Encoder, a decoder and corresponding methods of signaling and semantics in parameter sets

1. A method of decoding a video bitstream implemented by a decoding device, the method comprising:

obtaining a value of a first syntax element from a sequence parameter set (SPS), wherein the value of the first syntax element is used to specify whether a decoded picture buffer (DPB) parameters syntax structure is present in the SPS, wherein the SPS is coded in the video bitstream and contains syntax elements that apply to a video sequence; and

obtaining a value of a second syntax element from the SPS, at least when determining that the value of the first syntax element specifies that the DPB parameters syntax structure is present in the SPS, wherein the value of the second syntax element is used to specify presence of a DPB syntax element in the DPB parameters syntax structure, wherein the DPB syntax element is applied to a temporal sublayer except for a highest temporal sublayer in the video sequence.

2. The method of claim 1 , further comprising:

obtaining a value of the DPB syntax element based on the value of the second syntax element; and

reconstructing the video sequence based on the value of the DPB syntax element.

3. The method of claim 2 , wherein the obtaining the value of the DPB syntax element based on the value of the second syntax element comprises:

obtaining the value of the DPB syntax element from the DPB parameters syntax structure, when determining that the value of the second syntax element specifies that the DPB syntax element is present in the DPB parameters syntax structure; or

setting the value of the DPB syntax element equal to a value of another DPB syntax element applied to the highest temporal sublayer in the DPB parameters syntax structure, when determining that the value of the second syntax element specifies that the DPB syntax element is not present in the DPB parameters syntax structure.

4. The method of claim 2 , wherein the reconstructing the video sequence based on the value of the DPB syntax element comprises: configuring the DPB based on the value of the DPB syntax element; and reconstructing the video sequence using the DPB.

5. The method of claim 2 , wherein the reconstructing the video sequence based on the value of the DPB syntax element comprises: reconstructing the video sequence based on determining that the DPB used satisfies a requirement specified by the value of the DPB syntax element.

6. The method of claim 1 , further comprising:

obtaining a value of a third syntax element from the SPS, wherein the value of the third syntax element is used to determine a maximum number of temporal sublayers that are present in the video sequence.

7. The method of claim 6 , wherein the obtaining the value of the second syntax element from the SPS comprises:

determining whether the maximum number of the temporal sublayers in the video bitstream is greater than 1 based on the value of the third syntax element, when determining that the value of the first syntax element specifies that the DPB parameters syntax structure is present in the SPS; and

obtaining the value of the second syntax element from the SPS, when determining that the maximum number of the temporal sublayers is greater than one.

8. A method of encoding a video bitstream implemented by an encoding device, the method comprising:

determining presence of a decoded picture buffer (DPB) parameters syntax structure in a sequence parameter set (SPS), wherein the SPS is encoded in the video bitstream and contains syntax elements that apply to a video sequence;

encoding a value of a first syntax element into the SPS based on the determining of the presence of the DPB parameters syntax structure in the SPS, wherein the value of the first syntax element is used to specify whether the DPB parameters syntax structure is present in the SPS;

determining presence of a DPB syntax element in the DPB parameters syntax structure, when determining that the DPB parameters syntax structure is present in the SPS, wherein the DPB syntax element is applied to a temporal sublayer except for a highest temporal sublayer in the video sequence; and

encoding a value of a second syntax element into the SPS based on the determining of the presence of the DPB syntax element in the DPB parameters syntax structure, wherein the value of the second syntax element is used to specify the presence of the DPB syntax element in the DPB parameters syntax structure.

9. The method of claim 8 , further comprising: determining a value of the DPB syntax element when determining that the DPB syntax element is present in the DPB parameters syntax structure; and reconstructing the video sequence based on the value of the DPB syntax element.

10. The method of claim 8 , further comprising: setting the value of the DPB syntax element equal to a value of another DPB syntax element applied to the highest temporal sublayer in the DPB parameters syntax structure; and reconstructing the video sequence based on the value of the DPB syntax element.

11. The method of claim 9 , wherein the reconstructing the video sequence based on the value of the DPB syntax element comprises: configuring the DPB to satisfy the value of the DPB syntax element; and reconstructing the video sequence using the DPB.

12. The method of claim 8 , wherein the presence of a DPB syntax element in the DPB parameters syntax structure is determined, when it is determined that the DPB parameters syntax structure is present in the SPS and a maximum number of temporal sublayers in the video bitstream is greater than one.

13. An apparatus for decoding a coded video bitstream, wherein the apparatus comprises:

an obtaining unit configured to obtain a value of a first syntax element from a sequence parameter set (SPS) coded in the video bitstream, wherein the value of the first syntax element is used to specify whether a decoded picture buffer (DPB) parameters syntax structure is present in the SPS; and

a determining unit configured to determine whether the value of the first syntax element specifies that the DPB parameters syntax structure is present in the SPS; and wherein

the obtaining unit is further configured to obtain a value of a second syntax element from the SPS, at least when determining that the value of the first syntax element specifies that the DPB parameters syntax structure is present in the SPS, wherein the value of the second syntax element is used to specify presence of a DPB syntax element in the DPB parameters syntax structure, wherein the DPB syntax element is applied to a temporal sublayer except for a highest temporal sublayer in a video sequence.

14. An apparatus for encoding a video bitstream, wherein the apparatus comprises:

a determining unit configured to determine presence of a decoded picture buffer (DPB) parameters syntax structure in a sequence parameter set (SPS) encoded in the video bitstream; and

an encoding unit configured to encode a value of a first syntax element into the SPS based on the determining of the presence of the DPB parameters syntax structure in the SPS, wherein the value of the first syntax element is used to specify whether the DPB parameters syntax structure is present in the SPS; wherein

the determining unit is further configured to determine presence of a DPB syntax element in the DPB parameters syntax structure, when determining that the DPB parameters syntax structure is present in the SPS, wherein the DPB syntax element is applied to a temporal sublayer except for a highest temporal sublayer in a video sequence; and wherein

the encoding unit is further configured to encode a value of a second syntax element into the SPS based on the determining of the presence of the DPB syntax element in the DPB parameters syntax structure, wherein the value of the second syntax element is used to specify the presence of the DPB syntax element in the DPB parameters syntax structure.

15. A computer program product embodied on a non-transitory computer-readable medium, the computer program product comprising a program code for performing the method according to claim 1 when executed on a computer or a processor.

16. A decoder, comprising:

one or more processors; and

a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the decoder to carry out the method according to claim 1 .

17. An encoder, comprising:

one or more processors; and

a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the encoder to carry out the method according to claim 8 .

18. A non-transitory computer-readable medium carrying a program code which, when executed by a computer device, causes the computer device to perform the method of claim 1 .

19. A non-transitory storage medium which includes an encoded bitstream, the bitstream being generated by dividing a current picture of a video signal or an image signal into a plurality blocks, and comprising a plurality of syntax elements, wherein the plurality of syntax elements comprises a first syntax element in a sequence parameter set (SPS), wherein the value of the first syntax element is used to specify whether a decoded picture buffer (DPB) parameters syntax structure is present in the SPS; in case that the value of the first syntax element specifies that the DPB parameters syntax structure is present in the SPS, the bitstream further comprises a second syntax element in the SPS, wherein the value of the second syntax element is used to specify presence of a DPB syntax element in the DPB parameters syntax structure, wherein the DPB syntax element is applied to a temporal sublayer except for a highest temporal sublayer in a video sequence.