Rate Control Algorithm For H.264/AVC

As the main carrier of the visual information, Video image which compared with voice and text messages has a large amount of information, intuitive, vivid and exact characteristics. So it has broader applicability and greater efficiency in the use, and has a profound impact on people’s life and work. In case of limited bandwidth and storage capacity, to solve the problem has become the key to the application of video image data compression, which video images has massive information. As a new video coding standard, H.264/AVC becomes the most important video coding standard, because it has a superior compression performance and a good network of affinity. Rate control is an essential component in the video communication system applications; it has a direct impact on the quality of the image encoding. JVT-G012algorithm is currently the mainstream of the H.264/AVC rate control algorithm, although it is a good solution to the hens paradox, there are some shortcomings. According to the shortcomings of JVT-G012’frame layer and basic unit layer rate control algorithm, this paper presents a corresponding improvement algorithm as below:.1、Rate Control Algorithm for H.264with Comprehensive Factor:In the JVT-G012algorithm the uncoded P frame is calculated by the equal division of bits, neglects the position of the P in the GOP and the information of already coded frame. So this paper offers a new algorithm. Firstly, the target bits allocation should be modulated according to the multi-stress composed by the complexity of the P frame and the position of the P in the GOP. Then, modulate the current coding frame’s evaluation parameters according to the already coding frame. As shown in experiments, compared with JVT-G012algorithm, the proposed algorithm in this paper can improve the quality of the video image especially when the movement becomes severe or the texture is complex, it can also achieve an output of the actual code rate closer to the target bits.2、Rate Control Algorithm for H.264with image complexity factor:For the purpose of signal well. Solving the problem of JVT-G012rate control algorithm distributing bits evenly for P frames, JVT-G012algorithm didn’t consider the complexity of the P-frames. So this paper presents a new bit rate control algorithm, which uses the frame difference ratio to allocate target bits and utilizes the currentbufferfullness to adjust the current quantization parameter. A large number of experimental results show that the proposed algorithm, in comparison to the JVT-G012algorithm, not only controls the bit rate much precisely, but also improves the image quality.3、Basic Unit Layer Rate Control Algorithm for H.264\AVC Based on Human Visual System:In the JVT-G012algorithm of H.264, each pixel are treated equally and the influence of human visual characteristic in basic unit layer rate control has not been taken into account, resulting in the low image quality. This paper takes the influence of human visual characteristic into full consideration and offers ways to improve the subjective quality of image, that is, using the visual characteristic factor which is constituted by the motion feature and edge feature to reasonably allocate the target bits, then adjusting QP. Large numbers of simulating experiments show that, compared with JVT-G012algorithm, the proposed algorithm can not only control the bit rate more accurately but also make the PSNR wave stable, so as to improve the stationarity of the video image.