Research On Fast Intra Coding Algorithms Based On Texture Characteristics For Virtual Reality Video

One of the hallmarks of virtual reality video is its immersive experience,which allows users to have intuitive real-time perceptions and feel an immersive experience.The Joint Video Exploration Team(JVET)incorporates VR video coding into the next standard range and proposes a virtual reality 360 degree video solution.The resolution of a VR video is ultra-high(generally 4K to 8K),that causes difficulties for the encoding of such videos,especially for real-time transmission.The paper focuses on the intra-frame coding problem of virtual reality video,and proposes a fast intra-frame coding algorithm based on texture characteristics.The algorithm is divided into two aspects.On the one hand,a fast CU partitioning algorithm based on texture complexity is proposed.For the image texture features of ERP format,in the two poles of the video image,it have the higher stretch and sampling rate.The CU texture of these parts is simple and suitable for larger CU block to encoded,and the video information contained in the middle portion of the video image is too large,and needs to be encoded with a relatively small CU.Based on this discovery,in the process of intra prediction CU partitioning,the algorithm determines whether to further terminate the further division of the coded CU according to the image texture complexity,and reduces the calculation amount of the RD-cost in the CU partition process by determining the depth of the CU block in advance.Experimental result shows that the BD-rate loss of this algorithm is 0.2%,and the average coding time is about 33%.On the other hand,a fast algorithm based on texture direction selection mode is proposed.In the intra prediction coding mode selection process,the algorithm reduces the number of candidate modes in the mode selection process according to the judgment of the image texture direction.The BD-rate loss of this algorithm is 1.2%,and the average coding time is about 34%.Both two algorithms encode and optimize the VR video coding through image texture characteristics,which together constitute the fast algorithm of intra-frame coding based on texture characteristics proposed in this paper.The experimental results show that this fast intra-frame coding algorithm based on texture characteristics can reduce the coding time by about 53%on average,while the BD-rate only increases by 1.3%,which is almost negligible.