实时视频编码中的低复杂度码率控制算法设计

Low complexity rate control scheme for real-time video coding

针对H.264原有码率控制提案中的不足,并考虑到H.264实时编码对编码效率的要求,设计了低复杂度的宏块层码率控制方案。对于图像复杂度的预测,充分挖掘图像的时空相关性,结合运动矢量对MAD进行预测,将G012的MAD预测算法中线性回归的算法复杂度降低为加权平均的算法复杂度。对于率失真模型,采用运算复杂度低的线性拟合代替G012算法中的二次拟合,并结合SSIM讨论了这种简化的可能性。针对运动量大的图像编码后PSNR的波动问题,对GOP层初始QP确定和P帧比特分配进行了改进,并充分利用已编码单元信息对当前量化参数进行调整,有效的控制码率。实验证明,改进后的算法对平稳输出序列的PSNR波动和降低运算复杂度有比较好的效果。

Considering the deficiency of H.264 rate control scheme and the coding efficiency requirements for real-time encoding,a low complexity rate control algorithm in MB-layer is proposed..MAD is predicted by combining motion vector and the temporal and spatial correlation to reduce the complexity of G012-MAD prediction algorithm from linear regression to the complexity of the weighted average.For the rate-distortion model,the linear model with low computational complexity instead of the quadratic fitting algorithm in G012 is used,while the possibility of is discussed combining with SSIM.For the fluctuation of the PSNR of the coded image with large movement,the determination of QP in GOP layer and the bit allocation of P frame are improved,and the current quantization parameter is adjusted by making full use of the information of coded MBto control the rateeffectively.The experimental results show that the algorithm is more effective in resisting the fluctuation of PSNR for smoothly output sequence,and can decrease computational complexity.