【作者】 刘娟；

【导师】 刘文予；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2007， 硕士

【摘要】 随着数字信息技术的迅猛发展,人们对多媒体通信业务的需求与日俱增。应用在无线移动环境下的多媒体业务也成为第三代以及第四代移动通信发展的核心。视频编码作为多媒体技术的关键,对于多媒体通信的发展和推广起着至关重要的作用。本文在国家自然科学基金项目——“无线信道下的信道广义率失真模型研究”(No.:60372067)、华为高校合作项目——“AVS视频标准提案技术研究”以及武汉市青年科技晨光计划项目——“无线多媒体通信的联合功率率失真模型研究”(No.:20045006071-18)的联合资助下,对基于内容的帧间预测技术进行深入研究,同时参与AVS(Audio Video Coding Standard Work group of China)工作组,进行视频编码技术的研究和标准制定工作。近几年,针对在无线移动视频传输应用中所面临的较大处理能力需求与有限能量供给之间的矛盾,如何达到编码效率和复杂度两者之间的平衡成为了视频编码领域中新的研究热点。帧间预测是视频编码中的关键技术,对编码效率和复杂度起着决定性的作用,将帧间预测作为切入点是解决上述问题的良好途径。本文在对典型视频序列做了大量的实验统计和理论分析的基础上,分析了帧间预测技术中可利用的相关性和视频内容特点,对运动矢量的预测和子像素的搜索策略进行了改进,提高了编码效率,并有效降低了视频编码的复杂度。在运动矢量预测部分,本文针对传统预测方法中只利用空域信息的特点,提出了一种自适应的时空域联合预测方法,通过判断相邻块运动矢量的相似程度来确定预测的运动矢量从空域相邻块或时域对应块中获得。实验结果表明,与传统空域方法相比,在基本不增加复杂度的情况下,预测的运动矢量更加准确,编码效率更高。在子像素的搜索部分,本文通过分析最佳搜索点位置的概率分布特性,利用前一帧和已搜索得到的子像素位置的信息,来选择需要搜索的子像素点。实验证明,本文的算法与传统的全搜索方法相比,在保持编码效率的同时,平均搜索点数减少了70%以上,编码器的复杂度显著降低。另外,针对IPTV和视频监控等业务的广阔应用前景,本文介绍了基于独立平台的AVS-P2解码器(AVS-P2 Golden C Decoder),以宏块为单位完成解码过程。相对于帧级解码器,AVS-P2 Golden C解码器有效地降低了时间和空间复杂度,有利于宏块级的并行操作,为实现面向特定应用平台(例如DSP)的嵌入式解码器打下了基础。本文通过利用视频序列图像的相关性和内容特点,对帧间预测算法进行了改进,达到了编码效率和复杂度之间良好的折中。对于解决移动视频应用中的瓶颈,为其在下一代移动通信中的广泛应用提供了有效的实用解决方案。基于独立平台的AVS-P2解码器在AVS的产业化道路上也有着广泛的应用价值。更多还原

【Abstract】 With the rapid development of information technology, the demand for multimedia communication is growing day by day. Especially the multimedia applied in wireless mobile condition is becoming the key componet of the third and fourth generation mobile communication system. As the inevitable part of the multimedia technology, video coding plays a vital role in the development of the multimedia communication. Co-sponsored by the National Science Fund of China——“Research on General Rate-Distortion Model on Wireless Channel”(Grant No.: 60372067), cooperated project with HuaWei company——“Research of Proposals for AVS Video Coding Standard”and Youth Chenguang Program of Wuhan——“Research on Joint Power-Rate-Distortion Model for Wireless Mutimedia Communication”(Grant No.: 20045006071-18), this thesis coducts an in-depth research on the inter prediction technology based on content. Meanwhile, we have participated in the AVS (Audio Video Coding Standard Work group of China) workgroup including proposing the technical proposals and the standard establishment.In recent years, toward the contradiction between the calculation capability requirement and limited energy supply, how to balance the coding efficiency and complexity becomes a hot issue in video coding field. As the key technology in video coding, inter prediction acts a decisive role for coding efficiency and complexity. Inter prediction is deduced to be an ideal cut-in point to this solution. Based on the experiment and theory analysis on typical video sequences, the useful correlation and content characteristics in inter prediction is analyzed to improve the motion vector prediction part and search scheme for sub-pixel search. In the motion vector prediction part, different from the traditional spatial prediction, an adaptive spatio-temporal prediction scheme is proposed. In the proposed scheme, the predicted motion vector is choosed from spatial neighbouring or temporal correlated block by the correlation degree of the neighbouring motion vectors. Experiment results show that with little complexity increasement, the predicted motion vectors are more accurate compared to the traditional method. In the sub-pixel search part, by analysis of the probability distributing of best search position, the sub-pixel points are selected utilizing the sub-pixel information in the previous and current frames. Experiment results show that the search points reduced more than 70% compared to the full search while keep the coding efficiency.In addition, macroblock based AVS-P2 Golden C decoder is introduced for the bright foreground of IPTV and video surveillance application. Compared to the frame based decoder, the Golden C decoder can reduce both temporal and spatial complexity effectively, also in favor of the parallel operation of macroblocks. The Golden C decoder lays foundation for the embedded codec on special flat (e.g. DSP).Taking advantage of the correlation and content characteristic in video sequences, the improved inter prediction algorithm achieved acceptable tradeoff between coding efficiency and complexity. It provides an effective solution to the bottleneck of mobile video application in the next generation and holds extensive application value in the AVS industrialization process.更多还原