Implicit Seleted Transform Skip Method For Avs3

Abstract

AVS3 is an emerging video coding standard, and screen content coding is a very important feature of AVS3. This paper presents a method of Implicit-Selected Transform Skip (ISTS) to further improve the screen content coding performance. With ISTS, transform skip mode is introduced as an optional substitution to transform-coding on residual signals of blocks with intra-prediction. The indication of whether to apply transform skip is hidden into the Parity of the Number of Non-zero Coefficients (PNNC) of a residual block, instead of being signaled to the decoder. Moreover, the coefficients of an intra-coded block are reordered to make the coefficients more compact. Experimental results show that the proposed method can achieve 12.04%, 8.15% and 10.19% BD-rate savings on average under All Intra (AI), Low Delay (LD) and Random Access (RA) configurations, respectively, with the encoding time reduced by 5% to 8%. ISTS has been adopted into AVS3.

Enhanced Intra String Copy for Screen Content Coding in AVS3

“…Based on the observation and minimum entropy principle, value range C is divided into multiple subranges for optimal coding and binarization. For the string lengths of Evs and Ups, there are eleven subranges, which are the intersection of C and [0,1), [1,2), [2,4), [4,8), [8,16), [16,32), [32,64), [64,128), [128,256), [256,512), and [512,1024), respectively, that is,…”

“…On the other hand, for the string length of Ubvs, there are ten subranges: the intersection of C and [0,2), [2,4), [4,8), [8,16), [16,32), [32,64)…”

“…Five main SCC tools have been adopted in VVC [2]: transform skip residual coding, block-based differential pulse-code modulation (BDPCM), intra-block copy (IBC), adaptive color transform (ACT), and palette. In AVS3, five main SCC tools have been adopted in the draft [5]: IBC [6], frequency-based intra-mode coding (FIMC) [7], implicit selection of transform skip (ISTS) [8], adaptive control of deblocking type (ACDT) [9], and intra string copy (ISC) [10]- [12].…”