R-Lambda model based CTU-level rate control for intra frames in HEVC

In High Efficiency Video Coding (HEVC), the coding efficiency of intra frames is much lower than inter frames. If the bits allocated to intra frames are not sufficient to improve their quality, the quality fluctuation between intra frames and their neighboring inter frames will appear. But if too many bits are allocated to intra frames, the other frames may get bits starvation, which will cause quality degradation of some other frames. We propose an R-Lambda model based CTU-level rate control to improve the reconstructed quality of intra frames with fewer bits. CTUs in intra frame are classified into three regions according to their motion vectors and complexity. The bits allocated to CTUs belong to different regions will be adjusted and the R-lambda model will be used to calculate the QPs. Experimental results demonstrate that the proposed rate control can efficiently reduce the bits cost by intra frames and suppress the quality fluctuation between intra frames and others when compared to the rate control by R-lambda model adopted in HM10.0.