Methods and apparatuses of syntax signaling and referencing constraint in video coding system
Encoding methods and apparatuses comprise determining parameters of a specific process for a current slice, signaling in one or more Adaptive Parameter Sets (APSs), performing the specific process using the parameters, signaling an APS ID of each signaled APS in a slice header, and encoding the current slice. Each APS is classified into a category according to a type of data carried by the APS. The APS ID of each signaled APS is counted in a category associated with the specific process and is independent of other categories. Decoding methods and apparatuses comprise parsing an APS ID of each referenced APS from a slice header of a current slice for a specific process, determining parameters from each referenced APS according to the parsed APS ID and a category associated with the specific process, performing the specific process on the current slice and decoding the current slice.
1. A method of decoding video data in a video coding system, comprising:
receiving input data associated with a current slice;
parsing an Adaptive Parameter Set (APS) Identifier (ID) of each referenced APS from a slice header of the current slice for performing a specific process associated with only one category selected among multiple categories, wherein only the APSs classified under the only one category are referenced, wherein the multiple categories correspond to an Adaptive Loop Filter (ALF) process and a Luma Mapping Chroma Scaling (LMCS) process, wherein each APS referenced by the current slice is restricted to include corresponding data or parameters for the specific process associated with the only one category;
determining each referenced APS according to the parsed APS ID and the only one category associated with the specific process, wherein each available APS is classified into one of the multiple categories according to a data type of data carried in the APS, and the APS ID of one APS among each referenced APS is counted in the category only and is independent of other categories;
determining parameters of the specific process for the current slice by referencing one or more of the referenced APSs, wherein when the specific process corresponds to the ALF process, at least one of at least two flags among the parameters of the specific process is constrained to be equal to one;
performing the specific process on one or more blocks in the current slice using the parameters; and
decoding the current slice.
2. The method of claim 1 , wherein the parameters of the ALF process are determined by referencing one or more APSs in a category associated with the ALF process and the parameters of the LMCS process are determined by referencing one or more APSs in a category associated with the LMCS process.
3. The method of claim 1 , wherein all APSs in one category have a same APS parameter type and the APS parameter type of each referenced APS is parsed from the referenced APS.
4. The method of claim 3 , wherein each referenced APS is searched by the APS ID parsed from the slice header and the APS parameter type associated with the specific process.
5. The method of claim 1 , wherein the APS ID of each referenced APS is parsed from a slice header of the current slice or a picture header of a current picture, wherein the current slice is in the current picture.
6. An apparatus for performing video coding, comprising: a computer processor configured for receiving video data; and programming executable on the computer processor for video coding by performing steps comprising:
receiving input data associated with a current slice;
signaling or parsing an APS Identifier (ID) of each referenced Adaptive Parameter Set (APS) from a slice header of the current slice for performing a specific process associated with only one category selected among multiple categories, wherein only the APSs classified under the only one category are referenced, wherein the multiple categories correspond to an Adaptive Loop Filter (ALF) process and a Luma Mapping Chroma Scaling (LMCS) process, wherein each APS referenced by the current slice is restricted to include corresponding data or parameters for the specific process associated with the only one category;
determining each referenced APS according to the signaled or parsed APS ID and the only one category associated with the specific process, wherein each available APS is classified into one of the multiple categories according to a data type of data carried in the APS, and the APS ID of one APS among each referenced APS is counted in the category only and is independent of other categories;
determining parameters of the specific process for the current slice by referencing one or more of the referenced APSs, wherein when the specific process corresponds to the ALF process, at least one of at least two flags among the parameters of the specific process is constrained to be equal to one;
performing the specific process on one or more blocks in the current slice using the parameters; and
encoding or decoding the current slice.
7. The apparatus of claim 6 , wherein the parameters of the ALF process are determined by referencing one or more APSs in a category associated with the ALF process and the parameters of the LMCS process are determined by referencing one or more APSs in a category associated with the LMCS process.
8. The apparatus of claim 6 , wherein all APSs in one category have a same APS parameter type and the APS parameter type of each referenced APS is parsed from the referenced APS.
9. The apparatus of claim 8 , wherein each referenced APS is searched by the APS ID parsed from the slice header and the APS parameter type associated with the specific process.
10. The apparatus of claim 6 , wherein the APS ID of each referenced APS is parsed from a slice header of the current slice or a picture header of a current picture, wherein the current slice is in the current picture.
11. The method of claim 1 , further comprising checking if each APS referenced by the current slice includes corresponding data or parameters for the specific process, and modifying or removing the APS ID of any APS without corresponding data or parameters from the slice header of the current slice, wherein the step of determining each referenced APS according to the parsed APS ID and the only one category associated with the specific process is performed after at least one of the checking, modifying and removing steps.
12. The method of claim 1 , wherein said at least two flags among the parameters of the specific process correspond to at least a flag related to luma and at least a flag related to chroma.