改进的h.264码率控制算法分析-analysis of improved h 264 code rate control algorithm.docx

摘要H.264/AVC 标准是国际电信联盟 ITU 和国际标准化组织 ISO 联合提出的最 新一代视频压缩编码国际标准，该标准以编码结构复杂和计算复杂度增加的代 价，换取了比其他标准更高的编码效率，在相同的重建图像质量下，H.264 比 H.263 节约了 50％左右的码率。由于其有更高的压缩比和更好的 IP 和无线网络 信道的适应性，在数字视频通信和存储领域得到了越来越广泛的应用。码率控制技术是影响视频编码器编码效率的关键因素之一，其主要任务就是有效地控制视频编码器，使其输出码流的大小满足传输信道实际带宽的限制，并 且，尽可能获得最优的解码图像。因此，研究和开发面向 H.264/AVC 的码率控 制算法对于 H.264 视频编码标准能否得到广泛普及以及进一步研究和发展视频 压缩和通信技术具有十分重要的理论意义和应用价值。本文介绍了视频压缩编码基本原理以及视频编码的发展历程，并描述了 H.264 视频编码标准的编解码器结构和关键技术。在分析和比较三种经典的码率 控制算法的基础上，详细介绍了 H.264 码率控制算法的三层结构，即图像组（GOP）层、帧层、基本单元层，本文基于帧层和基本单元层的码率平均分配原 则，从编码帧的复杂度和其内部宏块复杂度的两个方面进行考虑，提出了一种改 进的帧层和宏块级的码率控制算法，并对算法在 H.264 参考软件 JM95 上进行了 仿真实验。结果表明，与 JM95 中采用的码率控制算法相比，改进后的算法获得更好PSNR 值和更精确的实际编码比特率。关键词：码率控制；码率分配；帧复杂度；基本单元层；宏块；AbstractH.264/AVC is the newest video coding standard of the ITU-T Video Coding Experts Group and the ISO/IEC Moving Picture Experts Group, which has far higher coding efficiency than the former standards at the expenses of complex codec structure and calculation. H.264 can save 50% bitrates than H.263 with the same constructed picture quality. Therefore, it is provided with excellent coding performance and network adaptability, it is popular in the digital video communication and memory domain.The rate control technology is one of the key point of the codec efficiency, which can control the video codec efficiently, make the output bitrates meet the fact bandwidth of the channel. Thereby, developing and studying rate control for H.264 is provided with important theory and application value for promotion of H.264 as well as further study and development of video compression and communication technique.Firstly, the principle of video coding technique and the development history of video coding standard is introduced in this paper. Then, the structure of H.264 video encoder and its some key techniques is described. The classical rate controlalgorithms is analyzed totally, the three structure of H.264 rate control is emphasized，that is GOP layer, frame layer, basic unit layer. Considering the