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IEEE International Conference on Image Processing (ICIP 2006)

作者： Artigas, Xavi Torres, Luis Tech Univ Catalonia Barcelona Spain

ISBN: (纸本)9781424404810

Distributed Source coding (DSC), formulated thirty years ago, is lately witnessing a great research effort. This effort is encouraged by emerging new applications that could greatly benefit from the properties inherent to DSC, like low complexity encoders and embedded error resilience. Among the challenging topics related to DSC there is the generation of the Side Information, an estimation made by the decoder of the information being decoded. This paper quickly summarizes the theoretical bases of DSC and then focuses on the essential task of generating the Side Information, by developing the model-based method drafted by the authors on a previous publication. It is shown that the application of model-based Side Information generation techniques on top of current state of the art DSC-based video codecs provides an improvement of 0.5 to 0.75dB over a wide range of bit-rates. Comparisons against H.264 are also provided.

关键词： distributed video coding Wyner-Ziv coding side information model-based coding

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The clustered causal state algorithm - Efficient pattern discovery for lossy data-compression applications

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COMPUTING IN SCIENCE & ENGINEERING 2006年第5期8卷 59-67页

作者： Schmiedekamp, Mendel Subbu, Aparna Puoha, Shashi Penn State Univ Intelligent Control Dept Informat Sci & Technol Div Appl Res Lab University Pk PA 16802 USA

Pattern discovery is a potential boon for data compression, but current approaches are inefficient and produce cumbersome pattern descriptions. The clustered causal state algorithm is a new pattern-discovery algorithm... 详细信息

关键词： clustering model-based coding pattern analysis real-time systems statistical pattern models clustering model-based coding pattern analysis real-time systems statistical pattern models

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Tracking a detected face with dynamic programming

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IMAGE AND VISION COMPUTING 2006年第6期24卷 573-580页

作者： Yao, Zhengrong Li, Haibo Umea Univ Digital Media Lab S-90187 Umea Sweden

In this paper, we consider the problem of tracking a Moving human face in front of a video camera in real-time for a model-based coding application. The 3D head tracking in a MBC system could be implemented sequentially as 2D location tracking, coarse 3D orientation estimation and accurate 3D motion estimation. This work focuses on the 2D location tracking of one face object through continuously using a face detector. The face detection scheme is based on a boosted cascade of simple Haar-like feature classifiers. Although such a detector demonstrated rapid processing speed, high detection rate can only be achieved for rather strictly near front faces. This introduces the 'loss of tracking' problem when used in 2D tracking. This paper suggests an easy method of solving the pose problem by using the technique of Dynamic Programming. The Haar-like facial features used in the 2D face detector are spatially arranged into a 1D deformable face graph and the Dynamic Programming matching is used to handle the 'loss of track' problem. Dynamic Programming matches the deformed version of the face graph extracted from a rotated face with the template taken online before 'loss of tracking' happens. Since the deformable face graph covers a big pose variation, the developed technique is robust in tracking rotated faces. Embedding Haar-like facial features into a deformable face graph is the key feature Of Our tracking scheme. A real time tracking system based on this technique has been set tip and tested. Encouraging results have been got and are reported. (c) 2005 Elsevier B.V. All rights reserved.

关键词： model-based coding face tracking face detection Dynamic Programming

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Geometry-assisted image-based rendering for facial analysis and synthesis

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SIGNAL PROCESSING-IMAGE COMMUNICATION 2006年第6期21卷 493-505页

作者： Eisert, Peter Rurainsky, Mrgen Heinrich Hertz Inst Nachrichtentech Berlin GmbH Fraunhofer Inst Telecommun D-10587 Berlin Germany

In this paper, we present an image-based method for the tracking and rendering of faces. We use the algorithm in an immersive video conferencing system where multiple participants are placed in a common virtual room. This requires viewpoint modification of dynamic objects. Since hair and uncovered areas are difficult to model by pure 3-D geometry-based warping, we add image-based rendering techniques to the system. By interpolating novel views from a 3-D image volume, natural looking results can be achieved. The image-based component is embedded into a geometry-based approach in order to limit the number of images that have to be stored initially for interpolation. Also temporally changing facial features are warped using the approximate geometry information. Both geometry and image cube data are jointly exploited in facial expression analysis and synthesis. (c) 2006 Elsevier B.V. All rights reserved.

关键词： facial animation image-based rendering model-based coding face tracking 3-D image analysis and synthesis

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Visual estimation and compression of facial motion parameters - Elements of a 3D model-based video coding system

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INTERNATIONAL JOURNAL OF COMPUTER VISION 2002年第2期50卷 111-125页

作者： Tao, H Huang, TS Univ Calif Santa Cruz Dept Comp Engn Santa Cruz CA 95064 USA Univ Illinois Beckman Inst Image Proc & Format Lab Urbana IL 61801 USA

The MPEG4 standard supports the transmission and composition of facial animation with natural video by including a facial animation parameter (FAP) set that is defined based on the study of minimal facial actions and is closely related to muscle actions. The FAP set enables model-based representation of natural or synthetic talking head sequences and allows intelligible visual reproduction of facial expressions, emotions, and speech pronunciations at the receiver. This paper describes two key components we have developed for building a model-based video coding system: (1) a method for estimating FAP parameters based on our previously proposed piecewise Bezier volume deformation model (PBVD), and (2) various methods for encoding FAP parameters. PBVD is a linear deformation model suitable for both the synthesis and the analysis of facial images. Each FAP parameter is a basis function in this model. Experimental results on PBVD-based animation, model-based tracking, and spatial-temporal compression of FAP parameters are demonstrated in this paper.

关键词： nonrigid motion analysis facial animation model-based coding MPEG4

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model-based global and local motion estimation for videoconference sequences

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2004年第9期14卷 1156-1161页

作者： Calvagno, G Fantozzi, F Rinaldo, R Viareggio, A Univ Padua Dipartimento Ingn Informaz I-35131 Padua Italy Univ Udine Dipartimento Ingn Elettr Gest & Meccan I-33100 Udine Italy

In this work, we present an algorithm for face 3-D motion estimation in videoconference sequences. The algorithm is able to estimate both the position of the face as an object in 3-D space (global motion) and the movements of portions of the face, like the mouth or the eyebrows (local motion). The algorithm uses a modified version of the standard 3-D face model CANDIDE. We present various techniques to increase robustness of the global motion estimation which is based on feature tracking and an extended Kalman filter. Global motion estimation is used as a starting point for local motion detection in the mouth and eyebrow areas. To this purpose, synthetic images of these areas (templates),are generated with texture mapping techniques, and then compared to the corresponding regions in the current frame. A set of parameters, called action unit vectors (AUVs) influences the shape of the synthetic mouth and eyebrows. The optimal AUV values are determined via a gradient-based minimization procedure of the error energy between the templates and the actual face areas. The proposed scheme is robust and was tested with success on sequences of many hundreds of frames.

关键词： adaptive Kalman filtering block matching eyebrow tracking face tracking feature tracking lip tracking model-based coding template matching

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model-based coding for multi-objects sequence

Model-based coding for multi-objects sequence

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Conference on Visual Communications and Image Processing 2001

作者： Liu, YH Yu, L Yao, QD Zhejiang Univ Inst Informat & Commun Engn Hangzhou 310027 Peoples R China

ISBN: (纸本)0819439886

model-based coding has been studied mostly on video sequence with only one person. Normally there are several persons in the videoconference scenes. In this paper, model-based coding for multi-objects (or multi-person) sequence is explored. A multi-scale 3D wire-frame of head has been constructed to fit for different head size on the scene. The object is composed of several components such as head, shoulder and arm. Wire-frame of shoulder and arm are built in this contribution, By connecting different components according to physical structure, a more complete wire-frame of upper body with head is built. The ways of motion parameters transferring through the different components are determined. The bit-rate of three-object sequence is compared with one-object sequence with the same image format. model-based coding efficiency of multi-object sequence is higher than that of one-object sequence.

关键词： model-based coding multi-objects 3D wire-frame 3D rigid motion videoconference

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Generating realistic facial expressions with wrinkles for model-based coding

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COMPUTER VISION AND IMAGE UNDERSTANDING 2001年第2期84卷 201-240页

作者： Yin, LJ Basu, A SUNY Binghamton Thomas J Watson Sch Engn & Appl Sci Dept Comp Sci Binghamton NY 13902 USA Univ Alberta Dept Comp Sci Edmonton AB T6G 2H1 Canada

Due to the limitations of current computer graphics technology mimicing realistic facial textures, such as wrinkles, is very difficult. Facial texture updating and compression are crucial to achieving realistic facial animation for low bit rate model-based coding. In this paper, we present a partial texture updating method for realistic facial expression synthesis with facial wrinkles. First, fiducial points on a face are estimated using a color-based deformable template matching method. Second, an extended dynamic mesh matching algorithm is developed for face tracking. Next, textures of interest (TOI) in the potential expressive wrinkles and mouth-eye texture areas are captured by the detected fiducial points. Among the TOI, the so-called active textures or expressive textures are extracted by exploring temporal correlation information. Finally, the entire facial texture is synthesized using the active texture. Compared to the entire texture updating scheme, partially updating and compressing facial textures significantly reduce the computational complexity and bit rates while still producing an acceptable visual quality. Experiments on the video sequences demonstrate the advantage of the proposed algorithm. (C) 2001 Elsevier Science (USA).

关键词： texture coding MPEG4 model-based coding feature detection SNHC

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Synthesizing realistic facial animations using energy minimization for model-based coding

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PATTERN RECOGNITION 2001年第11期34卷 2201-2213页

作者： Yin, LJ Basu, A Bernögger, S Pinz, A Univ Alberta Dept Comp Sci Edmonton AB T6G 2H1 Canada Graz Univ Technol Inst Comp Graph & Vis A-8010 Graz Austria

Accurate localization and tracking of facial features are crucial for developing high-quality model-based coding systems. In this paper we describe the integration of simple heuristics which are effective in improving the results of well-known facial feature detection with robust techniques for adapting a dynamic mesh for animation. A new method of generating a self-adaptive mesh using an extended dynamic mesh (EDM) is proposed to overcome the convergence problem of the dynamic-motion-equation method (DMM). The new method consisting of two-step mesh adaptation (called coarse-to-fine adaptation) can enhance the stability of the DMM and improve the performance of the adaptive process. The accuracy of the proposed approach is demonstrated by experiments on eye model animation. In this paper, we focus our discussion only on the detection, tracking, modeling and animation of eye movements. (C) 2001 Pattern Recognition Society. Published by Elsevier Science Ltd, All rights reserved.

关键词： eye-movement tracking facial animation energy minimization model-based coding SNHC

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Video coding of model-based at very low bit rates

Video coding of model-based at very low bit rates

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Conference on Visual Communications and Image Processing 2003

作者： Fu, XP Wang, Z Dalian Maritime Univ Dept Comp Sci & Technol Dalian 116026 Peoples R China

ISBN: (纸本)0819450235

Very low bit rate coding is an important part of the MPEG-4 standard. To obtain maximum compression in videoconference sequences a technique called model-based coding can be used. With this technique, the face of the speaker is represented by a model, and its movement between frames is coded with a small set of parameters. As with all MPEG standards, the encoder algorithm is not described and this leaves the door open to many possible implementations. In this paper, a summary of model-based coding is presented. Many fields have been studied, including 3D wire-frame models, face detection, facial feature extraction, motion parameter estimation, and face model parameter coding. Several problems need to be solved before model-based video communication will become practical. Some of them are discussed in this paper, such as how to detect and locate a face in an image, how to extract parameters from an image to adapt a face model, and how to compress the animation parameters.

关键词： videoconference model-based coding 3D wire-frame model face detection facial feature extraction motion parameter estimation face model parameter coding

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