论文标题:H.264软件编解码器的性能研究与优化
Exploration of GMPLS System Implementation
论文作者 熊赟
论文导师 于鸿洋,论文学位 硕士,论文专业 信号与信息处理
论文单位 电子科技大学,点击次数 478,论文页数 72页File Size2223k
2005-05-01论文网 http://www.lw23.com/lunwen_344957/ 视频压;、H.264;运动估计;SIMD
Video Compression; H.264; Motion Estimation;SIMD
二十世纪九十年代以来,JPEG、H.263、MPEG-1、MPEG-2 等图像多媒体国际标准相继出台,它们成功地应用于多种实用场合。但是,随着时代的发展、Internet 的普及,以及对视频传输需求不断提高,现有的这些视频压缩标准明显存在着一些缺陷和局限性。为了克服这些缺点,结合目前软硬件发展的情况,ITU-T 在继H.261,H.263 等视频压缩标准之后,制定了新一代视频压缩标准,并正式命名为H.264。新一代标准H.264 可以得到更好的压缩图像效果、拥有更多的功能和更大的灵活性。本文首先介绍了多媒体技术发展的状况以及视频压缩的基本概念和方法,然后分析了H.264 编解码器的基本结构和实现流程,以及H.264 协议所采用的一些先进技术,如基于多种运动矢量模块的运动估计、帧内预测,整数变换和去块效应滤波等。正因为H.264 具有这些新特点,它才可以得到优良的性能, 今后也将得到更加广泛的应用。H.264 虽然具有很多优良性能,但是它的运算量也是十分巨大的,其编解码速度也都比较慢,在通常的条件下,无法满足实际应用的要求。本文在细致的分析了其编解码器后,对于解码器,编码器都采用了多种方式进行优化。对于解码器:首先调整了解码程序的流程,减少了对内存的访问;然后对于整数变换和非整数像素点的插值运算采用了MMX 和SSE 指令进行优化;对于一些使用较频繁的简单函数改用嵌入内联汇编函数的形式,使得解码器性能大为提高。为了便于使用,还把解码器封装成库文件,并用于WINDOWS环境下的播放器中。对于编码器中和解码器相似的部分采用了同样的方法优化。在它的运动估计部分,对于SAD 值的计算采用MMX 指令进行并行计算。最后把优化前后的编解码器性能进行比较。结果表明,优化后的编解码器在保证其优良性能的前提下,达到了缩短运行时间的目的。
Entering 21 Century,the adoption of digital video has been fuelled by the development of many video coding standards in many applications, which are targeted in different application areas. There are many video protocols such as H.26x and MPEG-x. However the requirements for video transmission are increasing with the prevalence of Internet, so the video protocols are not applicable nowadays. Therefore ITU-T put forward and released a new protocol for video compression —H.264. It has many different features and its efficiency is improved through added flexibility and functionality. Firstly, the dissertation introduced the history of the multimedia technology, the basic concept and method of video compression. Then, it described the main structure and the flow of H.264 encoder/decoder. It used a lot of advanced technologies, such as the motion estimation based on multiple-modes motion vectors, intra-prediction, integral transform, loop filter. So it can achieve excellent performance, and will be used widely in future. In despite of its excellent performance, the quantity of calculation is excessive. So the decoder/encoder of H.264 runs very slowly. In general, it is hard to meet the requirement of real time applications. In this dissertation, we analysed the decoder/encoder of H.264 carefully, then adopted various ways to optimize it. In decoder: firstly, we adjusted the flow of the decode program, reduced the times of memory access; secondly, we use the MMX and SSE instruction to optimize the integral transform and sub-pixel interpolation,adjusted some simple but high frequency called functions to inlined asm function. For convenience to use, we made the decoder program to a library, and use it to make a player in windows environment. In encoder: the main methods to optimize are similar with decoder. In the part of motion estimation, we used the MMX instruction in the parallel calculation of the SAD. In the end, the dissertation compared the performance of the optimized decoder/encoder with the original. The result indicate the optimized decoder/encoder have cut down the running time while maintaining the performance.
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