1. A method for decoding video data, the method comprising:', 'decoding a buffering period supplemental enhancement information (SEI) message associated with an access unit (AU);', 'decoding a duration between coded picture buffer (CPB) removal time of a first decoding unit (DU) in the AU and CPB removal time of a second DU from the buffering period SEI message, wherein the AU has a Temporalld equal to 0;', 'determining a removal time of the first DU based at least in part on the decoded duration; and', 'decoding video data of the first DU based at least in part on the removal time.

2. The method of claim 1 , wherein the second DU is subsequent to the first DU in decoding order and in the same AU as the first DU.

3. The method of claim 2, wherein the second DU is immediately subsequent to the first DU in the AU in decoding order or a last DU in the AU in decoding order.

4. The method of claim 1, further comprising:', 'decoding one or more sub-picture level CPB parameters, wherein determining the removal time of the first DU comprises determining the removal time of the first DU based at least in part on the decoded duration and the sub-picture level CPB parameters.

5. The method of claim 4, wherein decoding one or more sub-picture level CPB parameters comprises:', 'decoding a sub-picture timing supplemental enhancement information (SEI) message that is associated with the first DU.

6. The method of claim 5, wherein the second DU is a last DU in the AU in decoding order, and wherein decoding the sub-picture SEI message comprises:', 'decoding the duration between a removal time of the last DU and the removal time of the first DU in the sub-picture timing SEI message.

7. The method of claim 4, further comprising:', 'decoding a sequence level flag to determine presence of the sub-picture level CPB parameters either in picture timing SEI messages or in sub-picture timing SEI messages.

8. The method of claim 1, wherein the first DU comprises a non- video coding layer (VCL) network abstraction layer (NAL) unit with nal unit type equal to UNSPECO, EOS_NUT, EOB NUT, in the range of RSV NVCL44 to RSV_NVCL47 or in the range of UNSPEC48 to UNSPEC63.

9. The method of claim 1, further comprising:', 'deriving at least one of a CPB arrival time and a CPB nominal removal time for the AU at both an access unit level and a sub-picture level regardless of a value of a syntax element that defines whether the first DU is the AU

10. A video decoding device comprising a video decoder configured to:', 'decode a buffering period supplemental enhancement information (SEI) message associated with an access unit (AU);', 'decode a duration between coded picture buffer (CPB) removal time of a first decoding unit (DU) in the AU and CPB removal time of a second DU from the buffering period SEI message, wherein the AU has a Temporalld equal to 0;', 'determine a removal time of the first DU based at least in part on the decoded duration; and', 'decode video data of the first DU based at least in part on the removal time

11. The video decoding device of claim 10, wherein the second DU is subsequent to the first DU in decoding order and in the same AU as the first DU

12. The video decoding device of claim 11, wherein the second DU is immediately subsequent to the first DU in the AU in decoding order or a last DU in the AU in decoding order

13. The video decoding device of claim 10, the video decoder further configured to decode one or more sub-picture level CPB parameters, wherein determine the removal time of the first DU comprises determine the removal time of the first DU based at least in part on the decoded duration and the sub-picture level CPB parameters

14. The video decoding device of claim 13, wherein the video decoder is further configured to decode one or more sub-picture level CPB parameters by decoding a sub- picture timing supplemental enhancement information (SEI) message that is associated with the first DU

15. The video decoding device of claim 14, wherein the second DU is a last DU in the AU in decoding order, and wherein decode the sub-picture SEI message comprises decode the duration between a removal time of the last DU and the removal time of the first DU in the sub-picture timing SEI message

16. The video decoding device of claim 13, the video decoder further configured to decode a sequence level flag to determine presence of the sub-picture level CPB parameters either in picture timing SEI messages or in sub-picture timing SEI messages

17. The video decoding device of claim 10, wherein the first DU comprises a non- video coding layer (VCL) network abstraction layer (NAL) unit with nal unit type equal to UNSPECO, EOS_NUT, EOB NUT, in the range of RSV NVCL44 to', 'RSV_NVCL47 or in the range of UNSPEC48 to UNSPEC63

18. The video decoding device of claim 10, the video decoder further configured to derive at least one of a CPB arrival time and a CPB nominal removal time for the AU at both an access unit level and a sub-picture level regardless of a value of a syntax element that defines whether the first DU is the AU

19. A computer-readable storage medium having stored thereon instructions that, when executed, cause a processor of a device for decoding video data to:', 'decode a buffering period supplemental enhancement information (SEI) message associated with an access unit (AU);', 'decode a duration between coded picture buffer (CPB) removal time of a first decoding unit (DU) in the AU and CPB removal time of a second DU from the buffering period SEI message, wherein the AU has a Temporalld equal to 0;', 'determine a removal time of the first DU based at least in part on the decoded duration; and', 'decode video data of the first DU based at least in part on the removal time.

20. The computer-readable storage medium of claim 19, wherein the second DU is subsequent to the first DU in decoding order and in the same AU as the first DU.

21. The computer-readable storage medium of claim 19, wherein the second DU is immediately subsequent to the first DU in the AU in decoding order or a last DU in the AU in decoding order.

22. A video decoding device comprising:', 'means for decoding a buffering period supplemental enhancement information (SEI) message associated with an access unit (AU);', 'means for decoding a duration between coded picture buffer (CPB) removal time of a first decoding unit (DU) in the AU and CPB removal time of a second DU from the buffering period SEI message, wherein the AU has a Temporalld equal to 0;', 'means for determining a removal time of the first DU based at least in part on the decoded duration; and', 'means for decoding video data of the first DU based at least in part on the removal time.

23. The video decoding device of claim 22, wherein the second DU is subsequent to the first DU in decoding order and in the same AU as the first DU.

24. The video decoding device of claim 22, wherein the second DU is immediately subsequent to the first DU in the AU in decoding order or a last DU in the AU in decoding order.

25. A method for encoding video data, the method comprising:', 'determining a duration between coded picture buffer (CPB) removal time of a first decoding unit (DU) in an access unit (AU) and CPB removal time of a second DU in the AU, wherein the AU has a Temporalld equal to 0; and', 'encoding a buffering period supplemental enhancement information (SEI) message associated with an access unit (AU), wherein the duration is encoded within the buffering period SEI message.

26. The method of claim 25, wherein the second DU is subsequent to the first DU in decoding order and in the same AU as the first DU.

27. The method of claim 26, wherein the second DU is immediately subsequent to the first DU in the AU in decoding order or a last DU in the AU in decoding order.

28. The method of claim 25, further comprising:', 'encoding one or more sub-picture level CPB parameters, wherein determining the duration comprises determining the removal time of the first DU based at least in part on the sub-picture level CPB parameters.

29. The method of claim 28, wherein encoding one or more sub-picture level CPB parameters comprises:', 'encoding a sub-picture timing supplemental enhancement information (SEI) message that is associated with the first DU, wherein the sub-picture timing SEI message includes the one or more sub-picture level CPB parameters.

30. The method of claim 29, wherein the second DU is a last DU in the AU in decoding order, and wherein encoding the sub-picture SEI message comprises:', 'encoding the duration in the sub-picture timing SEI message.

31. The method of claim 28, further comprising:', 'encoding a sequence level flag to indicate presence of the sub-picture level CPB parameters either in picture timing SEI messages or in sub-picture timing SEI messages.

32. The method of claim 25, wherein the first DU comprises a non-video coding layer (VCL) network abstraction layer (NAL) unit with nal unit type equal to', 'UNSPECO, EOS NUT, EOB NUT, in the range of RSV NVCL44 to RSV NVCL47 or in the range of UNSPEC48 to UNSPEC63.

33. The method of claim 25, further comprising:', 'deriving at least one of a CPB arrival time and a CPB nominal removal time for the AU at both an access unit level and a sub-picture level regardless of a value of a syntax element that defines whether the first DU is the AU.

34. A video encoding device comprising a video encoder configured to:', 'determine a duration between coded picture buffer (CPB) removal time of a first decoding unit (DU) in an access unit (AU) and CPB removal time of a second DU in the AU, wherein the AU has a Temporalld equal to 0; and', 'encode a buffering period supplemental enhancement information (SEI) message associated with an access unit (AU), wherein the duration is encoded within the buffering period SEI message.

35. The video encoding device of claim 34, wherein the second DU is subsequent to the first DU in decoding order and in the same AU as the first DU.

36. The video encoding device of claim 35, wherein the second DU is immediately subsequent to the first DU in the AU in decoding order or a last DU in the AU in decoding order.

37. The video encoding device of claim 34, wherein the video encoder is further configured to encode one or more sub-picture level CPB parameters, wherein determining the duration comprises determining the removal time of the first DU based at least in part on the sub-picture level CPB parameters.

38. The video encoding device of claim 37, wherein the video encoder is further configured to encode one or more sub-picture level CPB parameters by encoding a sub- picture timing supplemental enhancement information (SEI) message that is associated with the first DU.

39. The video encoding device of claim 38, wherein the second DU is a last DU in the AU in decoding order, and wherein encode the sub-picture SEI message comprises encode the duration in the sub-picture timing SEI message.

40. The video encoding device of claim 37, wherein the video encoder is further configured to encode a sequence level flag to indicate presence of the sub-picture level CPB parameters either in picture timing SEI messages or in sub-picture timing SEI messages.

41. The video encoding device of claim 34, wherein the first DU comprises a non- video coding layer (VCL) network abstraction layer (NAL) unit with nal unit type equal to UNSPECO, EOS_NUT, EOB NUT, in the range of RSV NVCL44 to', 'PvSV_NVCL47 or in the range of UNSPEC48 to UNSPEC63.

42. The video encoding device of claim 34, wherein the video encoder is further configured to derive at least one of a CPB arrival time and a CPB nominal removal time for the AU at both an access unit level and a sub-picture level regardless of a value of a syntax element that defines whether the first DU is the AU.

43. A computer-readable storage medium having stored thereon instructions that, when executed, cause a processor of a device for decoding video data to:', 'determine a duration between coded picture buffer (CPB) removal time of a first decoding unit (DU) in an access unit (AU) and CPB removal time of a second DU in the AU, wherein the AU has a Temporalld equal to 0; and', 'encode a buffering period supplemental enhancement information (SEI) message associated with an access unit (AU), wherein the duration is encoded within the buffering period SEI message.

44. The computer-readable storage medium of claim 43, wherein the second DU is subsequent to the first DU in decoding order and in the same AU as the first DU.

45. The computer-readable storage medium of claim 43, wherein the second DU is immediately subsequent to the first DU in the AU in decoding order or a last DU in the AU in decoding order.']