当目标码率较低时，在编码视频序列中周期性地插入I帧，会导致重建视频播放时出现“闪烁”现象. 为提高I帧重建质量，抑制“闪烁”，提出了一种基于URQ模型的I帧码率控制算法. 首先根据图像的运动趋势和复杂度将I帧划分为运动区域、图像复杂区域和平坦区域；然后依据人眼视觉系统对不同区域“闪烁”的敏感性，为视觉敏感区域分配更多的码率，其他区域分配较少码率；最后，利用URQ模型计算编码所需的量化参数值，实现对I帧的码率控制. 实验结果表明，所提算法能够在保证码率控制精度的前提下，有效抑制由于周期性插入I帧导致的视频“闪烁”现象，提高重建视频的整体主客观质量.
In high efficiency video coding, the coding efficiency of I-frames is lower than P-frames and B-frames, causing flicker artifacts, especially in low bitrates applications. We propose a rate control algorithm for I-frames based on URQ model to improve the reconstruction quality of I-frames to suppress flicker artifacts. An I-frame is classified into three regions according to their motion vectors and complexity, termed motion region, texture-rich region and smooth region. According to different sensitivities of human visual system to different regions, visually sensitive regions are allocated more target bits. The URQ model is used to calculate QPs. Experimental results demonstrate that the proposed algorithm can efficiently suppress flicker artifacts and improve subjective and objective quality of the video.
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