由于JVT G012在基本单元层采用线性预测MAD的方法，且使用相同的QP量化，带来运算量大且不够精确的问题。为此，提出一种基于基本单元层码率控制的改进算法。首先，用时空加权模型来预测MAD；然后，采用宏块层码率控制策略来分配目标比特；最后，依然采用JVT G012中的二次R Q模型计算QP。仿真结果显示，采用改进算法的H264编码器，在取得更低比特率的同时，有效地提高了PSNR。

Because a linear model is usually used to predict the MAD and the QP quantization is the same in the JVT G012, which costs too much in operation and cant avoid deviation, an improved rate control algorithm for the basic unit layer enconder is presented. Firstly, the MAD is predicted by a new weighted time and space model. Secondly, macroblock layer rate control strategy is used to distribute target bits. Finally, the quadratic RQ model in the JVT G012 is still adopted to calculate QP. Simulation results show that the PSNR is effectively elevated and lower bit rate is achieved in the H.264 encoder by using the new algorithm.