Region-classification-based rate control for flicker suppression of I-frames in HEVC

In High Efficiency Video Coding (HEVC), the coding efficiency of I-frames is lower than P-frames and B-frames, which will cause the flicker artifact, especially in low bitrates applications. We propose a region-classification-based rate control for Coding Tree Units (CTUs) in I-frames to improve the reconstructed quality of I-frames to suppress the flicker artifact. The CTUs in I-frame are classified into three regions according to their motion vectors and complexity. When the bit budget of one I-frame is used up, the target bitrates for the remaining CTUs will be adjusted according to the regions they belong to, and the pixel-based unified rate-quantization (URQ) model is then used to calculate the QPs. Experimental results demonstrate that the proposed scheme can efficiently suppress the flicker artifacts and improve both the subjective and objective video quality when compared with the original scheme in HM9.0.