QP refinement according to Lagrange multiplier for High Efficiency Video Coding

This paper presents a Quantization Parameter (QP) refinement algorithm used in Rate-Distortion Optimization (RDO) process to improve the coding efficiency for High Efficiency Video Coding (HEVC). To minimize the RD cost, QP is one of the parameters that can be optimized. Usually, multiple-QP optimization can be applied to choose the best QP value. However, this kind of optimization increases the encoding complexity significantly. We analyze the relationship between the QP value and Lagrange multiplier in this paper firstly. And then we apply the relationship between QP and Lagrange multiplier to the encoding process of HEVC. The proposed QP refinement method has already been adopted into HM (the HEVC reference software). The experimental results show that proposed algorithm can achieve about 1.4%~1.9% bit saving for luma component on average compared with the default anchor of HM-8.0. The bit saving on chroma components are larger than that of luma. The proposed method improves the coding efficiency without increasing the processing time.