Reference picture management in layered video coding

1. A method implemented by a decoder, the method comprising:

receiving a bitstream comprising a current picture and a reference picture list structure comprising an inter-layer reference picture flag, wherein the reference picture list structure is denoted as ref_pic_list_struct(listIdx, rplsIdx) where listIdx identifies a reference picture list, rplsIdx identifies an entry in the reference picture list, and ref_pic_list_struct is a syntax structure;

determining an entry in the reference picture list structure associated with the current picture is an inter-layer reference picture (ILRP) entry based on the inter-layer reference picture flag; and

decoding the current picture based on an inter-layer reference picture indicated by the entry in the reference picture list structure when the entry is the ILRP entry.

2. The method of claim 1 , wherein the reference picture list structure further comprises an ILRP layer indicator, and wherein the method further comprises determining a layer of the inter-layer reference picture based on the ILRP layer indicator when the entry is the ILRP entry.

3. The method of claim 1 , wherein the inter-layer reference picture flag is denoted as inter_layer_ref_pic_flag[listIdx][rplsIdx][i], wherein the inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to one when an i-th entry in the ref_pic_list_struct(listIdx, rplsIdx) is the ILRP entry, and wherein the inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to zero when the i-th entry in the ref_pic_list_struct(listIdx, rplsIdx) is not the ILRP entry.

4. The method of claim 3 , wherein the ref_pic_list_struct(listIdx, rplsIdx) and the inter_layer_ref_pic_flag[listIdx][rplsIdx][i] are contained in the bitstream in a sequence parameter set (SPS).

5. The method of claim 1 , further comprising decoding, by the decoder, the current picture according to intra-layer prediction based on an intra-layer reference picture indicated by the entry in the reference picture list structure when the entry is not the ILRP entry.

6. The method of claim 1 , wherein the inter-layer reference picture is in a same access unit (AU) as the current picture, and wherein the inter-layer reference picture is associated with a lower layer identifier than the current picture.

7. A method implemented by an encoder, the method comprising:

encoding a current picture into a bitstream, the current picture encoded according to inter-layer prediction based on an inter-layer reference picture;

encoding a reference picture list structure into the bitstream, the reference picture list structure comprising a plurality of entries for a plurality of reference pictures including an entry associated with the current picture and indicating the inter-layer reference picture, wherein the reference picture list structure is denoted as ref_pic_list_struct(listIdx, rplsIdx) where listIdx identifies a reference picture list, rplsIdx identifies an entry in the reference picture list, and ref_pic_list_struct is a syntax structure;

encoding an inter-layer reference picture flag into the bitstream, the inter-layer reference picture flag indicating that the entry associated with the current picture is an inter-layer reference picture (ILRP) entry; and

storing the bitstream for communication toward a decoder.

8. The method of claim 7 , further comprising encoding, by the encoder, an ILRP layer indicator into the bitstream, the ILRP layer indicator indicating a layer of the inter-layer reference picture.

9. The method of claim 7 , wherein the inter-layer reference picture flag is denoted as inter_layer_ref_pic_flag[listIdx][rplsIdx][i], wherein the inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to one when an i-th entry in the ref_pic_list_struct(listIdx, rplsIdx) is the ILRP entry, and wherein the inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to zero when the i-th entry in the ref_pic_list_struct(listIdx, rplsIdx) is not the ILRP entry.

10. The method of claim 9 , wherein the ref_pic_list_struct(listIdx, rplsIdx) and the inter_layer_ref_pic_flag[listIdx][rplsIdx][i] are encoded into the bitstream in a sequence parameter set (SPS).

11. The method of claim 9 , wherein the ref_pic_list_struct(listIdx, rplsIdx) and the inter_layer_ref_pic_flag[listIdx][rplsIdx][i] are encoded into a header associated with the current picture.

12. The method of claim 7 , wherein the inter-layer reference picture is in a same access unit (AU) as the current picture, and wherein the inter-layer reference picture is associated with a lower layer identifier than the current picture.

13. A decoder comprising:

a receiver configured to receive a bitstream comprising a current picture and a reference picture list structure comprising an inter-layer reference picture flag, wherein the reference picture list structure is denoted as ref_pic_list_struct(listIdx, rplsIdx) where listIdx identifies a reference picture list, rplsIdx identifies an entry in the reference picture list, and ref_pic_list_struct is a syntax structure; and

a processor configured to:

determine an entry in the reference picture list structure associated with the current picture is an inter-layer reference picture (ILRP) entry based on the inter-layer reference picture flag; and

decode the current picture based on an inter-layer reference picture indicated by the entry in the reference picture list structure when the entry is the ILRP entry.

14. The decoder of claim 13 , wherein the reference picture list structure further comprises an ILRP layer indicator, and wherein the processor is further configured to determine a layer of the inter-layer reference picture based on the ILRP layer indicator when the entry is the ILRP entry.

15. The decoder of claim 13 , wherein the inter-layer reference picture flag is denoted as inter_layer_ref_pic_flag[listIdx][rplsIdx][i], wherein the inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to one when an i-th entry in the ref_pic_list_struct(listIdx, rplsIdx) is the ILRP entry, and wherein the inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to zero when the i-th entry in the ref_pic_list_struct(listIdx, rplsIdx) is not the ILRP entry.

16. The decoder of claim 15 , wherein the ref_pic_list_struct(listIdx, rplsIdx) and the inter_layer_ref_pic_flag[listIdx][rplsIdx][i] are contained in the bitstream in a sequence parameter set (SPS).

17. The decoder of claim 13 , wherein the inter-layer reference picture is in a same access unit (AU) as the current picture, and wherein the inter-layer reference picture is associated with a lower layer identifier than the current picture.