Research On Fast Decision Algorithm Of Intra Prediction CU For VVC

With the widespread adoption of ultra-high-definition video,the previous standards are no longer sufficient to meet the compression capabilities required for video storage and transmission.For this purpose,a new generation of video coding standard VVC(Versatile Video Coding)emerged as the times require.During the development of the encoder,the coding performance has been continuously improved and the complexity of the encoder has also been greatly increased.Therefore,how to reduce the complexity of the coding process has become the main research contents.In this thesis,two fast algorithms are proposed for the decision of coding unit in intra-frame prediction module,including fast split of coding unit and fast decision of Intra Sub-Partiton mode.The main research contents and work results of this thesis are as follows:(1)In order to reduce the complexity of the coding unit split process,a fast decision algorithm based on the similarity of adjacent sub-regions for multi-type tree is proposed.The algorithm uses the similarity of the residual information of adjacent sub-regions to predict the possible split methods of the luminance coding block with a size of 32×32,avoids unnecessary multi-type tree division method searches during the ratedistortion optimization process,and speeds up the coding process.The algorithm adopts a merging strategy for the adjacent sub-regions with the highest similarity to determine the most likely multi-tree split methods.Compared with the VVC reference platform VTM-6.1,under All-Intra encoder configuration,the algorithm obtains about 50.91%encoding time saving,while BDBR is 1.50%and BD-PSNR is-0.07db.(2)To reduce the complexity in the decision process of intra prediction of coding unit,a fast intra decision algorithm based on the directions of gradient is proposed.The algorithm first calculates the gradient values of the residual information in the directions of 0°,45°,90°,and 135°,and measures the texture complexity of the CU with the value of the maximum gradient.Skipping the calculation of ISP mode for the texture flat CU achieves the purpose of shortening the encoding time.Compared with the VVC reference platform VTM-6.1,under All-Intra encoder configuration,the algorithm obtains about 12.64%encoding time saving,while BDBR is 0.41%and BD-PSNR is-0.02db.Both algorithms effectively save coding time on the premise of ensuring a small loss of coding performance and a loss of video image quality that is undetectable to the human eye.