Based Wireless H.264 Rate Control And Error Concealment

As electronic and communication technology developing, the traditional voice and message services have been unable to meet the people's daily needs. The emerging video and audio communication business is gradually infiltrated into the daily work, life, entertainment and even security fields. Therefore, video compression and transmission technologies are concentrated by academia and industry closely. Currently, H.264 is the latest video compression standards on the market. And its compression performance, code quality, and network adaptability has been phased progressing, it is possible to occupy the dominant position in the various areas of applications. This paper concentrate the wireless communications, video coding and transmission and so on several key technologies depthly, especially the rate control in encoding process and the error concealment in the decoding process , then simulate the test.The limited bandwidth and network emergencies in wireless communications, lead to control the encoded bit stream. Therefore, it needs a rate control system as accurately as possible for ensuring smooth video transmission, efficient channel utilization and to meet the quality of the video that the user needs. H.264 standard using a variety of encoding methods or tools to improve coding efficiency, however, the rate control is not good enough. H.264 decoder provides a range of fault-tolerant tools, but their utilization are very low, only using a single or even not these tools, so it impossible to obtain the best video quality.In the paper, the first is to introduce the research background and research purposes. Then introduce video compression coding theory and the existing video compression standards briefly, especially in the coding techniques and application objectives. Make an overview of the wireless communication systems, which analysising the wireless communications features, establishing channel models and building the entire wireless video communication system. Then analyze the principles of rate control, introduce several classical comparison of rate control algorithm, recomend JVT-G012 proposal for H.264 rate control, analyze the technologies'strengths and weaknesses. The paper presents a improved frame layer rate control algorithm. The algorithm is to propose a new index model for revised P-frame quantization parameter, and optimize the target number of bits allocation according to the different complexity of video images. The experimental results show that the algorithm can effectively improve the PSNR values, make video results smoothly, the buffer level maintain within a certain range and reduce frame skipping. Then analyzes the wireless network-friendly based on H.264, which can help to propose a H.264 rate control and error concealment methods based on wireless. The method is to propose a method of calculating the initial QP values more accurately and the prediction method using the space or time correlation to predict the mean absolute deviation and target bit allocation program more accurately. After transmise by the package, then decode in the decoder, where using an adaptive error concealment algorithm, adaptive selection mask tool by the data lost and coding features,. The experimental results show that the method using in wireless network, can effectively improve the video quality, reduce frame-skipping, even smooth the video output.