7236201
Catadioptric self-calibration
We have assembled a standalone, movable system that can capture long sequences of omnidirectional images (up to 1,500 images at 6.7 Hz and a resolution of 1140/spl times/090). The goal of this system is to reconstruct complex large environments, such as an entire floor of a building, from the captured images only. In this paper, we address the important issue of how to calibrate such a system. Our method uses images of the environment to calibrate the camera, without the use of any special calibration pattern, knowledge of camera motion, or knowledge of scene geometry. It uses the consistency of pairwise tracked point features across a sequence based on the characteristics of catadioptric imaging. We also show how the projection equation for this catadioptric camera can be formulated to be equivalent to that of a typical rectilinear perspective camera with just a simple transformation.
16190492
Noise Estimation from a Single Image
In order to work well, many computer vision algorithms require that their parameters be adjusted according to the image noise level, making it an important quantity to estimate. We show how to estimate an upper bound on the noise level from a single image based on a piecewise smooth image prior model and measured CCD camera response functions. We also learn the space of noise level functions how noise level changes with respect to brightness and use Bayesian MAP inference to infer the noise level function from a single image. We illustrate the utility of this noise estimation for two algorithms: edge detection and featurepreserving smoothing through bilateral filtering. For a variety of different noise levels, we obtain good results for both these algorithms with no user-specified inputs.
40596005
Survey of image-based representations and compression techniques
We survey the techniques for image-based rendering (IBR) and for compressing image-based representations. Unlike traditional three-dimensional (3-D) computer graphics, in which 3-D geometry of the scene is known, IBR techniques render novel views directly from input images. IBR techniques can be classified into three categories according to how much geometric information is used: rendering without geometry, rendering with implicit geometry (i.e., correspondence), and rendering with explicit geometry (either with approximate or accurate geometry). We discuss the characteristics of these categories and their representative techniques. IBR techniques demonstrate a surprising diverse range in their extent of use of images and geometry in representing 3-D scenes. We explore the issues in trading off the use of images and geometry by revisiting plenoptic-sampling analysis and the notions of view dependency and geometric proxies. Finally, we highlight compression techniques specifically designed for image-based representations. Such compression techniques are important in making IBR techniques practical.
2096181
Video editing using figure tracking and image-based rendering
We describe a new approach to video editing based on the semi-automatic segmentation of video into multiple layers and the composition of layers using image-based rendering. Using figure tracking and background motion estimation, we can segment a moving figure and reconstruct the background. Using geometrically-correct pixel reprojection, layers can be composited on the basis of the geometry of the underlying scene and the position of a virtual camera. We have implemented a prototype editing system called SpliceWorld.
44673585
Characterization of Errors in Compositing Panoramic Images
A panoramic image has a 360° horizontal field of view, and it can provide the viewer the impression of being immersed in the scene. A panorama is created by first taking a sequence of images while rotating the camera about a vertical axis. These images are then projected onto a cylindrical surface before being seamlessly composited. The cross-sectional circumference of the cylindrical panorama is called thecompositing length. This work characterizes the error in compositing panoramic images due to errors in some of the intrinsic parameters. The intrinsic camera parameters that are considered are the camera focal length and the radial distortion coefficient. We show that the error in the compositing length is more sensitive to the error in the camera focal length. Especially important is the discovery that the relative error in compositing length is always smaller than the relative error in the focal length. This means that the error in focal length can be corrected by iteratively using the composited length to compute a new and more correct focal length. Thiscompositing approach to camera calibrationhas the advantages of not requiring both feature detection and separate prior calibration.
47117010
Stylizing 2.5-D video
In recent years considerable interest has been given to non-photorealistic rendering of photographs, video, and 3D models for illustrative or artistic purposes. Conventional 2D inputs such as photographs and video are easy to create and capture, while 3D models allow for a wider variety of stylization techniques, such as cross-hatching. In this paper, we propose using video with depth information (2.5-D video) to combine the advantages of 2D and 3D input. 2.5-D video is becoming increasingly easy to capture, and with the additional depth information, stylization techniques that require shape information can be applied. However, because 2.5-D video contains only limited shape information and 3D correspondence over time is unknown, it is difficult to create temporally coherent stylized animations directly from raw 2.5-D video. In this paper, we present techniques for processing 2.5-D video to overcome these drawbacks, and demonstrate several styles that can be created using these techniques.
16508634
SmartClick: An enabler for human-centered wireless Web service
Recently wireless Web services have been rapidly growing as a new way of information service. As the wireless Internet access grows, so do e-commerce opportunities through the wireless Web services. Wireless Internet access has inherent limitations since most handheld devices have much less display and means of operations. This imposes a particular problem to the design of mobile information services in terms of information and service navigation. In this paper, a novel approach called SmartClick is presented to achieve user-centered wireless Web services. SmartClick enables users to explicitly express their intentions or preferences with minimal clicks (user interaction). SmartClick with a middleware support provides users a way to get the desired Web contents more efficiently and easily.
5947702
Fast timing simulation of transient faults in digital circuits
Transient fault simulation is an important verification activity for circuits used in critical applications since such faults account for over 80% of all system failures. This paper presents a timing level transient fault simulator that bridges the gap between electrical and gate-level transient fault simulators. A generic MOS circuit primitive and analytical solutions of node differential equations are used to perform transistor level simulation with accurate MOS-FET models. The transient fault is modeled by a piecewise quadratic injected current waveform; this retains the electrical nature of the transient fault and provides SPICE-like accuracy. Detailed comparisons with SPICE3 show the accuracy of this technique and speedups of two orders of magnitude are observed for circuits containing up to 2000 transistors. Latched error distributions of the benchmark circuits are also provided.
8305231
Packet-pair bandwidth estimation: stochastic analysis of a single congested node
We examine the problem of estimating the capacity of bottleneck links and available bandwidth of end-to-end paths under non-negligible cross-traffic conditions. We present a simple stochastic analysis of the problem in the context of a single congested node and derive several results that allow the construction of asymptotically-accurate bandwidth estimators. We first develop a generic queuing model of an Internet router and solve the estimation problem assuming renewal cross-traffic at the bottleneck link. Noticing that the renewal assumption on Internet flows is too strong, we investigate an alternative filtering solution that asymptotically converges to the desired values of the bottleneck capacity and available bandwidth under arbitrary (including non-stationary) cross-traffic. This is one of the first methods that simultaneously estimates both types of bandwidth and is provably accurate. We finish the paper by discussing the impossibility of a similar estimator for paths with two or more congested routers.
8347342
Keyword-based document clustering
Document clustering is an aggregation of related documents to a cluster based on the similarity evaluation task between documents and the representatives of clusters. Terms and their discriminating features of terms are the clue to the clustering and the discriminating features are based on the term and document frequencies. Feature selection method on the basis of frequency statistics has a limitation to the enhancement of the clustering algorithm because it does not consider the contents of the cluster objects. In this paper, we adopt a content-based analytic approach to refine the similarity computation and propose a keyword-based clustering algorithm. Experimental results show that content-based keyword weighting outperforms frequency-based weighting method.
16869035
An approach to virtual allocation in storage systems
This article presents virtual allocation, a scheme for flexible storage allocation. Virtual allocation separates storage allocation from the file system. It employs an allocate-on-write strategy which lets applications fit into the actual usage of storage space, without regard to the configured file system size. This improves flexibility by allowing storage space to be shared across different file systems. This article presents the design of virtual allocation and its evaluation through benchmarks. To illustrate our approach, we implemented a prototype system on PCs running Linux. We present the results from the prototype implementation and its evaluation.