JVET-AC0124 Non-EE2: Bi-prediction with block-level only out-of-bound management [F. Le Léannec, M. Blestel, P. Andrivon, M. Radosavljević (Xiaomi)]

This contribution proposes to remove all sample-adaptive processes in the enhanced bi-prediction method of JVET-Z0136 used in ECM-7.0. Instead, a block-level management of out-of-bound (OOB) samples is proposed. No more sample-by-sample OOB criteria evaluation is used, and no more sample-adaptive bi-prediction is applied.

The proposed method reportedly leads to the following BD-rate performances over ECM-7.0 anchors.

RA: 0.00% / -0.01% / -0.08% (Y/Cb/Cr). Runtime: 101% (Enc), 102% (Dec)

LDB : -0.01% / 0.19% / 0.09% (Y/Cb/Cr). Runtime: 97% (Enc), 98% (Dec)

Partial results were confirmed by cross-checkers. One cross-checker suggested that the second aspect of the change (not applying BDOF offset in OOB subblocks) is unnecessary, and the current method of OOB handling could be retained.

It was commented that some aspects might be implementation dependent, e.g. the copying of the non-OOB content from the other reference picture.

Replacing the sample-level check by block-level check appears appropriate, but it was questioned if this might enforce superfluous subblock processing in some cases.

The benefit of this was not obvious, so no action was taken on it.