codeword numbers within multiple codebooks. We propose an integer programming-based optimization that jointly recovers the coding tree structure and the codebooks by minimizing the compression error on a training dataset. In the experiments with diverse visual descriptors (SIFT, neural codes, Fisher vectors), tree quantization is shown to combine fast encoding and state-of-the-art accuracy in terms of the compression error, the retrieval performance, and the image classification error.
Integrating Parametric and Non-Parametric Models For Scene Labeling
Authors: Gang Wang, Zhen Zuo, Bing Wang, Lifan Zhao Bing Shuai
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: We adopt Convolutional Neural Networks (CNN) as our parametric model to learn discriminative features and classifiers for local patch classification. As visually similar pixels are indistinguishable from local context, we alleviate such ambiguity by putting a global scene constraint. We estimate the global potential in a non-parametric framework. Furthermore, a large margin based CNN metric learning method is proposed for better global potential estimation. The final pixel class prediction is performed by integrating local and global beliefs. Even without any post-processing, we achieve state-of-the-art on SiftFlow and competitive results on Stanford Background benchmark.
Mining Semantic Affordances of Visual Object Categories
Authors: Zhan Wang, Rada Mihalcea, Jia Deng Yu-Wei Chao
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Affordances are fundamental attributes of objects. Affordances reveal the functionalities of objects and the possible actions that can be performed on them. Understanding affordances is crucial for recognizing human activities in visual data and for robots to interact with the world.  In this paper we introduce the new problem of mining the knowledge of semantic affordance: given an object, determining whether an action can be performed on it. This is equivalent to connecting verb nodes and noun nodes in WordNet, or filling an affordance matrix encoding the plausibility of each action-object pair. We introduce a new benchmark with crowdsourced ground truth affordances on 20 PASCAL VOC object classes and 957 action classes.  We explore a number of approaches including text mining, visual mining, and collaborative filtering. Our analyses yield a number of significant insights that reveal the most effective ways of collecting knowledge of semantic affordances.
Causal Video Object Segmentation From Persistence of Occlusions
Authors: Vasiliy Karasev, Stefano Soatto Brian Taylor
Published in: IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2015 (Main Conference Track), 2015

Abstract: Occlusion relations inform the partition of the image domain into ``objects'' but are difficult to determine from a single image or short-baseline video. We show how long-term occlusion relations can be robustly inferred from video, and used within a convex optimization framework to segment the image domain into regions. We highlight the challenges in determining these occluder/occluded relations and ensuring regions remain temporally consistent, propose strategies to overcome them, and introduce an efficient numerical scheme to perform the partition directly on the pixel grid, without the need for superpixelization or other preprocessing steps.