Refining QP to improve coding efficiency in AVS

This paper presents a Lagrange multiplier determination method and Quantization Parameter (QP) refinement algorithm used in the Rate-Distortion Optimization (RDO) process to improve the coding efficiency for Audio Video Coding Standard (AVS) (IEEE 1857). This paper investigates the Lagrange multiplier setting problem for different kinds of pictures in the encoding process of AVS. When Lagrange multiplier is determined, to minimize the RD (Rate-Distortion) cost, the optimal QP can be selected by multiple-QP optimization. However, this kind of optimization increases the encoding time significantly. This paper analyzes the relationship between the QP value and Lagrange multiplier in this paper. And then this relationship is applied in the encoding process of AVS to refine the predetermined QP value. The experimental results show that proposed algorithm can lead to significant bit saving compared with the default anchor of AVS. The proposed method improves the coding efficiency without increasing the processing time.