Joint Source And Channel Coding Based On LDPC And H.264

With the rapid development of mobile multimedia technology, the demands ofpeople for the wireless video communication are increasing. On the one hand, the videoinformation is compressed into bit streams and the correlation between the bit streams isvery small. On the other hand, the bandwidth resources of wireless channel are limited,and the bit error rate in the wireless channel is very high. There are a lot of problems inthe transmission of video information via the wireless channel.In terms of the sensitivity of video data streams to the channel, this thesis firstlypresents an Unequal Error Protection (UEP) scheme for video transmission, and thenproposes a Joint Source-Channel Coding (JSCC) scheme based on LDPC Codes andH.264. The experimental results show that the JSCC scheme can improve the reliabilityof video communication system, reduce the influence on reconstructed video qualityand system delay. The main contents and innovation are as follows:(1) Based on LLR BP and UMP BP-based decoding algorithm, an improveddecoding algorithm is proposed, which adjusts the iterative update of variable nodes byadding an offset factor in the variable node processing of the LDPC decoding process.From the simulation, we can draw the conclusion that the improved decoding algorithmgets a good trade-off between performance and complexity comparing the traditionaldecoding algorithms.(2) The performance analysis of the H.264code streams in wireless channeltransmission is finished. The simulation shows that the service quality is still unable tobe guaranteed due to the characteristics of the wireless channel although the H.264hasthe high compression efficiency. It is necessary to design a more efficient encodingscheme, such that the encoded bit streams can adapt to the variation of channel andimprove the performance of wireless video transmission.(3) Considering the different bits of video information on the effects ofreconstructed video quality, an UEP method based on the LDPC code is presented. It is an unequal error protection method that the different encoding strategies and thedifferent channel coding method are adopted according to the different importancelevels of video data streams. The simulation shows that the UEP scheme is much betterthan the equal error protection (EEP) scheme.(4) In view of the resources in actual communication environment are limited, aJSCC strategy is implemented by using the UEP strategy and adjusting source encodingparameters. The simulation shows that the JSCC scheme is an effective method in thevideo transmission, especially in poor channel conditions. It can not only effectively usethe limited bandwidth channel resources but also ensure the reliable transmission ofvideo information. The JSCC can achieve the optimal system performance by adjustingthe parameters of source coding and channel coding.