中文摘要：

针对H．264编码方案，提出了一种实时的无需二次编码的低码率宏块级码率控制策略。为克服H．264码率控制模型的缺陷，首先提出了平均像素信息比特（APIB）的概念及其码率控制模型；然后在宏块层，根据各个宏块不同的编码复杂度进行准确的码字分配；接着通过APIB的变化来自适应地更新码率控制模型的系数；最后提出了完整的基于宏块的码率控制算法，并将其在JVT的JM85平台上实现。试验结果表明，与H．264中的码率控制算法JVT-G012相比，该算法不仅在控制精度上平均提高了0．171kbps，而且峰值信噪比平均提高了0．227dB，同时还较好地控制了输出码率和峰值信噪比的波动。

英文摘要：

A real-time single-pass bit rate control algorithm in low bit-rate of macro-block layer for H. 264 is presented. In order to solve the drawback of rate control model in H. 264, a new concept of average pixel information bit （APIB） and the novel rate control model based on it are represented at first; then the more precise bit allocation scheme is implemented according to the coding complexity of each macro-block, and the parameters of rate control model are updated by the change of APIB adaptively; finally, the complete rate Control algorithm is proposed. This algorithm is implemented in JM85 （ H. 264/ AVC）, the experimental results show that, compared to JVT-G012 in H. 264, the proposed method gains 0. 171kbps in control precision and 0.227dB in PSNR averagely, and controls the fluctuation on bit and PSNR precisely at the same time.