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Unequal Error Protection for 360 VR Video Based on Expanding Window Fountain Codes

360 virtual reality (VR) video is one of the popular VR applications. Because VR video transmission needs giant bandwidth resources to guarantee users' quality of experience, plenty of schemes have been proposed to optimize the transmission of VR video. Most of these schemes aimed to reduce the data size of VR video source, thereby reducing the bandwidth requirement of VR video transmission. In our proposed scheme, expanding window fountain (EWF) codes is introduced to protect the Field of View (FOV) of VR video by sacrificing the quality of non-FOV. Under the same bandwidth conditions, this UEP method can improve the video quality of FOVs where users actually watching. By adjusting the window selection probability of EWF codes, we discuss the optimal degree of protection for the FOV. Moreover, to better evaluate the quality of VR video, we define a new metric called VP-PSNR to measure the quality of VR video. According to the simulation results, under the packet loss network transmission condition, our UEP scheme can effectively improve the quality of VR video compared with traditional equal error protection (EEP) scheme.