导　　师： 侯正信;李桂苓

学科专业： H1002

授予学位： 硕士

作　　者： ;

机构地区： 天津大学

摘　　要： 随着数字音、视频及多媒体技术的发展，视频编码技术得到快速发展。应用于不同领域的mpeg-1、mpeg-2、mpeg-4、h.26x等国际编码标准以及我国自主开发的avs视频压缩编码标准相继出台。为了适应用户终端的多样性以及网络自身的传输特性，需要将已压缩的视频码流进行转换，即转换编码，以实现网络间的资源共享。 将经过压缩的视频数据进行远程传输时，需要考虑网络拥塞、信道带宽及终端处理能力。码率控制策略的目的就是通过调整编码端的编码参数，保证信道正常传输，并获得尽可能好的图像质量。 作为对视频转换编码及码率控制研究的基础，本文首先对转换编码结构以及mpeg-2和avs视频编码标准建议的码率控制策略进行了介绍。接着，对影响输出码率的因素和码率控制中关键问题进行了分析，为提出新的码率控制算法打下基础。 论文在分析两个编码标准特点和解码信息基础上，提出了适用于mpeg-2到avs转换编码的码率控制算法。包括：帧层比特分配策略优化，即根据解码信息，给不同复杂度的帧分配不同编码比特数；宏块层目标编码比特数实现算法，即利用ρ域线性源模型建立量化与比特率准确关系。最后，结合avs编码标准建议的码率控制策略及本文提出的改进算法，实现了输出码率的有效控制。 课题组开发了将mpeg-2标准的dvd码流转换为avs标准ts流的视频转换编码系统。本文第二部分总结了已完成的基于directshow的avs ts流播放器软件开发工作，包括一路avs节目音视频流的分割模块和avs视频流解码模块的设计和实现。 Along with booming digital AV and multimedia technology, video coding technology has greatly developed. Nowadays, the International Coding Standards, such as MPEG-1, MPEG-2, MPEG-4, H.26x and Chinese independently creating AVS have been established and applied to different areas. In order to adapt to heterogeneous client terminals and transmission characteristic of networks, pre-encoded video should be transcoded into another coding format. So, the resources of networks can be shared. When the compressed video sequence experiences long-distance transmission, network congestion, channel bandwidth and disposal ability of terminal should be considered. Target of rate control is to maintain the channel normal and obtain better image quality by adjusting the parameters of encoder. As the basis of the following research on rate control of transcoding, several transcoding structures and the recommended rate control methods of MPEG-2 and AVS coding standards are introduced in the thesis first. And then, the affecting factors of the bit rate and key part of rate control in transcoder are analyzed, which are theories basis of the new algorithms. On the basis of full analysis on the characteristics of two coding standards and information adopted from decoder, this thesis proposes two algorithms. One is bit allocation optimization in frame layer, namely, different bits are allocated to frames with different complexity according to decoding information. The other is the establishment of accurate relationship of quantitative parameters and bits inρ-domain. Finally, by combined rate control strategy in AVS, the new rate control scheme implements effectively control. Our lab group has developed a system which can transcode DVD stream to AVS TS stream. The second part of this thesis summarizes the software developing for AVS TS player using DirectShow framework, which consists of an AVS audio//video splitter filter and an AVS video decompressor filter.

关 键 词： 视频转换编码 码率控制 标准 编码标准

分 类 号： [TN919.81]

领　　域： [电子电信] [电子电信]