Error mitigation for sublayers in video coding

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

receiving a bitstream comprising a video parameter set (VPS), one or more sublayers, and a buffering period (BP) maximum sublayers minus one (bp_max_sublayers_minus1) set to a value in a range of zero to a maximum number of sublayers specified by the VPS, and a hypothetical reference decoder (HRD) coded picture buffer count minus one (hrd_cpb_cnt_minus1) wherein the hrd_cpb_cnt_minus1 plus one specifies a number of alternative coded picture buffer (CPB) delivery schedules, and wherein a value of hrd_cpb_cnt_minus1 is constrained to a range from zero to thirty one, inclusive; and

decoding a picture from the one or more sublayers.

2. The method of claim 1 , wherein the bp_max_sublayers_minus1 is included in a buffering period supplemental enhancement information (SEI) message, and wherein the BP SEI message includes parameters associated with a maximum number of temporal sublayers specified by bp_max_sublayers_minus1.

3. The method of claim 2 , wherein the parameters in the BP SEI message include an initial coded picture buffer (CPB) removal delay and an initial CPB removal offset.

4. The method of claim 1 , wherein the maximum number of sublayers specified by the VPS is included in a VPS maximum sublayers minus one (vps_max_sublayers_minus1) plus one.

5. The method of claim 4 , wherein the vps_max_sublayers_minus1 is contained in the VPS.

6. The method of claim 2 , wherein the BP SEI message is for initialization of a HRD at a position of an associated access unit (AU) in decoding order.

7. The method of claim 1 , wherein the bitstream is a temporal scalable bitstream, wherein the one or more sublayers are temporal scalable layers of the bitstream, and wherein each sublayer includes video coding layer (VCL) network abstraction layer (NAL) units and associated non-VCL NAL units with a same value of a temporal identifier (TemporalId) variable.

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

encoding a bitstream comprising a video parameter set (VPS) and one or more sublayers;

encoding into the bitstream a buffering period (BP) supplemental enhancement information (SEI) message comprising a BP maximum sublayers minus one (bp_max_sublayers_minus1) set to a value in a range of zero to a maximum number of sublayers specified by the VPS, and a hypothetical reference decoder (HRD) coded picture buffer count minus one (hrd_cpb_cnt_minus1), wherein the hrd_cpb_cnt_minus1 plus one specifies a number of alternative coded picture buffer (CPB) delivery schedules, and wherein a value of hrd_cpb_cnt_minus1 is constrained to a range from zero to thirty one, inclusive;

initializing a HRD based on the BP SEI message; and

performing with the HRD a set of bitstream conformance tests on the sublayers.

9. The method of claim 8 , wherein the BP SEI message includes parameters associated with a maximum number of temporal sublayers specified by bp_max_sublayers_minus1.

10. The method of claim 9 , wherein the parameters in the BP SEI message include an initial coded picture buffer (CPB) removal delay and an initial CPB removal offset.

11. The method of claim 8 , wherein the maximum number of sublayers specified by the VPS is included in a VPS maximum sublayers minus one (vps_max_sublayers_minus1) plus one.

12. The method of claim 11 , wherein the vps_max_sublayers_minus1 is contained in the VPS.

13. The method of claim 8 , wherein the HRD is initialized at a position of an associated access unit (AU) in decoding order based on the BP SEI message.

14. The method of claim 8 , wherein the bitstream is a temporal scalable bitstream, wherein the one or more sublayers are temporal scalable layers of the bitstream, and wherein each sublayer includes video coding layer (VCL) network abstraction layer (NAL) units and associated non-VCL NAL units with a same value of a temporal identifier (TemporalId) variable.

15. A video coding device comprising:

a receiver configured to receive a bitstream comprising a video parameter set (VPS), one or more sublayers, a buffering period (BP) maximum sublayers minus one (bp_max_sublayers_minus1) set to a value in a range of zero to a maximum number of sublayers specified by the VPS, and a hypothetical reference decoder (HRD) coded picture buffer count minus one (hrd_cpb_cnt_minus1), wherein the hrd_cpb_cnt_minus1 plus one specifies a number of alternative coded picture buffer (CPB) delivery schedules, and wherein a value of hrd_cpb_cnt_minus1 is constrained to a range from zero to thirty one, inclusive; and

a processor coupled to the receiver and configured to decode a picture from the one or more sublayers.

16. The video coding device of claim 15 , wherein the bp_max_sublayers_minus1 is included in a buffering period supplemental enhancement information (SEI) message, and wherein the BP SEI message includes parameters associated with a maximum number of temporal sublayers specified by bp_max_sublayers_minus1.

17. The video coding device of claim 16 , wherein the parameters in the BP SEI message include an initial coded picture buffer (CPB) removal delay and an initial CPB removal offset.

18. The video coding device of claim 15 , wherein the maximum number of sublayers specified by the VPS is included in a VPS maximum sublayers minus one (vps_max_sublayers_minus1) plus one.

19. The video coding device of claim 18 , wherein the vps_max_sublayers_minus1 is contained in the VPS.

20. The video coding device of claim 16 , wherein the BP SEI message is for initialization of a HRD at a position of an associated access unit (AU) in decoding order.