Comprehensive scheme for subpixel variable block-size motion estimation

摘要

Fast variable block-size motion estimation is a key issue fornreal-time applications of the H.264, whereas the subpixel refinementntakes up much computational time as compared to integer-pixel mo-ntion estimation. We propose a new fast subpixel precision variablenblock-size motion-estimation scheme. This algorithm uses the sta-ntistical information, which comes from the motion activities of thenmacroblocks (MBs) in the previous frame, to predict the character-nistics of MBs in the current frame. Additionally, the distortion valuesnand motion vectors of MBs in the previous frame are also considerednas prior knowledge, based on which we can make decisions on earlynmode selection and early termination, and on whether or not to skipnsome candidate modes and candidate checking points. The interme-ndiate results of subpixel motion estimation are used together with thenprior knowledge to reduce subpixel search time when searching fornstationary blocks. Our new directional information strategy is usednin both integer-pixel motion estimation and subpixel motion estima-ntion to accelerate the search procedure. Moreover, our algorithm canneliminate the subpixel motion estimation of all the unselected sub-npartition modes. The computational resources can then be spent onnthe modes and locations that deserve to be searched more than oth-ners. Extensive experimental is been done, the results of which shownthat the speed of our approach is nearly five times that of the fastnalgorithms in H.264 JM, with a better peak signal-to-noise ratio andnbetter bit performance