This bug occures when EnableTMVPFlag = 1, ColDir = 1 and NumRexIdx(REF_PIC_LIST_0) > 1

Reference decoder parses Slice header of first slice in the picture twice (except the very first slice). First - when variable m_bFirstSliceInPicture is false and second - when this variable is true. When m_bFirstSliceInPicture is false decoder initializes current slice data by data of previous slice (just in case the current slice is dependent one I believe), when m_bFirstSliceInPicture is true – by default values.

Let’s consider what will happen if current slice is the first slice of P picture following after B picture in decoding order. Last slice of B picture had ColDir = 1. Default values for ColDir is 0. In code below the "collocated_ref_idx" will be read if ColDir == 0 (right case for P_SLICE, second pass of slice header parsing) and won’t be read if ColDir == 1 (first pass of slice header parsing). So when decoder is trying to parse Slice header for the first time with wrong value of ColDir it skips reading of "collocated_ref_idx" , brokes CABAC decoding and stops on some asserts (see example in attachment)

if ( rpcSlice->getEnableTMVPFlag() )
{

if ( rpcSlice->getSliceType() == B_SLICE )
{

READ_FLAG( uiCode, "collocated_from_l0_flag" );
rpcSlice->setColDir(uiCode);

}

if ( rpcSlice->getSliceType() != I_SLICE &&

((rpcSlice->getColDir()==0 && rpcSlice->getNumRefIdx(REF_PIC_LIST_0)>1)

(rpcSlice->getColDir() ==1 && rpcSlice->getNumRefIdx(REF_PIC_LIST_1)>1)))

{

READ_UVLC( uiCode, "collocated_ref_idx" );
rpcSlice->setColRefIdx(uiCode);

}

}

The bug could be easily fixed for example by initializing of ColDir to 0 (rpcSlice->setColDir(0);) before line “if ( rpcSlice->getSliceType() == B_SLICE )”