id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
42	CTU bits/distortion calculation mistake for I slice when QTBT is enabled	FangliangSong		"Because of separated luma CTB and chroma CTB for I Slice, TEncCu::xCompressCU is invoked twice in TEncCu::compressCtu, the first time for the luma CTB encoding and the second time for the chroma CTB encoding. On the second invocation, four bits/distortion related values of CTU in pCtu (function parameter of TEncCu::compressCtu): m_dTotalCost, m_uiTotalDistortion, m_uiTotalBits, and m_uiNumPartition, are overwritten. It leads to the four values of a CTU are that of chroma CTB in the CTU, and that of luma CTB in the CTU are excluded since JEM-3.0. The mistake has two influences:
1. R-D related values of I slice are that of chroma components, and the slice level delta QP RDO process does wrong QP selection when DeltaQpRD is on.
2. The remaining bit number of current I frame is updated incorrectly when CTU level rate control is on. More specially, the remaining bit number of current I frame is only subtracted by chroma CTB bits.
The original code of encoding chroma CTB is as below:
#if JVET_C0024_QTBT
if (pCtu->getSlice()->isIntra())
{
   …
   xCompressCU(/*long arguments*/);
}
#endif
A simple solution to this bug is as below:
#if JVET_C0024_QTBT
if (pCtu->getSlice()->isIntra())
{
   …
   Double dLumaTotalCost = pCtu->getTotalCost();
   Distortion dLumaTotalDistortion = pCtu->getTotalDistortion();
   UInt uiLumaTotalBits = pCtu->getTotalBits();
   UInt uiLumaTotalBins = pCtu->getTotalBins();
   xCompressCU(/*long arguments*/);
   pCtu->getTotalCost() += dLumaTotalCost;
   pCtu->getTotalDistortion() += dLumaTotalDistortion;
   pCtu->getTotalBits() += uiLumaTotalBits;
   pCtu->getTotalBins() += uiLumaTotalBins;
}
#endif
The bug still exit in latest software version (JEM-4.1), and has no impact under CTC.
"	defect	closed	minor	HM-16.6-JEM-4.2	JEM	HM-16.6-JEM-4.0	fixed	CTU, bits, distortion, I slice, QTBT	ksuehring XiangLi jvet@…