SAO filtering inside CTU loop for high efficiency video coding

In the HEVC standardization process, the In-loop filter module is added with a new video coding tool called sample adaptive offset (SAO). SAO is placed after de-blocking in video coding loop. The HM implementation (HM10.0, 2013) & the standard (Bross et al., 2013) indicates picture basis in-loop filtering i.e., both de-blocking and SAO. Although standard specifies picture basis de-blocking operation, it added a note indicating the possibility of CTU/CU level de-blocking execution. But there is no such mention of possibility for SAO execution at CTU/CU level. Standard explains about applying SAO filter on entire picture after reconstruction and de-blocking. But many-a-time, for the purpose of low-latency, better memory-bandwidth efficiency and cache performance, it is needed to implement SAO filter at CTU level for majority applications. As well, if any Hardware Accelerator (HWA)/ASIC to be developed for HEVC, all modules are very much expected to execute at CTU/CU level for better pipeline performance. This paper presents & discusses the possibility of bringing SAO at CTU level after de-blocking.