Research On Basic Unit Layer Rate Control Algorithm In Low Bit-rate For H.264/AVC

The ultimate goal of rate control is to transmit high quality video sequence under the limited buffer capacity and channel bandwidth.In both real-time video communications to meet requirements of low transmission delay, but also to ensure good video quality, so rate control plays a key role in H.264 protocol.After doing research on the standard of H.264 rate control algorithm,I did the follow reseach:1.To solve the issues of the chicken and egg dilemma of rate control model in JM86, the paper improves the calculation method of average pixels information bit (Average Pixel Information Bit, APIB) ,then use the improved average pixels information bit and the change of peak signal noise ratio (Peak Signal Noise Ratio, PSNR) of current macroblock to calculate complexity of the macroblock. The paper uses the complexity to allocate bit for each macroblock. The simulation results show that the improvement of the article not only in the rate control algorithm for improved accuracy, but the average peak signal noise ratio also improves by 0.15 dB.2. Scene change is bound to exist in the actual sequence of the video. In order to effectively determine the scene change, this article using different scene of the DCT of absolute terms coefficients of adjacent frames has the large difference, and within the same scene of the DCT absolute terms coefficients of adjacent frames changes in the characteristics of a smooth. In this paper,an algorithm is proposed.The algorithm is easy to accurately determine a given decision threshold, and detection accuracy is better.3.To deal with in the scene change frame, the first, the paper improves the distribution algorithm of buffer.When scene change occurs, it increases the difference of adjacent frames of the target buffer in accordance with image complexity, set each frame buffer to prevent buffer overflow or underflow. Then to improve the algorithm of allocating bit for each frame.That is, to allocate bit for the scene change frame, according to the distance from the switch frame.The improved bits adjustment factor is used to amend the bits that allocated to each frame. Simulation results show that the improved algorithm is effective.