| JCTVC-M0378 AHG5: Crosscheck of JCTVC-M0136 proposed by Canon [J. Kim (LG)] [late]
Tests matched, supports the method.
JCTVC-M0137 AHG5: Square transform deblocking for 4:2:2 [C. Rosewarne, M. Maeda (Canon)]
(Discussion chaired by D. Flynn.)
At the 12th JCT-VC meeting, square transforms were adopted for the rectangular blocks present in the chroma channels when the 4:2:2 chroma format is used. This adoption results in boundaries between the pairs of square transforms that are not deblocked. It is asserted that having transform boundaries in the design that are not deblocked is inconsistent with the 4:2:0 design and could lead to deblocking artefacts. This contribution introduces deblocking to the boundaries between the square transforms in chroma when the 4:2:2 chroma format is in use. The simulation results show 0.0%, 0.2% and 0.2% gains in luma and chroma for AI Main tier, 0.0%, 0.1% and 0.2% gains in luma and chroma for RA Main tier and 0.0%, 0.1% and 0.1% gains in luma and chroma for LB Main tier.
There was some support expressed for this method as it seems instinctively the right thing to do (deblocking is evaluated on most other transform edges, except some 4x4 ones), in essence it could be regarded as a bug fix. However, after the cross-checker confirmed that they could not see any difference between the anchor and the proposed method when conducting informal subjective viewing, it was remarked that we should leave the spec as is unless strong evidence can be provided that this is worthwhile (even if there is a minor BD-rate gain in chroma).
No action.
JCTVC-M0440 AHG5: Cross-check for M0137 [M. Naccari, M. Mrak, A. Gabriellini (BBC)] [late] [miss]
The cross-checker confirmed the results and after performing some informal viewing couldn't find any difference between the proposal and the anchor.
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