Messages from Minhua:

In the TMuC TComDataCU.cpp, fillMvpCand() ----- the mvp list is reordered if the partition is 2NxN or Nx2N.

Line 3915-

else if ( ( ((eCUMode == SIZE_2NxN)

(eCUMode == SIZE_2NxnU)

(eCUMode == SIZE_2NxnD)) && uiPartIdx == 0 && m_pcSlice->isEqualRef(eRefPicList, m_cMvFieldB.getRefIdx(), iRefIdx) )

&& iAboveMvIdx > 0 )

{

cTempMv = pInfo->m_acMvCand[0];
pInfo->m_acMvCand[0] = pInfo->m_acMvCand[iAboveMvIdx];
pInfo->m_acMvCand[iAboveMvIdx] = cTempMv;

}

else if ( ( ((eCUMode == SIZE_Nx2N)

(eCUMode == SIZE_nLx2N)

(eCUMode == SIZE_nRx2N)) && uiPartIdx == 1 && m_pcSlice->isEqualRef(eRefPicList, m_cMvFieldC.getRefIdx(), iRefIdx))

&& iCornerMvIdx > 0 )

{

cTempMv = pInfo->m_acMvCand[0];
pInfo->m_acMvCand[0] = pInfo->m_acMvCand[iCornerMvIdx];
pInfo->m_acMvCand[iCornerMvIdx] = cTempMv;

}

The condition (I marked bold) seems incorrect. m_cMvFieldB and m_cMvFieldC aren't initialized in the decoding process, so these conditions are never fulfilled.

And my suggestion:

The goal of these 'boldface' checks is to check the equality of two reference indices, but as Minhua indicated, they does not work due to the non-initialization. Furthermore, the next conditions iAboveMvIdx > 0 and iCornerMvIdx > 0 already do the same thing.

Thus instead of initializing them correctly, simply removal of the bold parts is sufficient to get the original motivation to use the AVC-style motion predictor as the 1st place in AMVP queue for rectangular partition modes.