Research And Implementation Of Video Coding And Transmission Quality Evaluation Based On Android Platform

With the increasing demand for video quality and subjective experience,more stress has been put on audio & video encoding and decoding in mobile phones,which results in the reduction of the overall computational performance.Therefore,more and more mobile phone manufacturers plan to embed the module of video & audio hardware coding phones,while still facing a common problem to use hardware coding module efficiently.At present,the evaluation standards of video transmission quality are also faced with some problems.With the video service becoming popular rapidly,the user experience of service has been paid more attention.From the user's point of view,they do not care about the network layer of the QoS,their concern is whether getting satisfactory services.Therefore,evaluation of video streaming services,from the perspective of the user QoE(Quality of Experience),is becoming increasingly important.To solve the above issues,an new solution is proposed based on the research of video streaming media transmission project in Android platform.First,this paper analyzes the process of the original YUV video frame acquisition and encoding from the lower layer software,and then refer to developers interfaces provided by the X264 open source project,this paper incorporates the Android Stagefright library encoding hardware facilities,encapsulates it into hardware interface,which is as easy as X264 encoding interface for users to use,in order to achieve encoding acceleration.Finally,it is verified by experiments that the hardware coding is more practical than the software coding in real-time video transmission in embedded devices.Second,after a analysis and comparison of PSNR/MoS evaluation,QoS/QoE model evaluation,MDI(Media Delivery Index,media streaming performance index)evaluation,MDI is chosed as evaluation algorithm when considering the project environment.Since the MLR(Media Loss Rate,the media packet loss rate)index of MDI only computes packet loss in general,this paper present designed a new RTP(Real-time Transport Protocol)protocol expansion head.This new head could distinguish calculation of packet loss among the I frame,P frame or B frame so that the MDI algorithm is more close to the principle of QoE.Finally,the experiment showed that the proposed MDI algorithm were more able to reflect the QoE video service experience when using MOS(Mean Opnion Score)score as the evaluation standard.