Research On Video Error Concealment And Transmission Control Strategy Based On3G Networks

With the rapid development of wireless network communication technology andintelligent mobile phone, how to rapidly and efficiently transmit video data has become acore part of mobile phone application development in3G networks. But because of thewireless channel has high error rate, high packet loss rate, and the bandwidth is not stable,transmission is inevitable to face the high packet loss problem in3G networks. If you usethe TCP protocol to ensure reliable data transmission, it will bring large transmissiondelay. Based on the characteristics of video transmission, this paper studies videotransmission and video decoding error concealment technologies these two aspects. It hashigh theoretical significance and application value.According to the characteristics of3G networks video transmission, this paperproposes a real-time video transmission method based on improved UDT protocol. UDTprotocol is a reliable transport protocol which is based on UDP. Using this protocoltransfers video data will cause large delay. In order to solve this problem, this strategy ondata transmission and retransmission are improved in this paper. The improved UDTprotocol uses packet survival threshold. If the survival time of data packet is larger thanthe survival threshold,this data packet will not be send or retransmitted If I frames is lost,a GOP data belongs to the I frame cannot be decoded. This paper based on thecharacteristics of video codec, judge the sender whether to drop the I-frame data. If theI-frame packets being discarded, a GOP sequence of this I-frame will not be transmitted,until the next I-frame arrived. The improved UDT protocol effectively control videotransmission’s survival. In good network condition, the lost data packet will beretransmitted as much as possible. After I frame packets are discarded, we did not sendthe follow-up packet data, the data transmission overhead can be saved.Binding with the error concealment algorithm of ffmepg decoding library, this paperproposes an improved error concealment algorithm of P frame under ffmpeg. Ffmpegdecoding library uses the BMA error concealment algorithm to restored the damagedmacroblock. Although using BMA algorithm to recover the image sequence whichmotion is not very dramatic scene change not obviously has better effect. But if the scene changes rapidly, error images which are recovered by BMA algorithm will appeardislocation. In order to solve this problem, this paper proposes an improved ffmpeg errorconcealment algorithm. This algorithm uses the P frame’s intra macroblock number andthe motion vector of the block around the damaged macroblock to judge if the frame’smacroblock motion fierce is too large or scene changes rapidly. If the frame’s macroblockmotion fierce is too large or scene changes rapidly, using the spatial error concealmentalgorithm to recover the image, else using the BMA error concealment algorithm torecover the image. To achieve that, for error concealment using this algorithm in imagecampaign or scene change’s situation, its recovery effect is better than the BMAalgorithm. If the movement is not obvious or there is no scene transformation, theirrecovery effect similarity.Through the study on this two directions, it makes real-time video communicationby mobile phone on the3G networks more suitable with the characteristics of3Gnetworks transmission and video decoding display quality more excellent.