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Sliding adjustment for 3D video representation

EURASIP JOURNAL ON APPLIED SIGNAL PROCESSING 2002年第10期2002卷 1088-1101页

作者： Galpin, F Morin, L Univ Rennes 1 IRISA INRIA Rennes F-35042 Rennes France

This paper deals with video coding of static scenes viewed by a moving camera. We propose an automatic way to encode such video sequences using several 3D models. Contrary to prior art in model-based coding where 3D models have to be known, the 3D models are automatically computed from the original video sequence. We show that several independent 3D models provide the same functionalities as one single 3D model, and avoid some drawbacks of the previous approaches. To achieve this goal we propose a novel algorithm of sliding adjustment, which ensures consistency of successive 3D models. The paper presents a method to automatically extract the set of 3D models and associate camera positions. The obtained representation can be used for reconstructing the original sequence, or virtual ones. It also enables 3D functionalities such as synthetic object insertion, lightning modification, or stereoscopic visualization. Results on real video sequences are presented.

关键词： sliding adjustment 3D model reconstruction video coding model-based coding video manipulation

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Real-time estimation of long-term 3-D motion parameters for SNHC face animation and model-based coding applications

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1999年第2期9卷 255-263页

作者： Smolic, A Makai, B Sikora, T Heinrich Hertz Inst Commun Technol D-10587 Berlin Germany

In this paper, we present two recursive methods for the real-time estimation of long-term three-dimensional (3-D) motion parameters from monocular image sequences suitable for synthetic/natural hybrid coding face animation and model-based coding applications. based on feature point extractions in every frame, the 3-D motion parameters of a human face are estimated with a predictive approach,The first method uses a recursive linear least squares approach and the second employs a nonlinear extended Kalman filter, which does not rely on a linearized model of the face motion. Both methods perform a prediction and correction loop at every time step. Compared to other methods described in the literature, the recursive and predictive structure of the proposed estimation process solves the problem of error accumulation in long-term motion estimation, This makes the estimation stable and consistent over long periods. Experimental results are presented for synthetic data and real image sequences, which demonstrate the performance of the estimation methods and compare the two approaches.

关键词： extended Kalman filter face animation long-term motion estimation model-based coding three-dimensional modeling

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Integrating active face tracking with model based coding

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PATTERN RECOGNITION LETTERS 1999年第6期20卷 651-657页

作者： Yin, LJ Basu, A Univ Alberta Dept Comp Sci Edmonton AB T6G 2H1 Canada

In this paper, input from an active camera is used for MPEG4 model based coding. First, the background is compensated considering a moving camera (tilt or pan). Second, the talking face is segmented from the compensated background using frame differences fusion. A morphological filter is then applied to make the system less sensitive to noise. Third, Hough Transform and deformable template coupled with color information are exploited to detect the facial features, e.g., eyes, mouth. Fourth, a wireframe model is adapted to the extracted face. The feasibility of the proposed system is demonstrated using a real active video sequence. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： active tracking MPEG-4 model-based coding feature detection

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Smoothing algorithms for clip-and-paste model-based video coding

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IEEE TRANSACTIONS ON CONSUMER ELECTRONICS 1999年第2期45卷 427-435页

作者： Hao, SS Lee, MF Yang, JF Natl Cheng Kung Univ Dept Elect Engn Tainan 701 Taiwan

model-based video coding has been adopted as a core experiment in ISO MPEG-4 standard. The clip-and-paste technique for putting video objects in line is an important tool to reduce the transmission rate. To assist the clip-and-pasting method fitting into the 2-D model, we propose several smoothing algorithms for improving the quality of the reconstructed images. In this paper, the proposed smoothing algorithms can adjust deformations of zoom, tilt, and rotation object images. Luminance smoothing algorithm is also applied to compensate the light source variations. Simulation results show that the smoothing methods help to improve clip-and-paste images to achieve a satisfactory quality in visual perceptions.

关键词： model-based coding clip-and-paste method smoothing algorithm

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CBIT - Context-based image transmission

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IEEE TRANSACTIONS ON INFORMATION TECHNOLOGY IN BIOMEDICINE 2001年第2期5卷 159-170页

作者： Salous, MN Pycock, D Cruickshank, GS Univ Birmingham Sch Elect & Elect Engn Birmingham B15 2TT W Midlands England Queen Elizabeth Hosp Dept Neurosurg Birmingham B15 2TH W Midlands England

Few networks offer sufficient bandwidth for the transmission of high resolution two- and three-dimensional medical image sets without incurring significant latency. Traditional compression methods achieve bit-rate reduction based on pixel statistics and ignore visual cues that are important in identifying visually informative regions. This paper describes an approach to managing image transmission in which spatial regions are selected and prioritized for transmission so that visually informative data is received in a timely manner. This context-based image transmission (CBIT) scheme is a lossless form of progressive image transmission (PIT) in which gross structure, represented by an approximate iconic image, is transmitted first. Each part of this iconic image is progressively updated, using a simple set of rules that take into account viewing requirements. CBIT is realized using knowledge about image composition to segment, label, prioritize, and fit geometric models to regions of an image. Tests, using neurological images, show that, with CBIT, a valuable transmitted image is received with a latency that is about one-tenth that of traditional PIT schemes. Frequently, the necessary regions of the image are transmitted in about half the time taken to transmit the full image.

关键词： knowledge-based segmentation model-based coding progressive image transmission teleradiology

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Modified Hough transforms for object feature extraction

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JOURNAL OF INFORMATION SCIENCE AND ENGINEERING 2001年第1期17卷 133-145页

作者： Yang, JF Hao, SS Natl Cheng Kung Univ Dept Elect Engn Tainan 701 Taiwan

In this paper, we propose the use of modified Hough transforms to efficiently extract object feature parameters, which are usually contaminated by heavily noisy corrugation and discontinuity. The modified HT (MHT) is developed by introducing spatial and parameter weighting functions to improve the detection performance for the traditional Hough transform (HT), which generally fails to robustly detect natural object parameters. Using designed test patterns and real images, simulations show that the proposed weighting functions are helpful in detecting noise-corrupted object features. Due to its robustness, the MHT can be easily figured with a coarse-re-fine adaptive search mechanism to reduce the huge amount of computation for feature parameters extraction.

关键词： modified Hough transform model-based coding feature parameters extraction coarse-to-fine search facial object estimation

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A new approach to wire-frame tracking for semantic model-based moving image coding

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SIGNAL PROCESSING-IMAGE COMMUNICATION 2000年第6期15卷 567-580页

作者： Antoszczyszyn, PM Hannah, JM Grant, PM Univ Edinburgh Dept Elect Engn Edinburgh EH9 3JL Midlothian Scotland

Automatic wire-frame fitting and automatic wire-frame tracking are the two most important and most difficult issues associated with semantic-based moving image coding. A novel approach to high-speed tracking of important facial features is presented as a part of a complete fitting-tracking system we have developed. The method allows real-time processing of head-and-shoulders sequences using software tools only. The algorithm is based on eigenvalue decomposition of the sub-images extracted from subsequent frames of the Video sequence. Since each facial feature (the left eye, the right eye, the nose and the lips) is tracked separately, the algorithm can be easily adapted for a parellel machine. The algorithm was tested on numerous widely used head-and-shoulders video sequences containing speaker's head pan, rotation and zoom with remarkably good results. The experiments we have carried out prove that it is possible to maintain tracking even when the facial features are partially occluded. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： tracking image coding semantic coding model-based coding wire-frame model principal components analysis

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model-aided coding: A new approach to incorporate facial animation into motion-compensated video coding

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2000年第3期10卷 344-358页

作者： Eisert, P Wiegand, T Girod, B Univ Erlangen Nurnberg Telecommun Lab D-91058 Erlangen Germany

We show that traditional waveform coding and 3-D model-based coding are not competing alternatives, but should be combined to support and complement each other. Both approaches are combined such that the generality of waveform coding and the efficiency of 3-D model-based coding are available where needed. The combination is achieved by providing the block-based video coder with a second reference frame for prediction, which is synthesized by the model-based coder. The model-based coder uses a parameterized 3-D head model, specifying shape and color of a person. We therefore restrict our investigations to typical videotelephony scenarios that show head-and-shoulder scenes. Motion and deformation of the 3-D head model constitute facial expressions which are represented by facial animation parameters (FAP's) based on the MPEG-4 standard. An intensity gradient based approach that exploits the 3-D model information is used to estimate the FAP's, as well as illumination parameters, that describe changes of the brightness in the scene. model failures and objects that are not known at the decoder are handled by standard block-based motion-compensated prediction, which is not restricted to a special scene content, but results in lower coding efficiency. A Lagrangian approach is employed to determine the most efficient prediction for each block from either the synthesized model frame or the previous decoded frame. Experiments on five video sequences show that bit-rate savings of about 35% are achieved at equal average peak signal-to-noise ratio (PSNR) when comparing the model-aided codec to TMN-10, the state-of-the-art test model of the H.263 standard. This corresponds to a gain of 2-3 dB in PSNR when encoding at the same average bit rate.

关键词： facial animation model-aided coding model-based coding multiframe prediction

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Global motion estimation in model-based image coding by tracking three-dimensional contour feature points

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1998年第2期8卷 181-190页

作者： Pei, SC Ko, CW Su, MS Natl Taiwan Univ Dept Elect Engn Taipei 10764 Taiwan

Recently a new type of video coding method called model-based image coding has attracted much attention as a potential candidate for low bit-rate visual communication services, This technique reconstructs the facial image with a preknown three-dimensional (3-D) human face model and its received model motion parameters, The parameters of the head motion are mainly divided into two parts: global motion parameters describe the rigid movement of the head, such as rotation and translation, and local motion parameters which deal with the nonrigid movements of facial expressions, such as the opening and closing of the mouth and eyes. In this paper, we propose a new approach which can estimate the head global motion more robustly and accurately, Comparing with the existing techniques to match only a few key points, here we extract 3-D contour feature points and use chamfer distance matching to estimate head global motion, This can improve and enhance the contour tracking performance greatly. We also develop another technique called facial normalization transform, It maps the facial region of the current input frame back to the normalized pose of the initial frame, Using this transform, we can analyze facial expressions at the same orientation and fixed region, This simplifies the analysis work a lot, Then, we do our encoding by the clip-and-paste method along with adaptive codebook technique. In the following, the coder and decoder system are briefly described, Since we mainly focus the work on the analysis and synthesis of the facial portion images, background analysis and bitstream coding technique will not be discussed in this paper.

关键词： contour feature points generic facial model global motion estimation model-based coding

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3D object articulation and motion estimation in model-based stereoscopic videoconference image sequence analysis and coding

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SIGNAL PROCESSING-IMAGE COMMUNICATION 1999年第10期14卷 817-840页

作者： Tzovaras, D Kompatsiaris, I Strintzis, MG Aristotelian Univ Salonika Dept Elect & Comp Engn Informat Proc Lab GR-54006 Salonika Greece

This paper describes a procedure for model-based analysis and coding of both left and right channels of a stereoscopic image sequence. The proposed scheme starts with a hierarchical dynamic programming technique for matching across the epipolar line for efficient disparity/depth estimation. Foreground/background segmentation is initially based on depth estimation and is improved using motion and luminance information. The model is initialised by the adaptation of a wireframe model to the consistent depth information. Robust classification techniques are then used to obtain an articulated description of the foreground of the scene (head, neck, shoulders). The object articulation procedure is based on a novel scheme for the segmentation of the rigid 3D motion fields of the triangle patches of the 3D model object. Spatial neighbourhood constraints are used to improve the reliability of the original triangle motion estimation. The motion estimation and motion field segmentation procedures are repeated iteratively until a satisfactory object articulation emerges. The rigid 3D motion is then re-computed for each sub-object and finally, a novel technique is used to estimate flexible motion of the nodes of the wireframe from the rigid 3D motion vectors computed for the wireframe triangles containing each specific node. The performance of the resulting analysis and compression method is evaluated experimentally. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： stereoscopic image sequence analysis model-based coding object articulation non-rigid 3D motion estimation

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