DPB size based reference picture entry constraints

A method implemented by an encoder, the method comprising:

• encoding a current picture based on a reference picture into a bitstream;
• encoding a decoded picture buffer parameter syntax structure (dpb_parameters( )) into the bitstream;
• encoding a reference picture list syntax structure (ref_pic_list_struct( )) into the bitstream, wherein the reference picture list syntax structure indicates the reference picture and comprises a number of reference entries (num_ref_entries), and wherein the number of reference entries are constrained to a range of zero to a maximum decoded picture buffer size plus an offset, wherein the num_ref_entries specifies a number of entries in the ref_pic_list_struct( ), wherein the dpb_parameters( ) comprises a maximum decoded picture buffer minus one (max_dec_pic_buffering_minus1) that corresponds to the maximum decoded picture buffer size, wherein when the dpb_parameters( ) is included in a video parameter set (VPS), output layer sets (OLSs) to which the dpb_parameters( ) applies are specified by the VPS, and wherein when the dpb_parameters( ) is included in a sequence parameter set (SPS), OLSs to which the dpb_parameters( ) applies are specified by the SPS;
• and
• storing the bitstream for communication toward a decoder.

A video coding device comprising:

• a memory storing instructions;
• one or more processors coupled to the memory, the one or more processors configured to execute the instructions to cause the video decoding device to:
• receive a bitstream comprising a current picture, a decoded picture buffer parameter syntax structure (dpb_parameters( )), and a reference picture list syntax structure (ref_pic_list_struct( )) comprising a number of reference entries (num_ref_entries) constrained to a range of zero to a maximum decoded picture buffer size plus an offset, wherein the num_ref_entries specifies a number of entries in the ref_pic_list_struct( ), wherein the dpb_parameters( ) comprises a maximum decoded picture buffer minus one (max_dec_pic_buffering_minus1) that corresponds to the maximum decoded picture buffer size, wherein when the dpb_parameters( ) is included in a video parameter set (VPS), output layer sets (OLSs) to which the dpb_parameters( ) applies are specified by the VPS, and wherein when the dpb_parameters( ) is included in a sequence parameter set (SPS), OLSs to which the dpb_parameters( ) applies are specified by the SPS;
• and
• decode the current picture based on the ref_pic_list_struct( ) and dpb_parameters( ) to produce a decoded picture.