The Research Of The Application Layer Fec In Wireless Video Transmission

With the rapid development of the Internet and the large scale deployment of the wireless networks, developing multimedia services including images, video and data in the wireless channel or network has received more and more attention and become a theoretical research focus. Image and video is a body of the multimedia information and their data are highly compressed bit stream. The transmission environment of the wireless channel is very poor. For example, the time variability is very strong, and the bit error rate is high due to the influence of factors such as fading, noise. Besides, the bandwidth resource of the wireless channel is also very limited. Therefore, to provide high-quality images or video transmission in wireless channel environment faces a severe test.In order to overcome the above-mentioned problems, this paper studies the problems faced by the video transmission in the high bit error rate wireless channel. The combination of the video source compression coding and the application layer forward error correction coding should be considered.We do unequal error protection for the source compression coding information with different degree of importance so that it is possible to try to improve the quality of the reconstructed video in the case of the limited system resources. In order to achieve this purpose, this paper briefly describes the H.264/AVC video coding standard at first, and then establishes the importance level matrix of the MB based on motion vector on the basis of this standard. Secondly, this paper focuses on the wireless channel loss model, and the author proves the accuracy of the modeling of the wireless channel loss model using first order Markov model through theoretical analysis and simulation. At last, this paper analyzes the rate control algorithm in wireless video transmission. Considering the additional number of bits introduced by the application layer forward error correction, therefore, find the optimal quantization step which will be used by the source coding based on the end-to-end rate-control model with the Lagrange factor at first. Then we can obtain the source coding bit number and the application layer forward error correction encoding bit number, and we calculate the number of parity bits which will be joined in the different importance slice groups. Finally, this paper proposes a joint source coding and application layer error correction UEP plan based on the analysis and the results of the above three points.Simulation results show that the application layer UEP plan proposed by this article can get better video reception quality in the environment of narrow network bandwidth and high packet loss rate compared with equal error correction plan. The plan will also further improve the performance with network conditions becoming better.