模型基编码中的运动估值研究

在介绍模型编码基本原理的基础上,着重介绍了语义基编码,对它的运动估值技术作了详细分析,并用光流法对运动图像进行了运动估值,对该估值算法作了评价和展望。     

模型基编码中的脸部运动估值研究

主要针对模型基编码方案的运动参数估值问题，运用3维运动估值的方法，推导出运用于人脸运动参数估值的运动模型和光流算法，并对该算法的效果进行分析，对算法的改进提出算法。     

部分均方误差模型及运动估值误差匹配新准则

在运动图象压缩编码研究中，运动估值的误差匹配过程与运动搜索过程同等重要，普遍采用的ＭＡＤ准则并不适于噪声环境和小波变换域，ＭＳＥ，高阶累积量等匹配准则效果较好，但由于运算量大，特别是存在众多乘法操作，所以它们很少被应用到实际系统中，本文对匹配过程的优化作了较深入的研究，在对匹配误差绝对值的分布特性作的统计实验的基础上，提出了部分均方误差的新模型，并运用模型对上述匹配准则进行优化，模型通过对误差特征     

区域基视频编码的基本方法及关键技术

介绍了一种区域基频编码的基本方法以及关键技术，这种编码方法适合于极低比特率的视频编码应用，包括时间递归形态分割，基于区域的运动估计以及采用运动补偿预测的轮廓－纹理编码。该编码方法是输入的图像序列内容没有任何限制，而且其算法结构可按不同的图像质量等级和比特率要求实现可分级的编码过程。     

脸部序列图像的模型基编码

本文以头部线框模型和图像处理、模式识别、计算机图形学技术为基础，提出了一套完整的会议电视头肩序列图像的分析—综合模型。在低于６４ｋｂｉｔ／ｓ的码率下，得到主观质量很高的图像。     

运动图像的压缩编码技术

1　概述国际标准化组织于 1988年成立了一个致力于制定有关运动图像压缩编码的组织ＭＰＥＧ (ＭｏｖｉｎｇＰｉｃ ｔｕｒｅＥｘｐｅｒｔｓｇｒｏｕｐ) ,意思是“运动图像专家组”。这个专家组的任务是给用于数字存储介质、电视广播和通信的运动图像和它的伴音制定一种通用的编码方法。ＭＰＥＧ组织在工作一开始就考虑到相关标准化组织的研究成果 ,如ＪＰＥＧ和Ｈ .2 6 1标准。运动图像可以看成是静止图像的一个序列 ,所以运动图像的帧内编码技术就采用了ＪＰＥＧ推荐的离散余弦变换ＤＣＴ技术。此外ＭＰＥＧ又加进了帧间压缩编码技术。 1992…     

模型基图像编码

本文扼要综述模型基图像编码中两类方法(语义基和物体基)的最近成果。此外,还介绍了两种新的可视通信系统(虚拟空间会议电视和电视呈现系统)之构想。     

用于DT网格模型基视频编码的三角形分割准则

在分析DT(Delaunay tdangulation)网格已有的2种分割准则--灰度误差最小化准则和灰度分布均匀化准则在网格基编码不足的基础上,提出了一种新的DT网格分割准则--灰度误差平方和最小化准则,使三角形分割更加合理有效,编码性能比以前的方法有明显提高.在此基础上提出了帧内变换编码/帧间网格基运动估计的混合编码方案,该方案可应用于复杂运动和背景的视频序列中,突破了以往模型基编码只能应用于视频会议的限制.实验结果表明,该编码方案在复杂运动和背景的应用场合高出了H.263的编码性能.     

模型基辅助编码中实时运动估计的自适应方法

在长序列运动估计中,常用的预测最小均方力法(PLS、MPLS)和扩展的卡尔曼滤波方法(EKF)对误差敏感,鲁棒性差。本文提出一种新的自适应实时三维运动估计方法(MEKF):即设计一个实时自适应调整参数的扩展卡尔曼滤波进行运动估计,然后对其经过数据处理,消除估计的振荡误差。文中还将该方法与前三种估计方法进行了模拟和真实序列实验的对比,实验结果表明本文所提出的估计方法具有很好的稳定性利很高的精度。     

模型基编码中脸部模型的自动调整

通用模型的调整是模型基人脸图像编码的重要步骤,本文提出了一种利用改进的变形模板提取脸部完整特征、由径向基函数内插调整模型非特征点的正面脸部模型自动调整算法.首先用矩形模板匹配确定各特征区域,模板尺寸由先验知识设计;在各特征区域内确定变形模板的初始位置和变化范围,采用遗传算法等匹配方式,获取变形模板的最优参数值;最后估计输入人脸姿态,进行模型的全局变换和用径向基函数内插调整模型非特征点,得到输入人脸的特定模型.实验结果表明,对于输入为简单背景的肩头像,该算法简便快速,可获得较好的调整效果.     

Three-dimensional parameter estimation from stereo image sequences for model-based image coding

It is shown that the analysis of moving image sequences for 3D modelling can be performed in a relatively straightforward manner if the scene is captured in stereo. Output from a stereo disparity estimation process using calibrated cameras gives absolute 3D surface coordinates from a single stereo pair. When combined with monocular motion cues, the true 3D motion parameters of moving objects can be accurately calculated. Further analysis enables segmentation of body elements according to motion while the 3D surface feature structure, although available from the start, can be integrated and checked for anomalies over the sequence. These results are expected to alleviate the known problems of ambiguity suffered by monocular-source model-based coders.     

Texture mapping in model-based image coding

An analysis is given of texture storage and reprojection as used in model-based image coding. It is shown that changes in object surface orientation give rise to combined amplitude and frequency modulation of the surface texture when projected onto the image plane. When stored texture is reprojected onto a model, inaccuracies in the model shape cause texture displacements under rotational motion. The use of these results to improve model-based prediction in practical systems is discussed.     

三角形网格基活动图像编码研究——运动估计、运动补偿和残差图像处理

本文深入讨论了三角形网格基（包括DTM和RTM）的活动图像编码方法，包括帧间运动预测及残差图像处理方法等。其中主要涉及三角形网格的分割方法，运动矢量计算和优化方法。实验结果表明，三角形网格基运动补偿比传统的矩形匹配BMA方法有更好的主客观质量。     

帧差预测3D-DCT子带分层编码的研究

本文提出了一种利用３Ｄ－ＤＣＴ帧差预测变换域频率系数进行了带划分的分层编码方法。与其它变换系数分层编码相比,３Ｄ－ＤＣＴ变换编码概念的引入,使该方法可以在实现空间方向分层的同时,实现时间方向分层。另外,它比采用时间方向亚抽样和空间滤波器的分辨率分层方法更灵活,并克服了频率混叠现象。该方法可用于实现分层图像通信,适合未通信发展的需要。     

Speed-up trend analysis for H.261 and model-based image coding algorithms using a parallel-pipeline model

Model-based and object-oriented coding algorithms are generally more computationally complex than current block-based image coding standards such as H.261, due primarily to the complexity of the image analysis they require. In this paper, simulations of H.261 and two model-based coding algorithms are analysed in terms of their computational complexity, and mapped onto a generalised image coder parallel-pipeline model. Example implementations of the H.261 coder and an object-oriented coder using general purpose parallel processor systems are then presented to confirm the validity of the performance trend analyses; these achieve maximum speedups of about 11 and 1.7, respectively, using up to 16 processors. The performance trends shown by the analysis indicate that the complexity of model-based coding algorithms, when combined with their reliance on coding picture differences and content-dependent algorithm execution times, interact to make it very difficult to achieve significant speed-up of sequential algorithms. Furthermore, the algorithm complexity and abstract data structures will make direct hardware implementations increasingly difficult. Overcoming these problems to achieve real-time model-based coders may require significant algorithmic compromises to be made.     

Joint video/depth rate allocation for 3D video coding based on view synthesis distortion model

Joint video/depth rate allocation is an important optimization problem in 3D video coding. To address this problem, this paper proposes a distortion model to evaluate the synthesized view without access to the captured original view. The proposed distortion model is an additive model that accounts for the video-coding-induced distortion and the depth-quantization-induced distortion, as well as the inherent geometry distortion. Depth-quantization-induced distortion not only considers the warping error distortion, which is described by a piecewise linear model with the video power spectral property, but also takes into account the warping error correlation distortion between two sources reference views. Geometry distortion is approximated from that of the adjacent view synthesis. Based on the proposed distortion model, a joint rate allocation method is proposed to seek the optimal trade-off between video bit-rate and depth bit-rate for maximizing the view synthesis quality. Experimental results show that the proposed distortion model is capable of approximately estimating the actual distortion for the synthesized view, and that the proposed rate allocation method can almost achieve the identical rate allocation performance as the full-search method at less computational cost. Moreover, the proposed rate allocation method consumes less computational cost than the hierarchical-search method at high bit-rates while providing almost the equivalent rate allocation performance.     

Model-based analysis synthesis image coding (MBASIC) system for a person's face

The initial conception of a model-based analysis synthesis image coding (MBASIC) system is described and a construction method for a three-dimensional (3-D) facial model that includes synthesis methods for facial expressions is presented. The proposed MBASIC system is an image coding method that utilizes a 3-D model of the object which is to be reproduced. An input image is first analyzed and an output image using the 3-D model is then synthesized. A very low bit rate image transmission can be realized because the encoder sends only the required analysis parameters. Output images can be reconstructed without the noise corruption that reduces naturalness because the decoder synthesizes images from a similar 3-D model.

In order to construct a 3-D model of a person's face, a method is developed which uses a 3-D wire frame face model. A full-face image is then projected onto this wire frame model. For the synthesis of facial expressions two different methods are proposed; a clip-and-paste method and a facial structure deformation method.     

Estimation of point light source parameters for object-based coding

In this paper, the source model of moving rigid 3D objects of an object-based analysis-synthesis coder (OBASC) is extended from diffuse to non-diffuse illumination introducing the explicit illumination model of a distant point light source and ambient diffuse light. For each image of a real image sequence containing moving objects, first, shape and 3D motion parameters describing the objects are estimated assuming an ellipsoid-like smooth shape. Then, the illumination parameters are estimated by a fast iterative maximum-likelihood Gauβ-Newton estimation method. Typically, the illumination parameters converge after very few images close to the true ones. The accurateness depends on the amount of object rotation and the correctness of the shape assumptions. For a real image sequence showing a textured ball covering 20% of image area, rotating about 10 ° per frame, and illuminated by spot and ambient light, the extension of the source model reduces the model failures from 9.9% of the image area to 6.7%. In the area of model failures, the image synthesized from the source model parameters differ significantly from the real image. In this early experiment, source model parameters are coded losslessly. Since model failures are expensive by means of bit-rate, a significant reduction of bit-rate can be expected.