JVET-AG0064 AHG12: On Context modelling in Chroma Coefficient Coding [L. Xu, H. Yu, Y. Yu, D. Wang (OPPO)]

This contribution proposes to use the same and consistent spatial neighbors to derive context model index and Rice parameter for the chroma blocks not coded by LFNST or NSPT. The proposed method is implemented on the ECM-11.0 software.

The simulation results of the proposed method under CTC are shown as follows,

RA: -0.00% (Y), -0.02% (U), -0.04% (V)

The simulation results of the proposed method when DualITree=0 are shown as follows,

AI: 0.01%(Y), -0.22%(U), -0.18%(V)

The proposed modification only affects single tree, and is not applicable to dual tree.

Cross checker (also original proponent of JVET-AE0102) confirmed the results.

It was commented that the performance difference due to the proposed modification is negilible in the context of the current stage of exploration.

It was commented that making the proposed modification could also make certain aspects “more complex”.

No action at this stage.