Reverse scan for transform skip mode in HEVC codec
Vijay Bansal, Amit Kumar Chawla, Mahesh Narain Shukla · 2013
High Efficiency Video Coding (HEVC) is being developed by Joint Collaborative Team on Video Coding (JCTVC). HEVC has transform skip mode which is only applicable to 4×4 TUs (Transform Units). Transform process is skipped when this mode is selected. By introducing transform skip there is significant gain in coding efficiency for F class sequences [1][2]. In this paper it is proposed that before variable length encoding of the transform skip cases, reverse the scanning of the residual of 4×4 block sizes. Due to this modification it is observed that coding efficiency further increased on an average by 1.6% in terms of bd-rate [3] for class F sequences in all intra (AI) testing configurations. For other GOP structures like RA (random access), low delay with B pictures (LB), and low delay with P pictures (LP) average-bit-rate gains are 1.1%, 0.64% and 0.57% respectively. Due to this change there is a negligible impact on encoding/decoding time.