H.264运动估计整像素部分算法的改进与实现

【作者】 曹宇辉；

【导师】 王匡；

【作者基本信息】 浙江大学 ， 信息与通信工程， 2006， 硕士

【摘要】 H.264/AVC是目前国际上最新的视频压缩编解码标准。为了实现更高的编码效率,H.264/AVC标准采用了很多新的编码技术,如多参考帧预测、多尺寸编码块模式、1/4像素精度运动矢量、整数变换量化、基于内容的熵编码、新型帧内预测、去除方块效应的滤波器等。 与此同时,H.264/AVC编解码器的计算复杂度与其它视频压缩标准相比,高出了几倍甚至十几倍,需要消耗大量的时间和系统资源。因此,实时编解码器的实现面临巨大的挑战,需要寻找高效的优化算法,以减少巨大的计算复杂度。本文主要从实时视频应用的角度,对H.264/AVC编码过程中运动估计模块整像素部分方面进行了研究。 首先,对H.264/AVC的主要功能模块及其中包含的新技术进行了详细论述。阐述了帧内预测、多种块模式的帧间预测、1/4和1/8像素的运动估计、多参考帧、整数变换、CABAC和环路解块滤波器等新技术,等等。 其次,详细介绍了运动估计已有的各种算法,提出了一种改进的适合软件的快速算法——双六边形与小菱形结合的搜索算法。运动估计是基于运动补偿/DCT混合编码方法的重要组成部分,运动估计与补偿技术可以有效地去除视频序列相邻帧间存在的时间冗余,极大地提高了编码效率。 第三,根据H.264/AVC的特点,提出了一种基于VLSI的快速搜索算法——扩展三步搜索算法,该算法在搜索窗内搜索点数和搜索步数固定,搜索点排列整齐而有规律,算法复杂度低,易于硬件实现,然后作了分析和软件测试,给出了算法的硬件结构。 最后,提出对H.264/AVC标准帧内预测部分的改进建议,并做了软件测试和结果分析。更多还原

【Abstract】 H.264/AVC is the newest international video coding standard. For the enhancement of the coding efficiencies, the new standard adopts new tools as followed: multiple reference picture, variable block-size with seven block sizes in motion prediction, quarter-pixel accuracy for motion vector, short word-length integer transform, context-adaptive entropy coding and loop filter deblocking.At the same time, the complexity of the H.264/AVC codec is several times higher than that of existing standards (MPEG-2 and H.263). Accordingly, the real-time video codec demands higher-powered processor and faster-speed algorithms. So the main endeavor of this paper is to achieve maximal processing speed and better video compression quality through optimization for integer pixel motion estimation in the H.264/AVC encoding process.Firstly, the main function modules of H.264/AVC is elaborated and its new techniques being adopted. It is expounded that the application of intra prediction, multi-block inter prediction, 1/4 and 1/8 fractional pixel motion estimation, multiple reference frames, integer transform, CABAC and deblock filter, etc.Secondly, Some search algorithms departed are elaborated, and a double hexagon and diamond search algorithm is proposed. Motion estimation is one of the most important part of motion compensation/DCT based hybrid video coding standards which lead to high compression ratio by efficiently reducing temporal redundancy between adjacent frames of video sequence.Thirdly, according to the characteristics of H.264/AVC, a motion estimation fastalgorithm based on hardware------Extended Three-Step Search algorithm is proposed.the VLSI implementation complexity of motion estimation in video encoding is analyzed. Furthermore, VLSI architecture of the algorithm based on hardware is presented.Finally, a recommendation is proposed that improve on the part of intra prediction in H.264/AVC Recommendation, and tested in JM by modifying the corresponding part whose result shows that performance in using our algorithm achieves much higher coding efficiency compared to current standards.更多还原