JVET-R0293 Fixes for 6-tap interpolation filtering for affine motion compensation [K. Andersson, R. Yu, Z. Zhang, J. Ström (Ericsson)]

It is asserted that the some of the current 6-tap interpolation filters for affine motion compensation have significant phase misalignments compared to the expected phases of the interpolation filters. This contribution proposes modifications of the filters for the fractional positions 4/16, 5/16, 6/16, 10/16, 11/16 and 12/16, and it is claimed that this fixes the phase misalignments of the current filters.

The modifications were reported to be tested under VTM-8.0 CTC. The impact on coding efficiency is reported to be -0.01%/-0.09% for RA/LDB. The modifications were reported to also be tested for the non-CTC) affine test set which was used to determine the performance of proposals in the past affine CEs. The impact on coding efficiency on that test set is reported to be -0.20% for RA.Presented Fri 17 April

It is mentioned that phase is less important in motion comp, amplitude/energy preservation more important. It is also mentioned that even the 8-tap filters are not optimum in phase. New results in v4 include the energy gain, which show that it is slightly lower for 6/16 filter than for the current filter, whereas for the other two (4/16 and 5/16) it is slightly higher.

It was also asked if the visual effect of the filters was investigated. The proponent says that no difference was visible.

No action (see further notes under JVET-R0292).