A method of decoding a coded video bitstream implemented by a video decoder. The method includes determining a split mode for a coding tree unit (CTU) in an encoded bitstream, where the split mode is one of triple tree (TT), vertical binary tree (BT), and horizontal BT; marking a coding unit (CU) from the CTU as not to be predicted by intra prediction when one of three conditions is met; parsing the encoded bitstream to obtain a prediction unit and residual information for the CU from the CTU; and reconstructing the CU based on the prediction unit and the residual information when the CU has been marked.