The changes introduced to support SCC in the transform unit syntax table have modified the condition for chroma QP offset coding compared to Rext.

In Rext the condition for coding cu_chroma_qp_offset_flag and cu_chroma_qp_offset_idx include the cbfChroma and !cu_transquant_bypass_flag values. In SCC the coding of these syntax elements was moved to chroma_qp_offset() to share with palette coding. However, since the aforementioned variables are no longer present in chroma_qp_offset() these conditions should be added in transform unit before calling chroma_qp_offset().

The current wording in JCTVC-W1005-v3.doc is that chroma QP offset gets coded inside transform unit even when cbfChroma is 0 or cu_transquant_bypass_flag is 1. This mismatches with the HM model and Rext behavior.

Rext transform unit syntax:

if( cu_chroma_qp_offset_enabled_flag  &&  cbfChroma  &&
    !cu_transquant_bypass_flag  &&  !IsCuChromaQpOffsetCoded ) {
    cu_chroma_qp_offset_flag
    if( cu_chroma_qp_offset_flag  &&  chroma_qp_offset_list_len_minus1 > 0 )
        cu_chroma_qp_offset_idx
}

SCC transform unit syntax table:

if( cbfLuma  | |  cbfChroma ) {
    <removed for brevity>
    delta_qp( )
    chroma_qp_offset( )

SCC chroma QP offset syntax:

chroma_qp_offset( ) {
    if( cu_chroma_qp_offset_enabled_flag  &&  !IsCuChromaQpOffsetCoded ) {
        cu_chroma_qp_offset_flag
        if( cu_chroma_qp_offset_flag  &&  chroma_qp_offset_list_len_minus1 > 0 )
            cu_chroma_qp_offset_idx
    }
}