Design of Fast Motion Estimation Algorithms for Video Encoder using New Zero Motion Prejudgment and Initial Search Center Prediction Techniques

Abstract

Agile technical growth in the field of video display and capturing devices has led the researchers and standardisation bodies to develop new standards of video coding. MPEG-X, H.26X and HEVC have been developed in this field for the past three decades. The key component of these video coding systems is the process of motion estimation which takes 80-90% time of a video encoder. Block based motion estimation algorithms are used in these coders for estimating the motion between the current and reference frames. In such algorithms, video frames are divided into fixed/variable size blocks and each block in the current frame is searched for its best match in the reference frame in a given search window. Full search algorithm compares the current block with all the blocks in the search window to find its best matching block. This algorithm provides the optimum results but its computational complexity makes it inevitable for real time applications. This has led to the development of various fixed and adaptive search pattern based algorithms. These algorithms reduce the computational burden but at the same time they compromise with the video quality. So the main aim of any motion estimation algorithm is to reduce the number of computations without deteriorating the video quality. Zero motion prejudgement (ZMP) and initial search centre prediction (ISC) have been proven to be beneficial in accelerating the process of motion estimation. ZMP helps to identify the stationary blocks before the calculation of the actual motion vector and thus saves the computations for calculating the motion vectors of the stationary blocks. On the other hand ISC aims to find an initial location in the search window so that a refined search is carried around this point instead of center of search window. This reduces the number of search steps to attain global minima and thus the number of computations for motion estimation.The main aim of this thesis is to develop fast block based motion estimation algorithms...