Research On Light Field Image Coding Based On Convolutional Neural Network

Light field(LF)imaging technology can capture the light field of a real scene through a micro-lens array structure.It has won the favor of consumers for its simple shooting,continuous viewpoint,and vivid colors.However,in the case of the limited network bandwidth,it has become an urgent problem to effectively encode the light field image captured by the light field camera.Light field images have some characteristics that are different from traditional natural images.Therefore,the novel compression theories and technologies of light field images need to be proposed.Based on this background,this theses focuses on using a convolutional neural network(CNN)to conduct studies from the aspect of luma component variable resolution coding and YCb Cr three-channel variable resolution coding.This theses thoroughly studies the characteristics of light field images and proposes a CNN-based macropixel-level variable resolution coding method for the luma of light field images.Firstly,based on the macropixel distribution characteristics of the light field image,each coding tree unit(CTU)is down-sampled using the proposed micropixel-level down-sampling method.For the reconstructed low-resolution coding unit,this paper proposes a CNN-based macropixel-level upsampling method to achieve the luma upsampling recovery.Finally,by performing rate-distortion optimization(RDO)with the original coding mode,the optimal encoding mode is selected.Experimental results show that the proposed method can significantly save the bit rate while maintaining the same image quality.On the basis of variable resolution coding method for luma,this theses proposes a luma-guided three-channel variable resolution coding method.Firstly,the proposed micropixel-level down-sampling method is extended to YCb Cr three channels.Secondly,based on the channel correlation between the luma component and the chroma component,a luma-guided micropixel-level chroma upsampling method is proposed.Finally,the three-channel variable resolution coding is realized by integrating with the luma variable resolution coding mode.Experimental results show that the proposed method can significantly save the bit rate for three-channel encoding while maintaining the same image quality.