JVET-R0403 On the boundary strength derivation of IBC coded blocks [B. Ray, G. Van der Auwera, M. Karczewicz (Qualcomm)] [late]
When both sides of the boundary are IBC coded, the boundary strength derivation requires whether the difference between the vertical or horizontal components of the block vectors are greater or equal than 8 units of 1/16 luma samples. However, as IBC always uses integer pixel(s) block vector resolution, the condition can be corrected to check whether the block vectors are equal or not, thus the comparison with the threshold (8 units of 1/16 luma samples) can be avoided.
Reviewed Sun. 19 April.
This appears purely editorial, as IBC vectors are integer, and measuring them in 1/16 sample units appears unnecessary.
It is however noted that the BVs may be stored in units of 1/16 samples in the same memory as MVs. It is to be checked what the phrase “block vectors used in prediction” means. If the BVs described in the prediction process are expressed in 1/16 sample units, the change would be wrong.
Decision: Left to the discretion of editor to take action.