Implicit-Selected Transform in Video Coding

Abstract

AVS-3 is an emerging next-generation video coding standard, in which the transform-coding plays an important role. This paper presents a method of Implicit-Selected Transform (IST) to further improve the transform-coding in AVS-3. With IST, two different types of separable transform cores are introduced to perform transform-coding on residual signals of blocks with intra-prediction. At the encoder side, the two types of transform cores are tested and selected according to a Rate-Distortion Optimization (RDO) criterion. Instead of signaling the selected transform type explicitly, the information is hidden into the Parity of the Number of Non-zero Coefficients (PNNC) of a transformed block. At the decoder side, the selection is implicitly determined by checking PNNC. Experimental results show that the proposed method can achieve 0.64% and 0.35% BD-rate savings on average under All-intra and Random-access configurations, respectively, with negligible decoding time changes. IST has been adopted into AVS-3.