This redundat computation only happens when the following tools are both turned on:

1. One-pass ALF (ALFEncodePassReduction: 1 or 2)
2. Multi-slice picture (SliceMode : 1 or 2)

Not affect common test condition and not affect one-slice picture case.

Problem statement

In TEncAdaptiveLoopFilter.cpp,

Void TEncAdaptiveLoopFilter::xEncodeCUAlfCtrlFlags()
{
#if MTK_NONCROSS_INLOOP_FILTER

if(m_uiNumSlicesInPic > 1)
{

for(UInt s=0; s< m_uiNumSlicesInPic; s++)
{

for(UInt idx=0; idx< m_pSlice[s].getNumLCUs(); idx++)
{

CAlfLCU& cAlfLCU = m_pSlice[s][idx];

for(UInt i=0; i< cAlfLCU.getNumCtrlFlags(); i++)
{

m_pcEntropyCoder->encodeAlfCtrlFlag(cAlfLCU.getCUCtrlFlag(i));

}

}

}

}

#endif

for( UInt uiCUAddr = 0; uiCUAddr < m_pcPic->getNumCUsInFrame() ; uiCUAddr++ )
{

TComDataCU* pcCU = m_pcPic->getCU( uiCUAddr );
xEncodeCUAlfCtrlFlag(pcCU, 0, 0);

}

}

This function, xEncodeCUAlfCtrlFlags, is only used for 1-pass ALF to calculate the bitrate of ALF CU-on/off flags. When uiNumSlicesInPic > 1, there are redundant bitrate calculation.

Fix

Add one "return" for multi-slice picture case, the modification is as follows,

Void TEncAdaptiveLoopFilter::xEncodeCUAlfCtrlFlags()
{
#if MTK_NONCROSS_INLOOP_FILTER

if(m_uiNumSlicesInPic > 1)
{

for(UInt s=0; s< m_uiNumSlicesInPic; s++)
{

for(UInt idx=0; idx< m_pSlice[s].getNumLCUs(); idx++)
{

CAlfLCU& cAlfLCU = m_pSlice[s][idx];

for(UInt i=0; i< cAlfLCU.getNumCtrlFlags(); i++)
{

m_pcEntropyCoder->encodeAlfCtrlFlag(cAlfLCU.getCUCtrlFlag(i));

}

}

}
return;

}

#endif

for( UInt uiCUAddr = 0; uiCUAddr < m_pcPic->getNumCUsInFrame() ; uiCUAddr++ )
{

TComDataCU* pcCU = m_pcPic->getCU( uiCUAddr );
xEncodeCUAlfCtrlFlag(pcCU, 0, 0);

}

}