【作者】 罗鸣；

【导师】 龙建忠；

【作者基本信息】 四川大学 ， 模式识别与智能系统， 2004， 硕士

【摘要】 本文主要讨论了目前最新的视频编码标准H.264。H.264作为新一代的视频编解码标准，采用了成熟的技术，在追求更高的编码效率和简洁的表达形式的同时也提供了非常好的视频质量，是当前最高效的视频压缩方法。相对于其他视频编解码标准，H.264具有更广阔的应用前景。 H.264采用了分层结构：视频编码层(VCL：Video Coding layer)负责高效的视频内容表示；规定网络传输规范的网络抽象层(NAL：Network Abstraction Layer)负责以网络所要求的恰当的方式对数据进行打包和传送。帧内预测编码、多参考帧的运动估计技术、可变尺寸块的运动估计、整数DCT变换、环路滤波器、CABAC等先进技术是H.264良好压缩性能的基础，本文分别对这些技术的算法进行了详细分析。同时，本文还分析了利用率失真优化选择算法在各种编码、预测模式中进行选择的基本原理和实施。 通过对H.264编码器的深入分析和研究，本文提出了对编码器的运算速度进行优化的方案并加以实施。优化的关键在于确定优化对象，本文对确定优化对象的方法和思路进行了介绍。优化过程的第一步是利用MMX／SSE2技术对核心运算模块进行并行运算，并调整数据在内存中的排列以加速对数据的读取；然后通过调整程序结构，减少了许多不必要的函数调用，消除了这类函数对程序运行速度的影响；最后，本文还提出了一种新的考虑梯度的十字优先钻石运动搜索算法，在不影响编码质量的前提下，极大的提高了运动搜索得效率。经过优化后的代码较优化前速度有了2.5—3倍的提升。更多还原

【Abstract】 Abstract In this paper, a discussion of the emerging video coding standard, H.264. is carried out. As a new video codec standard, H.264 applies many mostly used technologies, it provides fairly good coding quality while achieving a better coding efficiency and more simple syntax expression, and it is the most efficient video coding standard at present. Comparing to prior video codec standards. H.264 seems will he used in more application areas in the future.The H.264/AVC design covers a Video Coding Layer (VCL), which efficiently represents the video content, and a Network Abstraction Layer (NAL). which formats the VCL representation of the video and provides header information in a manner appropriate for conveyance by particular transport layers or storage media. Three are many new technical used to H.264 codec: Intra prediction, multi-picture motion-compensated prediction, Variable block-sized motion compensation with small block size, Quarter-sample-accurate motion compensation. Integer DCT transform, Loop-filter, CABAC for entropy encoding, etc, all these new technical and their algorithms will be discussed in this paper. The so called rate-distortion optimization selection method being applied in H.264 for selecting the best mode between many choices is also discussed in this paper.The way to speed up the video encoder is also introduced in this paper. The key to perform encoder optimization is to make sure which part of the encoder is themost lime-consumption part. The way to locate the time-consumption part is discussed first. After that, three ways to perform The optimization is introduced : first of all. the way to use MMX/SSE2 technology lo speed up the core computing part is introduced; secondly, discussion on how to reduce the unnecessary calls of some I’unclions is taking place; at last, a novel fast motion estimation algorithm based on NCDS algorithm is proposed, which is provided not only more efficient than many famous fast motion estimation algorithm, but also maintains good performance comparing to the basic FS algorithm. Fxperimcntal result shows that after being optimized, the new encoder achieves a 2.5-3 speed up over the original one.更多还原