Reference picture management in video coding

An encoding device, comprising:

• a memory storing instructions;
• and
• one or more processors coupled to the memory, the one or more processors configured to execute the instructions stored in the memory to cause the encoding device to:
• encode a reference picture list structure for a current slice into a coded video bitstream, wherein the reference picture list structure contains a number of entries;
• determine a default number of active entries in a reference picture list for the current slice;
• determine the reference picture list for the current slice, wherein the reference picture list contains a number of active entries and a number of inactive entries;
• set the number of active entries in the reference picture list equal to the number of entries in the reference picture list structure when the default number of active entries in the reference picture list is greater than the number of entries in the reference picture list structure;
• encode an override flag into the coded video bitstream, wherein the number of active entries in the reference picture list is set equal to the number of entries in the reference picture list structure when a value of the override flag is false;
• encode a second syntax element into a slice header of the current slice when the value of the override flag is true, and
• wherein an order of entries in the reference picture list structure is the same as an order of corresponding reference pictures in the reference picture list,
• wherein at least one active entry of the reference picture list is used for inter prediction of at least one reconstructed block, and wherein the inactive entries are not used for inter prediction of a current picture, and
• wherein the reference picture list structure, ref_pic_list_struct (listIdx, rplsIdx), includes two separate indexes, listIdx and rplsIdx,
• wherein the default number of active entries in the reference picture list is determined based on a first syntax element from a picture parameter set represented in the coded video bitstream, and
• wherein a value of the first syntax element plus 1 is the default number of active entries in the reference picture list, and wherein the second syntax element plus 1 is the number of active entries in the reference picture list.

A non-transitory computer program product comprising program code for performing a method when executed on a computer or one or more processors, the method comprising:

• encoding a reference picture list structure for a current slice into a coded video bitstream, wherein the reference picture list structure contains a number of entries;
• determining a default number of active entries in a reference picture list for the current slice;
• determining the reference picture list for the current slice, wherein the reference picture list contains a number of active entries and a number of inactive entries;
• setting the number of active entries in the reference picture list equal to the number of entries in the reference picture list structure when the default number of active entries in the reference picture list is greater than the number of entries in the reference picture list structure;
• encoding an override flag into the coded video bitstream, wherein the number of active entries in the reference picture list is set equal to the number of entries in the reference picture list structure when a value of the override flag is false;
• and
• obtaining a second syntax element from a slice header of the current slice when the value of the override flag is true,
• wherein an order of entries in the reference picture list structure is the same as an order of corresponding reference pictures in the reference picture list,
• wherein at least one active entry of the reference picture list is used for inter prediction of at least one reconstructed block, and wherein the inactive entries are not used for inter prediction of a current picture,
• wherein the reference picture list structure, ref_pic_list_struct (listIdx, rplsIdx), includes two separate indexes, listIdx and rplsIdx,
• wherein the default number of active entries in the reference picture list is determined based on a first syntax element from a picture parameter set represented in the coded video bitstream, and
• wherein a value of the first syntax element plus 1 is the default number of active entries in the reference picture list, and wherein the second syntax element plus 1 is the number of active entries in the reference picture list.