一种基于Cauchy分布的H.264宏块层码率控制算法

提出了一种精确有效的H．264宏块层码率控制算法。首先，基于H．264编码器中DCT系数服从Cauchy分布的假设推导得出H．264宏块层的码率模型；并采用线性模型利用前一帧已知的失真度和量化参数值对失真度进行预测；最后，在宏块层通过Lagrange方法最小化失真度，确定宏块的量化参数。实验结果显示，与JM8．6中采用的码率控制算法相比，本文算法不仅能提高平均PSNR，而且能显著降低比特数估计偏差，从而提高图像质量，减小比特数波动，更好地跟踪目标码率。

Macroblock layer rate control algorithm for H.264 based on Cauchy distribution

An accurate and efficient macroblock layer rate control algorithm was proposed for H.264.Based on the assumption that the distribution of DCT coefficients in H.264 encoder follows Cauchy distribution,a macroblock layer bit rate model was derived.Then,the distortion was predicted by a linear model using the actual distortion and the quantization parameters(QP)of the previous frame.At last,Lagrange method was used to minimize the distortion and determine QP of macroblocks.Experimental results show that the proposed rate control algorithm can provide higher average PSNR,and significantly decrease bit estimation error,compared with JM8.6 rate control algorithm.Therefore,our algorithm can improve the image quality,reduce the bit fluctuation and match target bit rate more accurately