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Circuits and Systems for Video Technology, IEEE Transactions on

Issue 2 • Date March 2000

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Displaying Results 1 - 17 of 17
  • Guest editorial

    Page(s): 185
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    Freely Available from IEEE
  • Erratum

    Page(s): 331
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    In the Guest Editorial of the December 1999 issue of this TRANSACTIONS, the last sentence in the biography of Rob Koenen should read as follows: "Dr. Koenen is an Associate Editor of IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY." View full abstract»

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  • Automatic reconstruction of stationary 3-D objects from multiple uncalibrated camera views

    Page(s): 261 - 277
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    A system for the automatic reconstruction of real-world objects from multiple uncalibrated camera views is presented. The camera position and orientation for all views, the 3-D shape of the rigid object, as well as the associated color information, are recovered from the image sequence. The system proceeds in four steps. First, the internal camera parameters describing the imaging geometry are calibrated using a reference object. Second, an initial 3-D description of the object is computed from two views. This model information is then used in a third step to estimate the camera positions for all available views using a novel linear 3-D motion and shape estimation algorithm. The main feature of this third step is the simultaneous estimation of 3-D camera-motion parameters and object shape refinement with respect to the initial 3-D model. The initial 3-D shape model exhibits only a few degrees of freedom and the object shape refinement is defined as flexible deformation of the initial shape model. Our formulation of the shape deformation allows the object texture to slide on the surface, which differs from traditional flexible body modeling. This novel combined shape and motion estimation using sliding texture considerably improves the calibration data of the individual views in comparison to fixed-shape model based camera-motion estimation. Since the shape model used for model based camera-motion estimation is only approximate, a volumetric 3-D reconstruction process is initiated in the fourth step that combines the information from ail views simultaneously. The recovered object consists of a set of voxels with associated color information that describes even fine structures and details of the object. New views of the object can be rendered from the recovered 3-D model, which has potential applications in virtual reality or multimedia systems and the emerging field of video coding using 3-D scene models View full abstract»

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  • Real-time display of virtual humans: levels of details and impostors

    Page(s): 207 - 217
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    Rendering and animating in real-time a multitude of articulated characters presents a real challenge, and few hardware systems are up to the task. Up to now, little research has been conducted to tackle the issue of real-time rendering of numerous virtual humans. This paper presents a hardware-independent technique that improves the display rate of animated characters by acting on the sole geometric and rendering information. We first review the acceleration techniques traditionally in use in computer graphics and highlight their suitability to articulated characters. We then show how impostors can be used to render virtual humans. We introduce concrete case studies that demonstrate the effectiveness of our approach. Finally, we tackle the visibility issue View full abstract»

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  • Sprite generation and coding in multiview image sequences

    Page(s): 302 - 311
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    A novel algorithm for the generation of background sprite images from multiview image sequences is presented. A dynamic programming algorithm, first proposed by Grammalidis and Strintzis (see IEEE Trans. Circuits Syst. Video Technol., vol.8, p.328-44, 1998) using a multiview matching cost, as well as pure geometrical constraints, is used to provide an estimate of the disparity field and to identify occluded areas. By combining motion, disparity, and occlusion information, a sprite image corresponding to the first (main) view at the first time instant is generated. Image pixels from other views that are occluded in the main view are also added to the sprite. Finally, the sprite coding method defined by MPEG-4 is extended for multiview image sequences based on the generated sprite. Experimental results are presented, demonstrating the performance of the proposed technique and comparing it with standard MPEG-4 coding methods applied independently to each view View full abstract»

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  • Subjective evaluation of stereoscopic images: effects of camera parameters and display duration

    Page(s): 225 - 233
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    Two experiments are presented that were aimed to investigate the effects of stereoscopic filming parameters and display duration on observers' judgements of naturalness and quality of stereoscopic images. The paper first presents a literature review of temporal factors in stereoscopic vision, with reference to stereoscopic displays. Several studies have indicated an effect of display duration on performance-oriented (criterion based) measures. The experiments reported were performed to extend the study of display duration from performance to appreciation-oriented measures. In addition, the present study aimed to investigate the effects of manipulating camera separation, convergence distance, and focal length on perceived quality and naturalness, In the first experiment, using display durations of both 5 and 10 s, 12 observers rated the naturalness of depth and the quality of depth for stereoscopic still images. The results showed no significant main effect of the display duration. A small yet significant shift between naturalness and quality was found for both duration conditions. This result replicated earlier findings, indicating that this is a reliable effect, albeit content-dependent. The second experiment was performed using display durations ranging from 1 to 15 s. The results of this experiment showed a small yet significant effect of display duration. Whereas longer display durations do not have a negative impact on the appreciative scores of optimally reproduced stereoscopic images, observers do give lower judgements to monoscopic images and stereoscopic images with unnatural disparity values as display duration increases. In addition, the results of both experiments provide support for the argument that stereoscopic camera toe-in should be avoided if possible View full abstract»

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  • Stereo image quality: effects of mixed spatio-temporal resolution

    Page(s): 188 - 193
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    We explored the response of the human visual system to mixed-resolution stereo video-sequences, in which one eye view was spatially or temporally low-pass filtered. It was expected that the perceived quality, depth, and sharpness would be relatively unaffected by low-pass filtering, compared to the case where both eyes viewed a filtered image. Subjects viewed two 10-second stereo video-sequences, in which the right-eye frames were filtered vertically (V) and horizontally (H) at 1/2 H, 1/2 V, 1/4 H, 1/4 V, 1/2 H 1/2 V, 1/2 H 1/4 V, 1/4 H 1/2 V, and 1/4 H 1/4 V resolution. Temporal filtering was implemented for a subset of these conditions at 1/2 temporal resolution, or with drop-and-repeat frames. Subjects rated the overall quality, sharpness, and overall sensation of depth. It was found that spatial filtering produced acceptable results: the overall sensation of depth was unaffected by low-pass filtering, while ratings of quality and of sharpness were strongly weighted towards the eye with the greater spatial resolution. By comparison, temporal filtering produced unacceptable results: field averaging and drop-and-repeat frame conditions yielded images with poor quality and sharpness, even though perceived depth was relatively unaffected. We conclude that spatial filtering of one channel of a stereo video-sequence may be an effective means of reducing the transmission bandwidth View full abstract»

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  • Automatic 3-D model synthesis from measured range data

    Page(s): 293 - 301
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    We propose an algorithm to construct a 3-D surface model from a set of range data, based on non-uniform rational B-splines (NURBS) surface-fitting technique. It is assumed that the range data is initially unorganized and scattered 3-D points, while their connectivity is also unknown. The proposed algorithm consists of three stages: initial model approximation employing K-means clustering, hierarchical decomposition of the initial model, and construction of the NURBS surface patch network. The initial model is approximated by both a polyhedral and triangular model. Then, the initial model is represented by a hierarchical graph, which is efficiently used to construct the G 1 continuous NURBS patch network of the whole object. Experiments are carried out on synthetic and real range data to evaluate the performance of the proposed algorithm. It is shown that the initial model as well as the NURBS patch network are constructed automatically with tolerable computation. The modeling error of the NURBS model is reduced to 10%, compared with the initial mesh model View full abstract»

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  • A family of single-user autostereoscopic displays with head-tracking capabilities

    Page(s): 234 - 243
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    We present prototypes of autostereoscopic displays which allow single users to experience stereoscopic vision without the need for special eye glasses or helmet-mounted displays. The design of the displays is based on lenticular raster plates and includes a number of novel concepts for tracking of raster plates or projection lenses to account for changes of the viewers position in front of the screen. Applications envisioned include 3-D multimedia desktop visualization for medical and biological imaging, design, and architecture, as well as computer games and 3-D virtual reality in general. Concepts and results for both high-resolution flat liquid-crystal panel monitors for PC desktop applications as well as large screen high resolution displays using rear-projection technology are discussed View full abstract»

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  • Overlapped block disparity compensation with adaptive windows for stereo image coding

    Page(s): 194 - 200
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    We propose a modified overlapped block-matching (OBM) scheme for stereo image coding. OBM has been used in video coding but, to the best of our knowledge, it has not been applied to stereo image coding to date. In video coding, OBM has proven useful in reducing blocking artifacts (since multiple vectors can be used for each block), while also maintaining most of the advantages of fixed-size block matching. There are two main novelties in this work. First, we show that OBM techniques can be successfully applied to stereo image coding. Second, we take advantage of the smoothness properties typically found in disparity fields to further improve the performance of OBM in this particular application. Specifically, we note that practical OBM approaches use noniterative estimation techniques, which produce lower quality estimates than iterative methods. By introducing smoothness constraints into the noniterative DV computation, we improve the quality of the estimated disparity as compared to standard noniterative OBM approaches. In addition, we propose a disparity estimation/compensation approach using adaptive windows with variable shapes, which results in a reduction in complexity. We provide experimental results that show that our proposed hybrid OBM scheme achieves a PSNR gain (about 1.5-2 dB) as compared to a simple block-based scheme, with some slight PSNR gains (about 0.2-0.5 dB) in a reduced complexity, as compared to an approach based on standard OBM with half-pixel accuracy View full abstract»

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  • Producing object-based special effects by fusing multiple differently focused images

    Page(s): 323 - 330
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    We propose a novel approach for producing special visual effects by fusing multiple differently focused images. This method differs from conventional image fusion techniques because it enables us to arbitrarily generate object-based visual effects such as blurring, enhancement, and shifting. Notably, the method does not need any segmentation. Using a linear imaging model, it directly generates the desired image from multiple differently focused images View full abstract»

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  • A study on scanning methods for a field-sequential stereoscopic display

    Page(s): 244 - 253
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    This paper focuses on the scanning methods of a field-sequential stereoscopic display system. We examined the advantages and disadvantages of several scanning methods to identify the most suitable one for the field-sequential stereoscopic display technique. An evaluation test using a system with 525 scanning lines and a 120-Hz field frequency was conducted. The results show that the picture quality of the 4:2 or 4:1 interlace method, which maintains high vertical resolution, is superior to that of the simple 2:1 interlace one. We also developed an experimental field-sequential stereoscopic system for HDTV with 1:2 interlacing and confirmed that it is possible to display high-quality stereoscopic HDTV pictures in full 1125-line vertical resolutions View full abstract»

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  • A post-processing technique for noise removal of range data

    Page(s): 201 - 206
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    Spurious range data pose a serious visualization problem with active light systems, as they can totally deform the acquired 3-D shapes. This work presents a technique for their detection based on geometrical considerations. The proposed method does not need extra hardware and can be used effectively for the provision of post-processing noise removal. The method has been extensively tested on real data. Its performance is discussed and demonstrated by examples View full abstract»

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  • A new flexible acquisition system of ray-space data for arbitrary objects

    Page(s): 218 - 224
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    Conventional ray-space acquisition systems require very precise mechanisms to control the small movement of cameras or objects. Most of them adopt camera with a gantry or a turntable. Although they are good for acquiring the ray-space of small objects, they are not suitable for ray-space acquisition of very large structures, such as a building, tower, etc. This paper proposes a new ray-space acquisition system which consists of a camera and a 3-D position and orientation sensor. It is not only a compact and easy-to-handle system, but is also free from limitations of size or shape, in principle. It can obtain any ray-space data as far as the camera is located within the coverage of the 3-D sensor. This paper describes our system and its specifications. Experimental results are also presented View full abstract»

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  • Geometry compression of 3-D mesh models using predictive two-stage quantization

    Page(s): 312 - 322
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    In conventional predictive quantization schemes for 3-D mesh geometry, excessively large residuals or prediction errors, although occasional, lead to visually unacceptable geometric distortion. This is due to the fact that they cannot limit the maximum quantization error within a given bound. In order to completely eliminate the visually unacceptable distortion caused by large residuals, we propose a predictive two-stage quantization scheme. This scheme is very similar to the conventional DPCM, except that the embedded quantizer is replaced by a series of two quantizers. Each quantizer output is further compressed by an arithmetic code. When applied to typical 3-D mesh models, the scheme performs much better than the conventional predictive quantization methods and, depending upon the input models, even than the MPEG-4 compression method for 3-D mesh geometry both in rate distortion sense and in subjective viewing View full abstract»

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  • Autostereoscopic 3-D video display using multiple light beams with scanning

    Page(s): 254 - 260
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    An autostereoscopic 3-D displaying technique that uses fan-likely placed multiple light beams in a light array with 2-D raster scanning is proposed. This technique is capable of displaying multiple perspective views at high resolution because the number of views only depends on the number of light beams, while the number of light beams does not depend on the resolution of each view. Moreover, dozens or hundreds of perspective views at an angular interval narrower than one degree can be produced if small light sources are used. On the basis of this technique, an experimental 3-D display system capable of producing 45-view video images at an angular interval of 0.5 degrees at a time is developed. Furthermore, the effectiveness of the technique is demonstrated by using this system View full abstract»

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  • Visible surface reconstruction with accurate localization of object boundaries

    Page(s): 278 - 292
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    A common limitation of many techniques for 3-D reconstruction from multiple perspective views is the poor quality of the results near the object boundaries. The interpolation process applied to “unstructured” 3-D data (“clouds” of non-connected 3-D points) plays a crucial role in the global quality of the 3-D reconstruction. We present a method for interpolating unstructured 3-D data, which is able to perform a segmentation of such data into different data sets that correspond to different objects. The algorithm is also able to perform an accurate localization of the boundaries of the objects. The method is based on an iterative optimization algorithm. As a first step, a set of surfaces and boundary curves are generated for the various objects. Then, the edges of the original images are used for refining such boundaries as best as possible. Experimental results with real data are presented for proving the effectiveness of the proposed algorithm View full abstract»

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Aims & Scope

The emphasis is focused on, but not limited to:
1. Video A/D and D/ A
2. Video Compression Techniques and Signal Processing
3. Multi-Dimensional Filters and Transforms
4. High Speed Real-Tune Circuits
5. Multi-Processors Systems—Hardware and Software
6. VLSI Architecture and Implementation for Video Technology 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Dan Schonfeld
Multimedia Communications Laboratory
ECE Dept. (M/C 154)
University of Illinois at Chicago (UIC)
Chicago, IL 60607-7053
tcsvt-eic@tcad.polito.it

Managing Editor
Jaqueline Zelkowitz
tcsvt@tcad.polito.it