The Joint Collaborative Team on Video Coding (jct-vc) of itu-t wp3/16 and iso/iec jtc 1/ sc 29/ wg 11 held its tenth meeting during 11-20 July 2012 at the City Conference Centre (ccc), a k. a

JCTVC-J0296 Cross-check of SAO on/off flags coding in JCTVC-J0269 [W.-S. Kim, D.-K. Kwon (TI)] [late]
JCTVC-J0140 AhG6: SAO Complexity Reduction with SAO LCU Flag Coding [W.-S. Kim, D.-K. Kwon (TI)]

As the current SAO syntax in HM-7.0 was originally designed considering quad-tree partitioning, it is asserted that it is not well structured for LCU based signalling. In this contribution, a new syntax structure for SAO is proposed, where SAO off is decoupled from SAO type, and SAO merge flags are removed. It is asserted that the complexity is decreased by reducing the number of context coded bins. At the same time, the coding gain is reportedly achieved by 0.6/0.2/0.1% for LCU size of 16/32/64 for Y (Main) when SAO LCU flag coding is used with removal of merge flags. When only merge up flag is removed with SAO LCU flag coding, the coding gain is reported as 0.7/0.4/0.2% for LCU size of 16/32/64 for Y (Main).

Different versions are presented with total removing of merge, only removing merge up, etc. Even in the simplest method which entirely removes merge, to use the method with SAO LCU flag, three contexts and 4 context coded bins are necessary (which may be more than in some of the other simplified solutions that are discussed).

Draft text is not provided for the version that entirely removes merge.

Some discussion whether the removal of merge would be a substantial benefit in terms of implementation and buffer saving; in particular merge left is regarded to be less critical. It is seen as an advantage that it would reduce the dependencies across tile boundaries.

Supported by one company other than proponents, several concerns expressed – no action.