HEVC Intra-frame Fast Mode Selection Algorithm For Ultra High Definition Video

The 21 st century is the information age,a variety of media develop rapidly,including video transmission.The development of video is gradually moving in the following directions: High definition,High frame rates and High compression rate.Faced with the above development trend,the HEVC standard has proposed.HEVC focuses on high-definition and ultra-high resolution video.While guaranteeing the same video image quality,the code rate of the video stream is reduced by 50%,which can better adapt to different network environments and support new technologies such as multi-core parallel codec.However,HEVC has also brought high computational complexity to high performance coding,which is obviously unfavorable to the commercialization of HEVC.Therefore,how to reduce the algorithm complexity and reduce the coding time is very important while keeping the HEVC coding efficiency.Intra prediction is one of the most important parts of HEVC.It is a complicated module in HEVC coding framework,which is difficult to meet the needs of practical applications.Therefore,it is necessary to optimize the intra prediction algorithm.Aiming at the problem of excessive coding time caused by the high computational complexity of intra prediction,this paper mainly studies a HEVC fast intra mode decision algorithm which is supported by using the correlation of neighboring coding units and gradient analysis.The main work and results of this paper are as follows:(1)An adaptive depth and decision cutting algorithm is proposed.First,according to the depth of nearby coding unit,to do depth prediction of the coding unit and obtain its prediction depth.Then according to the space information of CU,the relationship among parent CU,RMD list and MPM,cut out the unnecessary prediction patterns.This algorithm is expected to reduce the computational complexity of the original standard algorithm without affecting video coding efficiency.(2)An intra prediction mode decision algorithm based on gradient is proposed.In the base of depth adaptive decision algorithm and intra prediction mode candidate list clipping algorithm,intra prediction mode decision algorithm based on gradient is proposed.In this algorithm,the candidate mode is computed by gradient if the candidate mode number is lager than 2.After that we can determine the best prediction mode finally.Combing this algorithm with the algorithm proposed in Chapter 3,we can save 29.16% coding time on average in case of adding 1.34% BD-rate and reduce 0.09 dB BD-PSNR.(3)Based on the detailed description of the algorithm principle of two key technologies,we compare the advantages and disadvantages of these methods with the experimental analysis.Combing the algorithm proposed in Chapter 3 with the algorithm proposed in Chapter 4,we can save 29.16% coding time on average in case of adding 1.34% BD-rate and reduce 0.09 dB BD-PSNR.