The Research Of Motion Estimation Algorithms In H.264

H.264 is the latest video coding standard, jointly developed by ITU-T VCEG (Video Coding Experts Group) and ISO / IEC MPEG (Moving Picture Experts Group). It can achieve higher coding efficiency than MPEG-4, especially in low bit-rate , and is more suitable for low-bandwidth, high-quality network video applications.But while improving the quality and reducing the bit-rate, H.264 increased the codec complexity of computation dramatically. After extensive analysis of H.264, motion estimation is one of the core technology, but also the most time-consuming part. For example , in a single-reference frame and multi-reference frame prediction, the computation of motion estimation respectively account for about 60%, 80% of the total computation . Therefore, how to improve the efficiency of motion estimation, and make the search process more robust, faster and more efficient has become a focus of current research.This thesis introduces the protocol and principle of H.264 and the algorithm of motion estimation in detail firstly, then optimizes the algorithms of the motion estimation from the follow three aspects to accelerate the process of motion estimation. (1) Adaptive Dynamic Search Range Algorithm, determining adaptively the unsymmetrical search range in negative/positive direction of horizontal/vertical axis according to the Predictive Motion Vectors set to reduce the search points. (2) Fixed-mode Fast Motion Estimation Algorithm, mainly focus on the improvements of the existing UMHexagonS algorithm, to further enhance the computational performance of Motion Estimation. (3) Fast Mode Selection Algorithm of Macroblock, utilizing the probability distribution of the various modes and Spatio-Temporal correlation of macroblocks to reduce the number of modes required to compute. Extensive experiments show that these algorithms can achieve significant computational reduction of motion estimation, compared with the previous algorithms in Joint Model (JM) , while maintaining almost the same quality of reconstructed pictures.