Methods for coding or decoding video parameter set or sequence parameter set

1. An apparatus, comprising:

a memory configured to store instructions; and

one or more processors configured to execute the instructions to cause the apparatus to:

determine whether a coded video sequence (CVS) contains equal number of profile, tier and level (PTL) syntax structures and output layer sets (OLSs); and

in response to the CVS containing equal number of PTL syntax structures and OLSs, code a bitstream without signaling a first PTL syntax element specifying an index, to a list of PTL syntax structures in a video parameter set (VPS), of a PTL syntax structure that applies to a corresponding OLS in the VPS.

2. The apparatus of claim 1 , wherein the one or more processors are configured to execute the instructions to cause the apparatus to:

determine whether the number of PTL syntax structures being equal to one; and

in response to the number of PTL syntax structures being equal to one, code the bitstream without signaling the first PTL syntax element in the VPS.

3. The apparatus of claim 1 , wherein the one or more processors are configured to execute the instructions to cause the apparatus to:

in response to the number of PTL syntax structures being greater than one and different from the number of the OLSs, signal, in the VPS, the first PTL syntax element with a fixed length.

4. The apparatus of claim 1 , wherein the one or more processors are configured to execute the instructions to cause the apparatus to:

determine whether at least one of a PTL syntax structure, a decoded picture buffer (DPB) parameters syntax structure, or a hypothetical reference decoder (HRD) parameters syntax structure is present in a Sequence Parameter Set (SPS) of the bitstream;

determine whether a first value is greater than one, the first value specifying a maximum number of temporal sublayers present in a coded layer video sequence (CLVS) referring to the SPS; and

when at least one of the PTL syntax structure, the DPB parameters syntax structure, or the HRD parameters syntax structure is present in the SPS and the first value is greater than one, signal a flag configured to control a presence of syntax elements in the DPB parameters syntax structure in the SPS.

5. The apparatus of claim 4 , wherein the one or more processors are configured to execute the instructions to cause the apparatus to:

when the first value is equal to or smaller than one, signaling one or more syntax elements in the DPB parameters syntax structure, without signaling the flag in the SPS.

6. The apparatus of claim 1 , wherein the one or more processors are configured to execute the instructions to cause the apparatus to:

determine a value of a first Sequence Parameter Set (SPS) syntax element, the first SPS syntax element specifying an identifier of the VPS referred to by a SPS when the value of the first SPS syntax element is greater than zero;

in response to the value of the first SPS syntax element is greater than zero, assign a range of a second SPS syntax element specifying a maximum number of temporal sublayers present in each coded layer video sequence (CLVS) referring to the SPS based on a corresponding VPS syntax element; and

in response to the value of the first SPS syntax element equal to zero, assign the range of the second SPS syntax element specifying the maximum number of temporal sublayers present in each CLVS referring to the SPS to be an inclusive range of zero to a fixed value.

7. A non-transitory computer-readable storage medium storing a set of instructions that are executable by one or more processors of a device to cause the device to perform a method for encoding video, comprising:

determining whether a coded video sequence (CVS) contains equal number of profile, tier and level (PTL) syntax structures and output layer sets (OLSs); and

in response to the CVS containing equal number of PTL syntax structures and OLSs, coding a bitstream without signaling a first PTL syntax element specifying an index, to a list of PTL syntax structures in a video parameter set (VPS), of a PTL syntax structure that applies to a corresponding OLS in the VPS.

8. The non-transitory computer-readable storage medium of claim 7 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

determining whether the number of PTL syntax structures being equal to one; and

in response to the number of PTL syntax structures being equal to one, coding the bitstream without signaling the first PTL syntax element in the VPS.

9. The non-transitory computer-readable storage medium of claim 7 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

in response to the number of PTL syntax structures being greater than one and different from the number of the OLSs, signaling, in the VPS, the first PTL syntax element with a fixed length.

10. The non-transitory computer-readable storage medium of claim 7 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

determining whether at least one of a PTL syntax structure, a decoded picture buffer (DPB) parameters syntax structure, or a hypothetical reference decoder (HRD) parameters syntax structure is present in a Sequence Parameter Set (SPS) of the bitstream;

determining whether a first value is greater than one, the first value specifying a maximum number of temporal sublayers present in a coded layer video sequence (CLVS) referring to the SPS; and

when at least one of the PTL syntax structure, the DPB parameters syntax structure, or the HRD parameters syntax structure is present in the SPS and the first value is greater than one, signaling a flag configured to control a presence of syntax elements in the DPB parameters syntax structure in the SPS.

11. The non-transitory computer-readable storage medium of claim 10 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

when the first value is equal to or smaller than one, signaling one or more syntax elements in the DPB parameters syntax structure, without signaling the flag in the SPS.

12. The non-transitory computer-readable storage medium of claim 7 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

determining a value of a first Sequence Parameter Set (SPS) syntax element, the first SPS syntax element specifying an identifier of the VPS referred to by a SPS when the value of the first SPS syntax element is greater than zero;

in response to the value of the first SPS syntax element is greater than zero, assigning a range of a second SPS syntax element specifying a maximum number of temporal sublayers present in each coded layer video sequence (CLVS) referring to the SPS based on a corresponding VPS syntax element; and

in response to the value of the first SPS syntax element equal to zero, assigning the range of the second SPS syntax element specifying the maximum number of temporal sublayers present in each CLVS referring to the SPS to be an inclusive range of zero to a fixed value.

13. A non-transitory computer-readable storage medium storing a set of instructions that are executable by one or more processors of a device to cause the device to perform a method for decoding video, comprising:

receiving a bitstream comprising a coded video sequence (CVS) and a video parameter set (VPS);

determining whether the CVS has equal number of profile, tier and level (PTL) syntax structures and output layer sets (OLSs); and

in response to the number of PTL syntax structures being equal to the number of the OLSs, skipping decoding a first PTL syntax element specifying an index, to a list of PTL syntax structures in the VPS, of a PTL syntax structure that applies to a corresponding OLS when decoding the VPS.

14. The non-transitory computer-readable storage medium of claim 13 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

in response to the number of PTL syntax structures being equal to the number of the OLSs, determining the first PTL syntax element to be equal to an index of the OLS to which the PTL syntax structure specified by the first PTL syntax element applies.

15. The non-transitory computer-readable storage medium of claim 13 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

determining whether the number of PTL syntax structures being equal to one; and

in response the number of PTL syntax structures being equal to one, skipping decoding the first PTL syntax element when decoding the VPS.

16. The non-transitory computer-readable storage medium of claim 15 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

in response to the number of PTL syntax structures being equal to one, determining the first PTL syntax element to be zero.

17. The non-transitory computer-readable storage medium of claim 13 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

in response to the number of PTL syntax structures being greater than one and different from the number of the OLSs, decoding the first PTL syntax element with a fixed length in the VPS.

18. The non-transitory computer-readable storage medium of claim 13 , wherein the bitstream further comprises a Sequence Parameter Set (SPS), and the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

in response to at least one of a PTL syntax structure, a decoded picture buffer (DPB) parameters syntax structure, or a hypothetical reference decoder (HRD) parameters syntax structure being present in the SPS, determining whether a first value specifying a maximum number of temporal sublayers being present in each coded layer video sequence (CLVS) referring to the SPS is greater than one; and

in response to the first value being greater than one, decoding a flag configured to control a presence of syntax elements in the DPB parameters syntax structure in the SPS.

19. The non-transitory computer-readable storage medium of claim 18 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

in response to the first value being equal to or smaller than one, inferring the flag equal to zero and decoding one or more syntax elements in the DPB parameters syntax structure without decoding the flag in the SPS.

20. The non-transitory computer-readable storage medium of claim 13 , wherein the set of instructions that are executable by the one or more processors of the device causes the device to further perform:

determining a value of a first Sequence Parameter Set (SPS) syntax element, the first SPS syntax element specifying an identifier of the VPS referred to by a SPS when the value of the first SPS syntax element is greater than zero; and

decoding a second SPS syntax element specifying a maximum number of temporal sublayers present in each coded layer video sequence (CLVS) referring to the SPS, a range of the second SPS syntax element being based on a corresponding VPS syntax element of the VPS referred to by the SPS when the value of the first SPS syntax element is greater than zero, or being based on a fixed value when the value of the first SPS syntax element is equal to zero.