一种基于MPEG-4的感兴趣区域视频编码新方法

本文提出了一种基于MPEG-4的感兴趣区域视频编码新方法.通过对感兴趣区边沿宏块采用强制帧内编码及宏块内预测编码时参考位置的自适应选择,该方法有效地抑制了数据噪声的扩散和传播.通过采用自适应宏块大小的运动估计/补偿算法,提高了感兴趣区特别是图像运动复杂的感兴趣区的编码效率及质量.在码率分配部分,本文方法通过计算不同区域的图像复杂性和能量,依据用户可设定的感兴趣权重因子不等重地分配可用码率资源.实验证明,本文方法较大程度改善了感兴趣区视频编码的压缩效率,提高了码率分配地灵活性和有效性.     

基于感兴趣区的图像编码与渐进传输

本文采用一种任意形状的整型或非整型小波变换,结合高效的SPIHT(Set Partitioning In Hierarchical Trees)图像编码算法,分别实现了任意形状感兴趣区的无损压缩和非感兴趣的有损压缩算法.另外本文还提出了两种感兴趣区优先编码策略,可以保证在极低的码率下感兴趣区的重建质量远远好于非感兴趣区的重建质量,满足用户快速、个性化的浏览需求.这些方法得到的压缩码流都具有嵌入的特点,支持渐进传输.     

面向人在回路感兴趣区动态编码方法

针对人在回路中感兴趣区ROI（regions of interest）编码问题,提出了一种感兴趣区动态编码方法,该方法利用率失真函数凸函数特性,对处于相同编码层ROI、BG区域分别设定不同目标码率,在各编码层控制ROI和背景区码率,使得ROI获得比较高的编码质量,并允许在编码过程中任意指定、修改感兴趣区域及其优先级,实...     

基于兴趣区域的H.264/AVC会话视频传输算法

针对会话视频的严格的实时性要求,提出一种基于H.264/AVC会话视频的错误抵抗编方法;建立一种低复杂度的感兴趣区域分割算法;基于所提分割算法,对感兴趣区域进行长期参考帧预测编码,从而达到提高感兴趣区域的视频传输质量的目标.所提方法具有低复杂度的特点,能够满足会话视频的实时性要求,并且易于移植入H.264/AVC编码器.仿真结果证明了算法的鲁棒性和编码有效性.     

基于JPEG2000的动态多感兴趣区域编码新方法

提出了一种基于JPEG2000的动态多感兴趣区域编码新方法,可以广泛地应用于各种交互式的客户/服务器应用环境.通过利用空信息包的特性和LRCP渐进方式,服务器在无需重新编码的前提下完成了原始码流的重组,从而实现了在渐进传输过程中的任意时刻,均可以有效地满足客户动态定义感兴趣区域及改变各个感兴趣区域优先级的需求.同时,由于和原始的JPEG2000码流结构保持完全一致,利用该算法同样可以实现感兴趣区域或整幅图像的无损压缩编码及渐进传输.实验结果表明:所提算法具有高度的灵活性,可以实现在低运算需求时的快速编解码.     

面聚类网格简化新算法

三维物体表面重建广泛采用三角网格方法,密集的数据采样可以重建出精确的三维表面,但是庞大的数据量不利于多分辨率三维实时显示和三维物体网络传输,因此三维表面网格简化是迫切需要解决的问题之一.近年来表面简化问题得到了广泛地研究.本文提出基于面聚类的网格简化新算法,通过最小化最大类内距离算法进行面聚类实现区域划分,然后提取区域特征,进而根据特征点和边对区域进行受限三角剖分.实验说明本文提出的面聚类网格简化算法在保持三维表面几何拓扑特征的基础上取得了很好的简化效果.     

MPEG-4中基于DT网格编码算法的实现

本文按照MPEG-4标准对DT网格对象编码的要求,设计了一套完整的基于DT网格的编码算法.首先提出了网格对象编码的系统框架.在此基础上,着重研究了网格运动编码,提出了一种新的三角形运动连续预测方法及相应的残差图像处理方法.最后,对整个数据结构进行转换,使之完全按照标准规定的顺序进行编码.本文算法同H.263进行了全面的比较.结果表明,DT作为MPEG-4标准中的一种编码方法,有一定的实用价值.     

基于JNDD模型面向虚拟视绘制的快速深度图编码

为降低深度数据的编码复杂度并保证重建虚拟视点的质量,提出了一种基于JNDD模型面向虚拟视点绘制的快速深度图编码算法,引入最小可觉深度差模型,将深度图划分为对绘制失真敏感的竖直边缘区域与失真难以被人眼察觉的平坦区域,并相应地为编码过程中的宏块模式选择设计了两种搜索策略。实验结果表明,与JM编码方案相比,本文所提出的方法在保证虚拟视质量与编码码率基本不变的前提下,显著降低了编码复杂度,有助于在三维视频系统中提高深度编码模块的编码速度。     

红外图像中基于似物性与稀疏编码的行人检测

行人检测是计算机视觉的经典问题。针对红外图像中的行人检测问题,提出了一种基于似物性和稀疏编码及空间金字塔特征提取的行人检测方法。首先,针对红外图像的特点,利用基于频域残差的显著性分析方法得到红外图像的显著图,在此基础上提出了一种似物性计算方法,进而得到不同区域的似物度得分,并根据得分提取出感兴趣区域;其次,以尺度不变特征转换为基础,将稀疏编码和空间金字塔算法应用于非监督特征学习实现对感兴趣区域的特征提取;最后,利用线性支持向量机构建分类器实现对图像中每个感兴趣区域的行人检测。实验结果验证了本文提出的感兴趣区域提取算法和针对单幅红外图像行人检测算法的有效性。     

一种基于分类矢量量化器的小目标红外图像压缩方法

本文提出了一种基于分类矢量量化器的小目标红外图像的压缩方法。首先利用图像子块的平均灰度与纹理能量这两个参数将图像划分为背景区域与感兴趣区域,然后分别对两类区域的子块进行码书设计,用相对较多的码字描述感兴趣区域,用相对较少的码字描述背景区域,这样既达到了较高的压缩比,同时又较好的保留了感兴趣区域的信息,并且编码计算量有大幅度的下降。文中对分类矢量量化器对于减小编码计算量的作用进行了理论分析。实验结果表明在相同码书尺寸的情况下本算法比直接矢量量化方法更好地保留了红外图像中的小目标信息,并且加快了编码速度。     

Scalable intraband wavelet‐based coding scheme for irregular meshes

This paper describes a novel scalable 3D triangular mesh coding method based on wavelet transform and successive approximation quantization. The algorithm efficiently exploits the intracorrelations between wavelet coefficients independently in each subband. Non‐significant wavelet coefficients are clustered, in a per bit‐plane manner, by using an octree‐based approach. An hierarchical bitstream is then generated allowing to gradually decode the 3D mesh at the desired quality or resolution representation. Our proposal can be executed on arbitrary topology meshes by using irregular wavelet decomposition. Objective and subjective quality evaluation on representative 3D meshes shows that the proposed codec provides competitive compression results when compared to the state‐of‐the‐art. Furthermore, it fits well to applications that require fast interactive handling of highly detailed 3D meshes, over networks with limited and/or variable bandwidth.     

Rate-distortion-optimized predictive compression of dynamic 3D mesh sequences

Compression of computer graphics data such as static and dynamic 3D meshes has received significant attention in recent years, since new applications require transmission over channels and storage on media with limited capacity. This includes pure graphics applications (virtual reality, games) as well as 3DTV and free viewpoint video. Efficient compression algorithms have been developed first for static 3D meshes, and later for dynamic 3D meshes and animations. Standard formats are available for instance in MPEG-4 3D mesh compression for static meshes, and Interpolator Compression for the animation part. For some important types of 3D objects, e.g. human head or body models, facial and body animation parameters have been introduced. Recent results for compression of general dynamic meshes have shown that the statistical dependencies within a mesh sequence can be exploited well by predictive coding approaches. Coders introduced so far use experimentally determined or heuristic thresholds for tuning the algorithms. In video coding, rate-distortion (RD) optimization is often used to avoid fixed thresholds and to select the optimum prediction mode. We applied these ideas and present here an RD-optimized dynamic 3D mesh coder. It includes different prediction modes as well as an RD cost computation that controls the mode selection across all possible spatial partitions of a mesh to find the clustering structure together with the associated prediction modes. The general coding structure is derived from statistical analysis of mesh sequences and exploits temporal as well as spatial mesh dependencies. To evaluate the coding efficiency of the developed coder, comparative coding results for mesh sequences at different resolutions were carried out.     

三维图像的任意形状ROI小波零块压缩编码算法

感兴趣区(ROI)编码是在JPEG2000中提出的一种重要的技术,然而JPEG2000算法却无法同时支持任意形状ROI和任意提升因子.本文提出了一种基于任意形状ROI和3D提升小波零块编码的3D体数据图像压缩算法.新的算法支持ROI内外从有损到无损的编码.一种简单的任意形状无损ROI掩码(Mask)生成方法被提出.考虑到3D子带的特点,我们采用改进的3DSPECK零块算法对变换后的系数进行编码.一些其它支持任意形状ROI编码的算法也在本文中被评估,试验显示本文算法具有更好的编码性能.     

Objective and subjective evaluation of static 3D mesh compression

3D mesh compression is essential in the context of network-based virtual worlds, but so are objective and subjective fidelity of the reconstructed mesh to the original one. Unfortunately, it is difficult to establish a fair way to compare objectively two textured, triangular 3D meshes meant to approximate the surface of the same 3D object. We explain why by elaborating on how the geometric distance between two meshes can be estimated, after introducing some basic concepts related to mesh shape and a brief taxonomy of static 3D mesh coding techniques. We review a selection of such coding techniques, almost all of which deal only with the shape of the surface, and then focus on surface appearance, usually described separately with a texture to be mapped onto the 3D mesh at rendering time, and we also review existing techniques specifically devised to compress textures meant for 3D models. Finally, we discuss the even larger complexity of establishing any reasonable way to compare the subjective quality of the experience produced by two versions of the same 3D object, especially if different rendering methods may be used.     

一种基于立体视觉显著性的多视点视频比特分配方法

针对多视点立体视频压缩编码,提出了一种基于立 体视觉显著性的比 特分配方法。研究综合利用多视点立体视频数据中场景的运动、深度以及深度边缘信息提取 人眼感兴趣区 域(ROI)的方法;然后根据ROI的划分结果优化区域比特分配。实验结果表 明,本文提出的算法能有效提 高ROI区域的编码性能,同时整体视频的率失真性能有一定程度的提高。     

Technologies for 3D mesh compression: A survey

Three-dimensional (3D) meshes have been widely used in graphic applications for the representation of 3D objects. They often require a huge amount of data for storage and/or transmission in the raw data format. Since most applications demand compact storage, fast transmission, and efficient processing of 3D meshes, many algorithms have been proposed to compress 3D meshes efficiently since early 1990s. In this survey paper, we examine 3D mesh compression technologies developed over the last decade, with the main focus on triangular mesh compression technologies. In this effort, we classify various algorithms into classes, describe main ideas behind each class, and compare the advantages and shortcomings of the algorithms in each class. Finally, we address some trends in the 3D mesh compression technology development.     

Segmentation-based compression scheme for 3D animated models

This paper presents an efficient compression algorithm for animated three-dimensional (3D) meshes. First, a segmentation approach is applied to achieve the motion estimation. The main idea is to exploit the temporal coherence of the geometry component by using the heat diffusion properties. The motion of the resulting regions is accurately described by 3D affine transforms. These transforms are computed at the first frame to match the subsequent ones. Second, in order to achieve a good compression performance, an efficient rate control mechanism is proposed to quantize the temporal prediction errors. At this stage, a rate-distortion model is used for quantizing the residual information. Comparative coding tests, for irregular 3D mesh sequences, were conducted to evaluate the coding efficiency of the proposed compression scheme. Simulation results show very promising performances.     

Fast 3D Mesh Compression Using Shared Vertex Analysis

A trend in 3D mesh compression is codec design with low computational complexity which preserves the input vertex and face order. However, this added information increases the complexity. We present a fast 3D mesh compression method that compresses the redundant shared vertex information between neighboring faces using simple first‐order differential coding followed by fast entropy coding with a fixed length prefix. Our algorithm is feasible for low complexity designs and maintains the order, which is now part of the MPEG‐4 scalable complexity 3D mesh compression standard. The proposed algorithm is 30 times faster than MPEG‐4 3D mesh coding extension.     

View-dependent 3-D mesh coding by rate allocation with the image rendering-based distortion measures

Low-bandwidth transmission of synthetic digital content to the end user device in the form of a scene of 3-D meshes requires efficient compression of the mesh geometry. For applications in which the meshes are observed from a single viewpoint, this work explores the use of the image rendering-based distortion measures in rate allocation to their surface regions for view-dependent mesh geometry compression. It is experimentally demonstrated that the image rendering-based distortion measures yield far superior performance (the quality of the rendered image of the reconstructed scene from a viewpoint at a given rate) in optimal rate allocation than other previously proposed distortion measures. A fast rate allocation method is also proposed for use with the image rendering-based measures for real-time or interactive applications. Not only does this method have significantly lower complexity than the optimal rate allocation method due to the rendering of the images of the reconstructed meshes at only judiciously selected rate–distortion operating points, but also its coding performance is just as competitive. Further complexity reduction in rate allocation, through rendering of only the coded regions of the meshes, is also investigated.