基于运动估计的H.264/AVC BU层码率控制算法

Motion estimation-based basic unit level rate control for H.264/AVC

为解决H.264/AVC视频编码标准中码率预测不准确的问题,基于JM80提出了一种改进的BU层码率控制算法。该算法假设编码复杂度均匀分布在图像宏块的每个点上,根据宏块运动矢量预测出下一帧的编码复杂度,进而预测出宏块的量化步长和输出比特数的关系,因而比JM80采用的模型更直接和准确。该算法同时采用基于Lagrange乘子法的率失真最优准则的比特分配策略。仿真结果显示出经该算法控制后的输出码率非常接近目标码率,且和JM80中方法相比,对所有测试序列都有明显的峰值信噪比(PSNR)增益。

A new basic unit level rate control algorithm for H. 264/AVC video coding build on the JM80 framework gives more accurate, direct motion-based rate prediction than in JM80. In the algorithm, the encoding complexity of the next frame is predicted from the current frame based on the assumption that each pixel consumes the same computational effort. The result relates the quantitative stepsize and output number of bits. The bit allocation scheme is then rate-distortion optimized using the Lagrange method. Tests show that the algorithm accurately meets the target bit rate. The algorithm achieves considerable peak signal to noise ratio （PSNR） improvement for all test scenarios compared with the JM80 algorithm.