Research And Realization Of H.264 Rate Control In Real-time Video Coding And Transmission System

In the past few decades, video communication becomes true since the rapid development of video compression and transmission technology. As a standard made up by ITU and ISO/IEC, H.264 gets high performance in compression and works excellently in transmission. Video phone based on H.264 has been selling in the market, which illustrates the importance and extensive use of H.264. With the development of wireless transmission technology, the research of real-time video transmission becomes a hotspot, which pushes the improvement of rate control technology. Rate control is a technology which could subject the bit rate to a constraint value to fit the channel bandwidth. In Entertainment, people's requirements for the video system are often high-definition and lifelike visual effects. While in the industrial and military applications, real-time performance and stability are more important, often. This design originates from a co-operation project with some scientific research unit, a real-time video compression and transmission system which has high requirement in real-time performance. A rate control schme is needed to be designed.First of all, the paper presents a detailed analysis of key algorithms in H.264 principle by researching a lot of literature, and discusses the design of the video compression system based on DSP, including the bottom-chip peripherals driver programming, transplantation of T264 source code and the DSP realization and optimizing. Then, the bit stream of H.264 is analyzed, and the robustness via wireless transmission is also discussed. Based on the discussion, this design used two kinds of error resilience method, fixed parameters and redundant slice, for the system.The emphasis of the paper is the research and realization of the rate control algorithm. After researching a lot of literature, several rate control models are analyzed, both the advantage and disadvantage.Compared with the former video coding standard, H.264 brought in the theory of rate distortion optimization, which lead to The Chicken and Egg Dilemma. So the conventional rate control schme need to be modified. The paper shows how the dilemma was solved in H.264 rate control scheme, analyzes the development and shortcomings in different schemes and then discusses several classical improved methods. The paper uses the framework of H.264 rate control scheme JVT-G012, and proposed a low complexity rate control algorithm in MB-layer. Making use of temporal and spatial correlation among frame, a temporal-spatial method to predict the MAD combining with motion vector is proposed.Using linear modes instead of secondary model reduces the computational complexity much. Using the information of coded MB to adjust the current MB's quantization parameter makes the rate control more effectively.In bit allocation of frame level, by amending the conventional regulation of target buffer level, the bit allocation becomes more reasonable, and the standard deviation of PSNR is significantly improved.