在H．264中，对于一个宏块行，ρ与比特率仍然满足线性关系。基于此，提出了基于ρ域源模型的H．264宏块行层码率控制算法。在宏块行间，根据第一次RDO时各个宏块行所耗用比特数的百分比来分配比特数。实验结果表明，与JM8．4中采用的码率控制算法相比，本文提出的宏块行层码率控制算法在保证基本相同的编码效率情况下，能显著降低比特数估计偏差，更好地跟踪目标码率。

Extensive experimental results show that p is still linear with the bit rate of a macroblock slice in H.264 via p-domain source modeling. The bit allocation of the proposed method is achived according to the percentage of bit count of each macroblock slice in the first RDO. Experimental results show that the proposed rate control algorithm can guarantee the same coding efficiency, achieve significantly smaller bit rate estimation error and be better matched to the target bit rate than JM8.4 rate control algorithm.