Opened 5 years ago
Last modified 4 years ago
#337 closed defect
Cross component prediction tool in VTM but not described in spec — at Version 1
Reported by: | jonathang | Owned by: | |
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Priority: | minor | Milestone: | |
Component: | VTM | Version: | VTM-5.0 |
Keywords: | Cc: | ksuehring, XiangLi, fbossen, jvet@… |
Description (last modified by ksuehring)
In VTM 5.0 within CABACReader::transform_unit, the following code may result in the decoding of a CCP flag, and then a CCP alpha value
if( TU::hasCrossCompPredInfo( tu, compID ) ) { cross_comp_pred( tu, compID ); } void CABACReader::cross_comp_pred( TransformUnit& tu, ComponentID compID ) { signed char alpha = 0; unsigned ctxBase = ( compID == COMPONENT_Cr ? 5 : 0 ); unsigned symbol = m_BinDecoder.decodeBin( Ctx::CrossCompPred(ctxBase) ); if( symbol ) { // Cross-component prediction alpha is non-zero. symbol = m_BinDecoder.decodeBin( Ctx::CrossCompPred(ctxBase+1) ); if( symbol ) { // alpha is 2 (symbol=1), 4(symbol=2) or 8(symbol=3). // Read up to two more bits symbol += unary_max_symbol( Ctx::CrossCompPred(ctxBase+2), Ctx::CrossCompPred(ctxBase+3), 2 ); } alpha = ( 1 << symbol ); if( m_BinDecoder.decodeBin( Ctx::CrossCompPred(ctxBase+4) ) ) { alpha = -alpha; } } tu.compAlpha[compID] = alpha; }
In the current spec there are no syntax elements for CCP. Given the CCLM intra prediction mode and the joint chroma residual coding, is CCP to be removed?
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