Research And Implementation Of Panoramic Video Transmission System Based On DASH Transmission Technology

With the rapid development of the Internet and the continuous improvement of terminal software and hardware computing capabilities,the business related to Virtual Reality(VR)technology is expanding rapidly.As one of the forms of VR,panoramic video is due to its 360-degree viewing angle and high-resolution applied in various fields.While bringing a new visual experience,it is also bringing a huge increment of data.Guaranteeing video quality as much as possible under different network conditions and improving user Quality of Experience(QoE)have become a huge challenge for online panoramic video transmission.Panoramic video transmission system includes projection,video coding and data transmission.The selection of various solutions is closely related.This thesis is based on Equirectangular Projection(ERP)panoramic video,H.264 coding standards and Dynamic Adaptive Streaming over HTTP(DASH)transmission,the main work of this thesis is as follows:1.Aiming at the problem of use traditional coding strategy to reduce bitrate will get bad image quality,this thesis proposed a DASH-oriented panoramic video coding strategy.The video Temporal perceptual Information(TI)value is calculated through the two-frame difference algorithm,and different levels are divided according to the TI value.Classification and coding are performed according to the average TI value of the video and the number of different TI levels contained in the video.Experimental results show that,TI has a correlation with video quality under certain conditions,and this strategy improves the video quality under ERP and spherical projection compared with the traditional strategy in terms of image structure distortion.2.Based on the large difference in low bitrate image quality of different TI clips,for low bitrate hybrid TI video,a bitrate adaptive allocation strategy based on greedy algorithm is proposed to hierarchically coding different TI level clips in the video.Experimental results show that,compared with non-adaptive strategies,adaptive strategies improve video quality.3.This thesis build a panoramic video transmission system based on DASH,the structure is server/client mode.The server is used for panoramic video processing,slicing and storage,and the client is responsible for file request,throughput estimation,bitrate selection,and video playback.The server has added the coding strategy decision module to calculate the panoramic video TI value and feedback coding parameters.The method of calculating the average throughput based on historical throughput in the client is based on the exponentially weighted moving average method.Experimental results show that,this system can provide better user QoE than traditional DASH transmission systems.