JVET-AK0186 Non-EE2: Subblock-based spatial MVP [Z. Deng, K. Zhang, N. Zhang, L. Zhao, Y. Wang, W. Yin, M. Salehifar, L. Zhang (Bytedance)]

This contribution proposes a method of subblock-based spatial MVP, in which the subblock motion field of the current CU can be inherited from the motion of spatial neighbour blocks. The impact on coding efficiency and runtime of the proposed method over ECM-15.0 are reported for {Y, U, V, EncT, DecT} as below:

RA: { -0.01%, -0.02%, 0.02%, 100.1%, 100.0% }

LDB: { -0.10%, -0.21%, -0.05%, 100.2%, 101.1% }

Only spatially adjacent neighbours are considered as additional candidates.

It was commented that other candidates could be used, however those might be more complicated than the proposed method which is simple and straightforward extension of SBTmVP

This had a reasonable tradeoff, with good gain for LDB. Several experts supported investigation in an EE. As a variant, it was suggested also to test using a zero MV if one of the neighbours is intra coded.