【作者】 肖敏雷；

【导师】 满家巨；

【作者基本信息】 湖南师范大学 ， 计算机软件与理论， 2008， 硕士

【摘要】 H.264是由ITU-T VCEG和ISO/IEC MPEG联合推出的新一代国际视频编码标准,它采用的依然是基于块的运动补偿和变换的混合编码方案,但和其它视频编码标准相比,它采用了一种全新的近似DCT变换技术——整数变换技术以避免以前标准中使用DCT变换所带来的反变换匹配误差,采用帧内预测编码以提高帧内及帧间编码效率,帧间采用灵活多变的不同块大小来准确描述物体的实际运动情况,且使用了高精度的分数像素运动估计与补偿以及多参考帧选择技术来增加预测的准确度,采用自适应滤波器以去除图像的边界效应,采用基于上下文的二进制编码技术以缩减编码所需的位数等等,这些新技术的综合运用使得H.264编码器和以前的视频编码标准相比在同等重建图像质量下能够节约大约50%的码率,但H.264编码器所使用的新技术也直接导致了其实现的高复杂性,作者通过对各种视频编码标准的仿真比较发现,H.264虽然获得比其它标准更高的编解码质量,但编解码速度比其它视频标准慢,从而限制了其在实时领域里的应用,因此,如何以较低的实现复杂度获得较高的编码效率就成了H.264视频编码技术走向实时应用的一个重要研究课题。为了达到实时的编码效果,必须寻找相应的快速实现算法来替代H.264中那些复杂度极高的算法;同时为了进一步提高H.264的编码速度,除了对算法进行优化以外,可以对编码器中反复使用的一些功能模块根据平台的特点进行指令级的优化,此外,还可以根据实际需要对整个H.264编码器的程序结构和数据结构进行适当的优化,本文依据这一思路对H.264编码器中所使用的部分关键算法进行了比较。把上述有关算法综合运用到H.264编码器中,在参考软件JM8.6框架下对程序与数据结构进行了适当优化,并对一些关键模块如整像素运动估计中求残差的绝对误差和SAD,分数像素运动估计中求残差的Hadamard变换及对变换后的残差矩阵求取绝对值和SATD,整数变换及其逆变换,亚像素内插等模块利用PC机的多媒体指令系统进行指令级优化,取得了比较满意的加速效果。更多还原

【Abstract】 H.264 is the newest international video coding standard proposed by the Joint Video Team of ITU-T VCEG and ISO/IEC MPEG. H.264 also uses hybrid video coding scheme based on motion compensation and transform. In order to avoid the matching error in IDCT caused by DCT in prior video standards, H.264 utilizes a new approximate DCT transform—integer transform. H.264 uses intra prediction to promote the intra encoding efficiency. It adopts variable block sizes, high exact fractional motion estimation and compensation and multi-reference frame selection to describe exactly the actual motion vector of objects. In order to eliminate the marginal effect, H.264 uses adaptive in-loop deblocking filter. H. 264 uses CABAC to decrease the bits needed for encoding and so on. H. 264 can decrease about 50% percent of bit rates with the same reconstructed picture quality comparing with prior standards by using above advance in video coding technology. But the high efficiency leads to high complexity of implementation directly. The various video coding standard Simulation comparison show that H.264 obtain a higher quality than any other video coding standard, but encode speed slower than other video standard, this will limit the application of H.264 in real time video coding. So it is important to implement the H.264 coder with low hardware complexity and high encoding efficiency.In order to achieve high encoding efficiency, H.264 uses a great deal of encoding algorithms with high complexity. These complexity algorithms will limit the application of H.264 in real time video coding. So we must find corresponding fast algorithms to replace those with high complexity in H.264 reference software. In the mean time, in order to accelerate H.264 encoder, those modules used repeatedly in H.264 should be optimized in multimedia instruction. Moreover the structure of program and data for H.264 encoder can be modified according to the actual needs. According to above ideas, this dissertation gives deep research on some key algorithms and the implementation of H.264 encoder under the reference software JM8.6 in PC with high speed and efficiency. The main creative works are as follows.The above mentioned algorithms were embedded in the H.264 reference software JM8.6 and the structure of program and data are also optimized properly according to actual needs. Some key modules such as computing the sum of absolute difference SAD in integer pixel motion estimation, computing the Hadamard transform of difference matrix and computing the sum of absolute difference SATD, integer transform and its inverse transform, sub-pel interpolation were optimized with multimedia instructions of PC, it achieved satisfied effects.更多还原