Text/SW mismatch in TMVP scaling with ILRPs (8.5.2.12)

[fbossen]

There is a condition such as:

– If RefPicList[ X ][ refIdxLX ] is an LTRP, or colPocDiff is equal to currPocDiff, mvLXCol is derived as follows:
mvLXCol = Clip3( −131072, 131071, mvCol ) (598)

As far as I can tell, to match the behaviour of the software, this should be

– If RefPicList[ X ][ refIdxLX ] is marked as "used for long-term reference", or colPocDiff is equal to currPocDiff, mvLXCol is derived as follows:
mvLXCol = Clip3( −131072, 131071, mvCol ) (598)

[yk]

Frank, is replacing "an LTRP" with "marked as "used for long-term reference"" the only change suggested herein? If that's the case, then they are equivalent, as LTRP is defined as a picture that is marked as "used for long-term reference".

[fbossen]

Ye-Kui: yes, that is the only change. However my understanding is that LTRP and marked as "used for long-term reference" are two different things:
LTRP means LTRP
marked as "used for long-term reference" means LTRP or ILRP

For reference, definitions of LTRP and ILRP are as follows:
3.85 long-term reference picture (LTRP): A picture with nuh_layer_id equal to the nuh_layer_id of the current picture and marked as "used for long-term reference".
3.66 inter-layer reference picture (ILRP): A picture in the same AU with the current picture, with nuh_layer_id less than the nuh_layer_id of the current picture, and is marked as "used for long-term reference".

[yk]

I see, Frank, you are right. Indeed, the intention (I think) was to cover both (usual) LTRPs and ILRPs, thus your suggested change is good.

Then what about the following condition that appeared twice in clause 8.5.2.7 (Derivation process for merge motion vector difference)?

– If RefPicList[ 0 ][ refIdxL0 ] is not an LTRP and RefPicList[ 1 ][ refIdxL1 ] is not an LTRP, the following applies:

I guess we should make the same change herein?

[jlchen]

Ye-kui, the issue you mentioned was reported in #1171 by Frank.

Seems we agreed on the reported issue and the solution. Will be fixed in JVET-S2001-vC.