Perceptual Quality Consistency Oriented CTU Level Rate Control for HEVC Intra Coding
Guoqing Xiang, Xinfeng Zhang, Xiaofeng Huang, Fan Yang, Chuang Zhu, Huizhu Jia, Xiaodong Xie
Abstract
Rate control is an important technique for practical video coding applications by allocating suitable quantization parameters (QPs) for CTUs or frames to satisfy bandwidth requirement. However, rate control may result in video quality fluctuation because neighboring regions are quantized into different quality levels, which may affect viewing experience seriously, especially at low bitrate scenarios. In this paper, we propose a novel CTU (Coding Tree Unit) level rate control approach for intra frame of the high efficiency video coding (HEVC) standard with consistent perceptual quality. In particular, a new perceptual hyperbolic rate distortion (R-D) optimization method is proposed for rate control with the constraint of constant perceptual quality, which shows good compatibility with other R-D models. Herein, a novel CTU level perceptual distortion model is presented to achieve the optimal rate control of intra frames for HEVC, where the Lagrange multiplier is adjusted by taking advantage of the different perceptual characteristics to achieve the minimal perceptual distortion variation across CTUs within one frame. Extensive experiments prove that the proposed algorithm outperforms the state-of-the-art CTU level rate control methods by considering R-D performance. In addition, subjective simulation results demonstrate that our algorithm further improves the visual quality of compressed videos by reducing perceptual quality fluctuation.