The Research And Improvement Of Motion Estimation Algorithm Based On H.264 Standards

H.264 is the newest video coding standard of the Joint Video Team (JVT), formed by the ITU-T Video Coding Experts Group (VCEG) and the ISO/IEC Moving Picture Experts Group (MPEG). Some new technologies are provided to enhance the coding efficiency, including variable block-size motion compensation, multiple reference picture motion compensation, integer transform, context-adaptive binary arithmetic coding, in-loop deblocking filter etc. The features of the new design provide approximately 50% bit rate savings for equivalent perceptual quality relative to the performance of prior standards, such as H.263 and MPEG-4. But the improvement of coding efficiency is at the cost of the high calculation complexity. The Coding complexity of the H.264 encoder is more than ten times than that of the H.263 or MPEG-4. According to the characteristics of H.264, universal algorithm optimization methods consist of fast motion estimation, multi-reference picture selection, fast intra prediction mode selection, optimization of CABAC and in-loop deblocking filter etc。Because the motion estimation and motion compensation is the most important bottleneck for the Computational complexity and coding time.In order to Improve operational efficiency, several fast algorithms have been proposed recently to reduce encoding time and Computation.Full search which is based on the block-matching method is the most basic search algorithm, it searches each point covering the full search window, and too much computation leads to very slow search speed which places great impact on its application. In order to reduce the complexity of H.264 encoder, people developed a lot of fast search algorithms, such as three-step search method (TSS), two-dimensional logarithm (TDL), the cross-search (CS), nearest neighbor search method (NNS), conjugate direction search (CDS), and block-based gradient descent search method (BBGDS).In this paper, we have presented some new coding technology of H.264, and then analyzed its reference model JM 12.2 version, and deeply researched several motion estimation algorithms in JM, for example, full search, Unsymmetrical-cross Multi-Hexagon-grid Search, Simplified Unsymmetrical-cross Multi-Hexagon-grid Search and Enhanced Predictive Zonal Search algorithm. And several fast search algorithms used commonly are compared and improved. The early termination method of partial residual computation is added, and the candidate block which has been searched previously is marked. The points of searching template are selected to search in optimal order. Therefore, the improved algorithm method maintains smaller SNR loss and further increases search speed. In addition, we have proposed improved EPZS algorithm, In order to judge the characteristics of block's motion, we make use of the characteristics of predictive vectors in time and spatial domain and the relationship between them. Particularly, for the blocks which have small motion, we set rapid Jump search to avoid unnecessary predictive vector sets and wipe out a lot of redundant search time.