The Research On The Key Technology Of VNC Image Transmission

Virture Network Computing is an excellent remote control software.VNC has been widely used by its cross-platform,low bandwidth and easy to transplant and other characteristics.However,VNC has been in dealing with multimedia applications,especially in dealing with video applications.At first,this thesis analyzes the disadvantage of the VNC in the processing of video applications.And then,this thesis improves and implements the coding module and transmission mode in the VNC.The main work is as follows:Firstly,the research and implementation of video transmission in the VNC.This thesis presents hybrid transmission strategy.At first,the VNC screen update scheme is studied,and the VNC screen update area is acquired using the hierarchical update area detection algorithm.Thereafter,VNC judges whether the current frame is in the video mode according to the mode switching algorithm.If VNC is in the video mode,the current frame is encoded by H.264 and the encoded data is transmitted via RTP.If VNC is in non-video mode,the RFB protocol is used for data transfer.Secondly,in order to ensure that the flow can be successfully transmitted and make full use of network bandwidth,the thesis improve the X264 bit rate control,according to the characteristics of VNC acquisition screen.In this thesis,the X264 CRF + VBV mode is optimized after analyzing the rate control scheme of X264.In this thesis,frame rate control and macroblock rate control are optimized.In the frame rate control,the bit rate of the frame is increased by reducing the bit rate of the P frame,and the SKIP mode is selected as the optimum mode of the P frame under the specific conditions.In the macroblock-level bit rate control,the QP of the rapidly changing area improves the QP of the rapidly changing area,thereby improving the image quality of the non-video area.Finally,this thesis implements and validates the proposed scheme.This thesis uses FFmpeg as the H.264 codec.After the mode switch,transmission module and codec module in the VNC are implemented,the proposed VNC is tested.The test content includes functional testing and performance testing.The functional testing is mainly on the word to delete and other basic operations and video files to play,observe the status of VNC client.In addition,the VNC in the CPU usage,network bandwidth and other indicators and tight VNC contrast.After analyzing the results of the experiment,the VNC coding module uses the H.264 standard,which makes the VNC improve the CPU utilization at run time.On the whole,the optimized VNC in dealing with remote video applications,reducing the network bandwidth occupied,improving video playback fluency,improving the user's experience.