Model-Based Power Aware Compression Algorithms for MPEG-4 Virtual Human Animation in Mobile Environments

MPEG-4 body animation parameters (BAP) are used for animation of MPEG-4 compliant virtual human-like characters. Distributed virtual reality applications and networked games on mobile computers require access to locally stored or streamed compressed BAP data. Existing MPEG-4 BAP compression techniques are inefficient for streaming, or storing, BAP data on mobile computers, because: 1) MPEG-4 compressed BAP data entails a significant number of CPU cycles, hence significant, unacceptable power consumption, for the purpose of decompression, 2) the lossy MPEG-4 technique of frame dropping to reduce network throughput during streaming leads to unacceptable animation degradation, and 3) lossy MPEG-4 compression does not exploit structural information in the virtual human model. In this article, we propose two novel algorithms for lossy compression of BAP data, termed as BAP-Indexing and BAP-Sparsing. We demonstrate how an efficient combination of the two algorithms results in a lower network bandwidth requirement and reduced power for data decompression at the client end when compared to MPEG-4 compression. The algorithm exploits the structural information in the virtual human model, thus maintaining visually acceptable quality of the resulting animation upon decompression. Consequently, the hybrid algorithm for BAP data compression is ideal for streaming of motion animation data to power- and network-constrained mobile computers     

Superimposed training for channel estimation of OFDM modulated amplify-and-forward relay networks

This paper is concerned with the problem of channel estimation for amplify-and-forward （AF） cooperative relay networks with orthogonal frequency division multiplexing （OFDM） modulation. The algorithm is based on both the least square （LS） and minimum mean square error （MMSE） technique with a superimposed training strategy. Specifically, both the source and relay superimpose their own training signal onto data stream prior to transmission so as to estimate the separate channel state information of the source to relay link and the relay to destination link. We also present the performance analysis and derive the approximated closed-form expressions for the MSE of separate channel estimation of source to relay link and the relay to destination link, respectively, from which we compute the optimal training signal as well as the relay power-amplification factor. To further improve the performance of channel estimation, we adopt a weighted average process to enhance the estimation performance over multiple OFDM blocks, from which we compute the optimal tracking factor. Simulation results are provided to corroborate the proposed scheme.     

A group of novel approaches and a toolkit for motion capture data reusing

Now more and more motion capture (MoCap) systems are used to acquire realistic and highly detailed motion data which are widely used for producing animations of human-like characters in a variety of applications, such as simulations, video games and animation films. And recently large MoCap databases are available. As a kind of emerging multimedia data, 3D human motion has its own specific data form and standard format. But to the best of our knowledge, only a few approaches have been explored for 3D MoCap data feature representation and reusing. This paper proposes a group of novel approaches for posture feature representation, motion sequence segmentation, key-frame extraction and content-based motion retrieval, which are all very important for MoCap data reusing and benefit to the efficient animation production. To validate these approaches, we set up a MoCap database and implemented a prototype toolkit. The experiments show that the proposed algorithms could achieve the approvable results.     

基于MPEG-4的人脸动画技术研究

MPEG-4提出的基于对象的编码格式，将人脸作为一个特殊的对象，为人脸建模和动画研究奠定了基础。本文通过对MPEG-4人脸动画标准的分析，提出基于MPEG-4人脸动画系统的设计思想和需解决的关键问题。     

视频压缩技术及其在远程教学系统中的应用

MPEG标准是一个优于其他压缩/解压缩方案的系列标准.其中MPEG-4标准以其低速率传输高质量画面的优势,在越来越多的领域内得以应用,成为近几年来的压缩标准的主流.主要介绍MPEG-4的特点和优势及其在远程教学系统中的应用.     

一种ARGB数据无损压缩解压算法的FPGA设计

提出了一种ARGB数据的无损压缩优化算法以及FPGA实现方法。为了避免对整个文件的解压和压缩,采用了Deflate算法的相关方法对图像按块进行压缩和解压,极大提高了存储器的访问效率。利用了Deflate算法对小块进行压缩,发挥了Deflate中LZ77压缩的Huffman压缩技术来优化压缩算法。通过VIVADO HLS将算法实现成FPGA电路,采用多张图片进行了实际应用,证实了算法的有效性,并分析了其功耗和时序信息。     

一种基于Linux的MPEG-4算法实现

MPEG-4是基于对象的多媒体数据压缩标准,广泛应用于远程监控等多媒体领域。本文介绍了MPEG-4编码标准,分析了MPEG-4算法的结构、流程,给出了一种基于Linux的MPEG-4算法的实现。     

基于数据结构化的三维动画压缩方法研究

在三维动画应用日益广泛的背景下,研究三维动画数据压缩方法对其数据的存储、传播和渲染技术至关重要.基于图像数据的结构化特征,计算机视觉领域提出了一系列高效图像压缩技术.鉴于三维动画数据与图像数据结构的差异,探讨三维动画数据结构化方法,进而探索改进图像算法以实现一种新的三维动画数据压缩方法.具体而言,首先研究对三维模型顶点...     

基于Kinect的人体姿态估计优化和动画生成

为了生成更准确流畅的虚拟人动画,采用Kinect设备捕获三维人体姿态数据的同时,使用单目人体三维姿态估计算法对Kinect的彩色信息进行骨骼点数据推理,从而实时优化人体姿态估计效果,并驱动虚拟人物模型生成动画。首先,提出了一种时空优化的骨骼点数据处理方法,以提高单目估计人体三维姿态的稳定性;其次,提出了一种Kinect和遮挡鲁棒姿势图（ORPM）算法融合的人体姿态估计方法来解决Kinect的遮挡问题;最后,研制了基于四元数向量插值和逆向运动学约束的虚拟人动画系统,其能够进行运动仿真和实时动画生成。与仅利用Kinect捕获人体运动来生成动画的方法相比,所提方法的人体姿态估计数据鲁棒性更强,具备一定的防遮挡能力,而与基于ORPM算法的动画生成方法相比,所提方法生成的动画在帧率上提高了两倍,效果更真实流畅。     

基于LeapMotion的个体化手部建模与实时交互

虚拟人手的实时建模是以人机交互为核心的VR/AR系统中的重要技术难点,传统的基于LeapMotion的手部跟踪视觉反馈仅展示骨架动画信息,缺少应用演示的真实感。由此,提出了一个快速高效的个体化手部建模与实时交互系统,重点阐述了该系统的的工作原理以及算法。以含有骨架信息的静止手模型为模板,使用LeapMotion跟踪用户手的骨架数据作为输入,提出了基于骨骼尺寸的手部模型自动个体化建模算法。提供了一种基于不完整骨骼运动数据的线性蒙皮技术的改进算法,可快速计算不同手部姿势下骨架之间的变换矩阵,动态更新虚拟手的姿势。实验结果表明,此系统在实验的硬件平台上运行速度可以达到60 f/s,误差稳定在4 mm以内,能为人机交互任务实时提供真实可靠的视觉反馈。     

MPEG Audio编码技术初探

如何最大限度地提高数据编码的压缩效率是人们一直追求的目标。在音频编码领域,人类利用自身听觉系统特性来压缩音频数据取得了很大进展,先后制定出MPEG-1Audio,MPEG-2Audio和MPEG-2AAC等一系列音频压缩标准。本文介绍了MPEG编码标准,重点研究了目前应用最为广泛的MP3编解码技术和LAME编码引擎。     

MPEG Audio编码技术初探

如何最大限度地提高数据编码的压缩效率是人们一直追求的目标。在音频编码领域，人类利用自身听觉系统特性来压缩音频数据取得了很大进展，先后制定出MPEG-1Audio，MPEG-2Audio和MPEG-2AAC等一系列音频压缩标准。本文介绍了MPEG编码标准，重点研究了目前应用最为广泛的MP3编解码技术和LAME编码引擎。     

Broadband MPEG-2 Client with Network Configuration Capability

MPEG-2 is a standard for high quality-content compression and data delivery used in digital television and DVD. MPEG-2 is computationally complex but recently it has become possible to perform MPEG-2 decoding in software using multimedia instruction sets of modern microprocessors. This is an important step for the convergence of computers with television and entertainment. In this paper we describe operation and performance of a broadband video client which is MPEG-2 transport stream decoder with network interfaces, implemented on Sun UltraSparc processor using VIS multimedia instruction set. The decoder performs demultiplexing, synchronized video and audio decompression and display in realtime. It is implemented as a Netscape plug-in and it has flexible network interface allowing to configure it for different broadband networks which might be available: ATM PVC, SVC, IP over ATM and Fast Ethernet. Implementation of the decoder in multithreaded and multiprocessing environment is studied. Experimental data regarding the performance of the decoder in different conditions are presented and basing on them conclusions for the processing power requirements are formulated.     

Facial motion cloning with radial basis functions in MPEG-4 FBA

Facial Motion Cloning (FMC) is the technique employed to transfer the motion of a virtual face (namely the source) to a mesh representing another face (the target), generally having a different geometry and connectivity. In this paper, we describe a novel method based on the combination of the Radial Basis Functions (RBF) volume morphing with the encoding capabilities of the widely used MPEG-4 Facial and Body Animation (FBA) international standard. First, we find the morphing function G(P) that precisely fits the shape of the source into the shape of the target face. Then, all the MPEG-4 encoded movements of the source face are transformed using the same function G(P) and mapped to the corresponding vertices of the target mesh. By doing this, we obtain, in a straightforward and simple way, the whole set of the MPEG-4 encoded facial movements for the target face in a short time. This animatable version of the target face is able to perform generic face animation stored in a MPEG-4 FBA data stream.     

Power and performance analysis of multimedia applications running on low-power devices by cache modeling

High processing speed is required to support computation intensive applications. Cache memory is used to improve processing speed by reducing the speed gap between the fast processing core and slow main memory. However, the problem of adopting cache into computing systems is twofold: cache is power hungry (that challenges energy constraints) and cache introduces execution time unpredictability (that challenges supporting real-time multimedia applications). Recently published articles suggest that using cache locking improves predictability. However, increased cache activities due to aggressive cache locking make the system consume more energy and become less efficient. In this paper, we investigate the impact of cache parameters and cache locking on power consumption and performance for real-time multimedia applications running on low-power devices. In this work, we consider Intel Pentium-like single-processor and Xeon-like multicore architectures, both with two-level cache memory hierarchy, using three popular multimedia applications: MPEG-4 (the global video coding standard), H.264/AVC (the network friendly video coding standard), and recently introduced H.265/HEVC (for improved video quality and data compression ratio). Experimental results show that cache locking mechanism added to an optimized cache memory structure is very promising to increase the performance/power ratio of low-power systems running multimedia applications. According to the simulation results, performance can be improved by decreasing cache miss rate down to 36 % and the total power consumption can be saved up to 33 %. It is also observed that H.265/HEVC has significant performance advantage over H.264/AVC (and MPEG-4) for smaller caches.     

A Novel Approach to Lossy Real-Time Image Compression: Hierarchical Data Reorganization on a Low-Cost Massively Parallel System

This paper discusses an innovative real-time oriented image compression system, based on a simple algorithm designed explicitly to be implemented on a low-cost SIMD computer architecture featuring a much lower power consumption than traditional DSPs or dedicated hardware. For this reason the considered approach is suitable to be integrated on portable systems, where power consumption is a critical design issue.The algorithm, based on a hierarchical decomposition of the input image, has been tested on a special purpose SIMD system, PAPRICA, exploiting its features such as its massive parallelism and its capability to operate on local data as well as to handle hierarchical data structures.According to the proposed approach, the quality of the decompressed image can be traded for a lower power consumption as well as a higher processing speed. A comparison between the discussed algorithm and the standard JPEG compression technique is also presented.     

基于并行和预测的方向菱形运动估计算法

对MPEG-4视频编码中的块运动估计算法进行分析,得出算法中存在的并行性。将多核并行计算的思想应用于方向菱形模板的运动估计算法中,并引入一种预测机制来充分提高并行性,得到基于多核并行预测的方向菱形运动估计算法(PPDDME)。在PC机和Omap5910 两个平台上的验证表明,该算法相比串行算法在保证了压缩质量的前提下,有效提高了编码速度。     

基于DirectShow的实时视频信息采集与压缩

论述采用DirectShow技术进行实时视频信息的采集和压缩存储的方法,并给出详细的设计思路。设计中视频捕捉采用WDM驱动捕捉,提高视频捕捉的效率和通用性;采用基于内容的MPEG-4视频编码标准进行压缩,得到较高的压缩比和压缩质量。该技术已经成功地应用到笔者参与开发的视频会议系统中,有效提高了采集速度和视频质量。