Uncorrect pruning in derivation of spatial merging candidate

[antoine.robert]

In 8.5.2.3 Derivation process for spatial merging candidates, the pruning is:

• candidate B1 is pruned with A1
• candidate B0 is pruned with B1, A1
• candidate A0 is pruned with A1, B1, B0
• candidate B2 is pruned with A1, B1, B0, A0

But JVET-L0093 reduces it to:

• candidate B1 is pruned with A1
• candidate B0 is pruned with B1, A1
• candidate A0 is pruned with A1, B1, B0
• candidate B2 is pruned with A1, B1, B0, A0

The corresponding lines of the spec should be removed as, for example with candidate A0:

– The variables availableFlagA0, refIdxLXA0, predFlagLXA0 and mvLXA0 are derived as follows:

– If one or more of the following conditions are true, availableFlagA0 is set equal to 0, both components of mvLXA0 are set equal to 0, refIdxLXA0 is set equal to −1 and predFlagLXA0 is set equal to 0, with X being 0 or 1, and bcwIdxA0 is set equal to 0:

– availableA0 is equal to FALSE.
– availableA1 is equal to TRUE and the luma locations (xNbA1, yNbA1) and (xNbA0, yNbA0) have the same motion vectors and the same reference indices.
– availableB1 is equal to TRUE, the luma locations (xNbB1, yNbB1) and (xNbA0, yNbA0) have the same motion vectors and the same reference indices and MergeTriangleFlag[xCb][yCb] is equal to 1.
– availableB0 is equal to TRUE, the luma locations (xNbB0, yNbB0) and (xNbA0, yNbA0) have the same motion vectors and the same reference indices and MergeTriangleFlag[xCb][yCb] is equal to 1.

[LiZhang]

same as ticket #344. It seems the fixes haven't been integrated to VVC D6 vE.

[bbross]

Closed as duplicate of #344.