一种HEVC低延时编码码率控制算法

传统码率控制方法常常引起视频编码器的率失真性能降底。为了在满足码率控制精度的同时改善编码器率失真性能,提出一种基于改进R-λ模型的帧级码率控制算法。根据帧率把待编码视频序列划分成多个控制单元,并为当前控制单元分配目标比特;根据控制单元层的可用比特数为当前GOP分配目标比特;根据GOP层的可用比特数为当前待编码帧分配目标比特,再利用改进的R-λ模型计算得到拉格朗日乘子λ进行编码。在通用测试条件下的实验结果显示,该算法具有较高的码率控制精度,同时改善了编码器的率失真性能。其平均码率相对误差为0.095%;以不开启码率控制的HM16.7作为基准,平均码率节省(BD-Rate)达到了2.6%。

RATE CONTROL FOR LOW DELAY CODING IN HEVC

Traditional rate control methods often cause degradation for the rate distortion performance of video coders. In order to improve rate distortion performace of encoder while meeting the accuracy of rate control, we proposed a frame-level rate control algorithm based on an improved R-λ model. The video sequence to be coded was divided into several control units according to the frame rate, and the target bits were allocated to the current control unit. Target bits were allocated according to the number of available bits in the control unit layer for the current GOP. Target bits were allocated according to the number of available bits in GOP layer for the current frame to be coded. We adopted the improved R-λ model to calculate the Lagrange multiplier λ for coding the current frame. Experiment was performed under the common test conditions. The test results show that the proposed method maintains high accuracy in bit rate control and achieves better rate-distortion performance. The relative error of the average bit rate is 0.095%. With HM16.7 anchor without rate control, the average bit rate saving (BD-Rate) reaches 2.6%.