基于复杂度HEVC码率控制的算法优化

Algorithm optimization based on the complexity of HEVC rate control

针对视频编码标准HEVC(high efficiency video coding)在编码过程中复杂度较高的帧层带宽相对不足而复杂度较低的帧层带宽相对富余之一的问题,为了降低计算复杂度,提高编码质量,本文首先通过研究复杂度在帧层编码过程中对码率分配的影响,提出了由SATD(sum of absolute transformed difference)构建复杂度模型,根据视频内容每帧的复杂程度,通过复杂度模型对帧层进行合理的比特分配。为了建立R-Q曲线,结合最大编码单元(LCU,largest coding unit)层的编码树特点,根据LCU残差信号的混合高斯分布特性进行量化参数(QP)的计算,从而使得输出码率与目标比特相等的同时尽可能提高视频质量。实验结果表明,所提出的算法比HEVC现行码率控制算法性能更加优良并且具有较强的鲁棒性,码率误差在0.01%以内,PSNR增益平均可达0.21dB。

The rate control mechanism of high efficiency video coding （HEVC） is using the average of the bandwidth in frame layer,rather than adjusing the target bits according to the complexity of the current video, which makes the encoding process of high complexity frame layers＇ bandwidth insufficient relatively,while the complexity of the lower frame layers＇ bandwidth surplus relatively. To solve those problems, in order to reduce the computational complexity and improve the quality of coding, firstly, this paper has researched the effect of complexity in the process of coding frame layer on the rate allocation. According to the complexity of the video content per frame,it allocates bits by the frame layer complexity model reasonably. Secondly,in order to establish R-Q curve, it combines the largest coding unit （LCU） tree characteristics and the Gaussian mixture distribution characteristics of the LCUJsresidual signal to calculate parameters, so as to make the output bit rate equal to the target bits. Experimental results demonstrate that the proposed method is better than HEVCIs rate control algorithm and it is of better performance and strong robustness,the rate of error is in 0. 01% and the average peak signal-to-noise ratio （PSNR） is up to 0. 21 dB.