The Research Of Fast Coding Algorithm Based On Intra Prediction Mode And Quad-tree Partition In HEVC

High Efficiency Video Coding(HEVC or H.265),the latest international video coding standard,displays a 50%bit rate reduction with nearly equal quality and dramatically higher coding complexity compared with H.264.In this paper,the complexity of intra prediction is studied in further,reducing the complexity of intra coding from two aspects.We first propose an algorithm that combines an early termination method for CU(Coding Unit)partition based on the number of coding bits of the current CU and the reduction of intra prediction modes to decrease computational complexity.The principal results have achieved are as the following:(1)We analyzed the statistical relationship between the best mode and the costs calculated through Rough Mode Decision(RMD)process and proposed an effective mode decision algorithm in intra mode prediction process.We alleviated the computation difficulty by carrying out the RMD process in two stages,reducing 35 modes down to 11 modes in the first RMD process stage,and adding four modes adjacent to the most promising mode selected during the first stage into the second RMD stage.After these two stages,there were two or three modes ready to be used in the rate distortion optimization(RDO)process instead of the three or eight modes in the original HEVC process,which significantly reduced the number of candidate modes in the RDO process and decreased the coding complexity.Experimental results show that the proposed fast algorithm save an average time reduction rate of 36%compared to the test model HM-16.12,with only 1.1%Bjontegaard delta rate increase.(2)We proposed a fast CU partition early termination algorithm that takes advantage of obtaining coding bits earlier to speed up the process of finding the best CU combination.The coding bits of the current coding unit(CU)can marked as the main basis for judging its complexity by analyzing the statistical data.The coding bits of the current CU are used to terminate the CU division prematurely,and the corresponding thresholds are set for different size CUs under different QPs.The number of CU coding bits required under the best intra mode can be obtained,then we judge whether the number of coding bits is smaller than the threshold set by our statistical data.If the number of coding bits is smaller than the threshold,we can end the CU partition early.Otherwise,CU continues to be divided into four sub-CUs.Experimental results show that the two proposed fast algorithms provide an average time reduction rate of 53%together compared to the reference HM-16.12,with only 1.7%Bjontegaard delta rate increase,which is acceptable for Rate-Distortion performance.