Research And Improvement Of The Algorithm, Based On The H.264 Rate Control

Video, in which there are more rich in information, wieldier and more practicable, is widely applied in various fields. H.264 video coding standard is designed to give a new technical solution to a broad range of applications, such as from low bit rate and high error code video communication to high-bit-rate and low delay video broadcast, interactive video-on-demand services etc. So this standard attracts much attention from academic and industrial fields.Rate control is one of the key techniques of the video communications. It will directly affect the image quality in receiver. Because the complexity and motility of images are not same, it will lead to huge fluctuation of the output bits. It is necessary that fluctuation is controlled to a limited range by some rate control algorithms, so as to satisfies the demand of the real-time video communication. It is important to do the research for code rate control.Firstly, we introduce the development of the video coding standard, and discuss the key technique of H.264, including system composition, inter-prediction, intra-prediction, integer transform, entropy coding, rate distortion optimization and so on.Secondly, the mechanism of the rate control and information coding model is described. The classical rate control algorithm in the video coding standard is analyzed, and with a deep research on the rate control algorithm in H.264 JM8.6. Considering the shortcoming of H.264 rate control, we propose the modifications as follows: (l)In frame level bit assignment, the H.264 rate control algorithm averagely distributes to the other un-coded-frame of the GOP, has not considered the difference between the frames in the video sequence, this paper adopts the motion complexity to measure the movement activity of each frame, realizes frame level bit assignment according to the above method; (2) The rate control strategy of the basic unit used in H.264 had improved the entire rough frame control, but it had not considered the macro-block itself activity, the paper proposed a effective macro-block level code rate control algorithm from the spatial-temporal viewpoint. Simulations show in standard test video that this proposed arithmetic can control the code rate, meanwhile the quality of video also has been improved accordingly.