Video coding optimization in AVS2

Chinese second generation of the Audio Video Coding Standard, known as the AVS2, competing with HEVC/H.265 and AV1, has become a well-known video compression standard. Many unique tools have been developed and incorporated in AVS2. This paper proposes several encoder optimization schemes with respect to rate-distortion optimization (RDO). Specifically, by exploiting the close relationship between the total number of referenced pictures and the hierarchy of reference structure, a reference structure determined parameter (RSDP) algorithm reallocates Lagrange multiplier. Moreover, an adaptive quantization parameter offset (AQPO) algorithm is provided at both picture-level and Groups of Pictures (GoP)-level to adjust quantization parameters adaptively on top of the preassigned ones. Both RSDP algorithm and AQPO algorithm have already been adopted by AVS2 and incorporated in its reference software. Experimental results show that in the low-delay, RSDP and AQPO achieved savings of 1.35% and 1.26% on BDBR, respectively. • A frame level QP and λ allocation named reference structure determined parameter (RSDP) algorithm is proposed to satisfy GoP length 4, 8, and 16 respectively. • A GoP level QP and λ allocation named adaptive quantization parameter offset (AQPO) algorithm is proposed to deal with low-delay configuration. • Both RSDP and AQPO algorithms have achieved remarkable coding performance under BD-rate statistic units.