The Joint Collaborative Team on Video Coding (jct-vc) of itu-t wp3/16 and iso/iec jtc 1/ sc 29/ wg 11 held its tenth meeting during 11-20 July 2012 at the City Conference Centre (ccc), a k. a

JCTVC-J0523 Mental cross-check of JCTVC-J0122 solution 5 [Y. Takahashi, O. Nakagami, T. Suzuki (Sony)] [late]
JCTVC-J0524 Mental cross-check of JCTVC-J0122: AHG10: Hooks related to motion for the 3DV extension of HEVC [J. Boyce (Vidyo)] [late]
JCTVC-J0224 AHG10: Hook for scalable extensions: Signalling TMVP reference index in slice header [O. Bici, M. Hannuksela, K. Ugur (Nokia)]
JCTVC-J0505 AHG10: Mental cross-check of JCTVC-J0224 [Y.Chen(Qualcomm)] [late]
JCTVC-J0302 Restricted usage of motion vectors for long-term reference picture in motion vector prediction process [I.-K. Kim, Y. Park, J. H. Park (Samsung)]

[abstract cleanup]

In this contribution, two changes are proposed to the current design by marking motion vectors from LTRPs as unavailable instead of using it without scaling. The first solution is not to insert motion vectors into the candidate list by marking it unavailable if the motion vectors are from LTRPs. The motion vector predictor is marked as unavailable before the scaling process is performed. The asserted benefit of this approach is that by removing the inefficient motion vectors which are scaled or non-scaled motion vectors from LTRPs, more efficient motion vectors can be included in the list. The second solution change is that motion vectors are not inserted into the candidate list when the scaled motion vectors are asserted to be likely to be inefficient. In this solutionchange, the differentiation between LTRP and short-term reference picture (STRP) is not required. When POC difference (Tr) between reference picture of current PU and reference picture of candidate PU (co-located PU or neighbor PU) are larger than pre-determined threshold (THpoc_diff), motion vector scaling is not used. The motion vector predictor is marked as unavailable before the scaling process is performed. Both changes are applied to both spatial and temporal motion vector prediction. Although Aaverage coding efficiency gains from the second solution for each configuration are negligible., Ccoding efficiency gains for Class F under Low delay B main and Low delay B HE10 are 0.1% and 0.1%, respectively.

Discussed in track B but seems to rather relate to HL syntax / LTRP.

Solution Change 1: Mark MV as unavailable whenever the refidx refers a LTRP

Solution Change 2: Mark as unavailable if POC difference larger than a threshold, otherwise use it as usual (including scaling).

Q: How large is the threshold (currently 8/16 depending on frame structure). Would it be possible to make it switchable by encoder?

Some concern is raised about solution 2, as it modifies the AMVP process and has implication on hardware complexity. Solution 1 may be OK.

What is purpose? Coding efficiency? How large is the benefit? May be better to leave it as it is, i.e. use LTRP MV without scaling.

Proposals J0071, J0121, J0122 and J0302 are related to each other (but none of them are quite the same as each other).

JCTVC-J0341 Cross check of JCTVC-J0302 on Restricted usage of motion vectors for long-term reference picture in motion vector prediction process [Y. Takahashi, O. Nakagami, T. Suzuki (Sony)] [late]