Parameter set coding

1. A method comprising:

forming a plurality of syntax element assignments, each syntax element assignment relating to a subset of syntax elements of a set of syntax elements, and each syntax element assignment comprising assignments of values to said related subset of syntax elements,

forming an index for each of said plurality of syntax element assignments,

forming a plurality of combination parameter sets, each combination parameter set comprising a plurality of indexes of said syntax element assignments, wherein at least one syntax element assignment applies to zero syntax elements, and

encoding at least one said combination parameter set into a video bitstream for determining parameter values for video decoding.

2. A method according to claim 1 , comprising:

forming a combination parameter set index for each of said plurality of combination parameter sets, and

encoding at least one said combination parameter set index into a video bitstream for determining parameter values for video decoding.

3. A method according to claim 1 , comprising:

determining a combination parameter set to be used according to picture parameters, wherein determining the combination parameter set comprises deriving an identifier of the combination parameter set from a slice header syntax, and

encoding an indication into a video bitstream indicating that a combination parameter set index is not encoded into slice headers of the video bitstream, and that the combination parameter set to be used is to be determined from picture parameters, said picture parameters comprising parameters remaining unchanged for one or more pictures.

4. A method according to claim 1 , comprising:

encoding an indicator into the video bitstream that combination parameter sets are to be used, and

encoding said combination parameter sets to a header parameter set, said header parameter set comprising slice header syntax elements.

5. A method according to claim 1 , comprising:

encoding an indicator into the video bitstream in a slice header that combination parameter sets are to be used, and

encoding an identifier of at least one said combination parameter set to a slice header.

6. A method comprising:

decoding from a video bitstream a plurality of syntax element assignments, each syntax element assignment relating to a subset of syntax elements of a set of syntax elements, and each syntax element assignment comprising assignments of values to said related subset of syntax elements,

decoding from said video bitstream an index for each of said plurality of syntax element assignments,

decoding from said video bitstream a plurality of combination parameter sets, each combination parameter set comprising a plurality of indexes of syntax element assignments, wherein at least one syntax element assignment applies to zero syntax elements, and

decoding from said video bitstream at least one said combination parameter set for determining parameter values for video decoding.

7. A method according to claim 6 , comprising:

decoding from said video bitstream combination parameter set indexes, each index for identifying one of said plurality of combination parameter sets, and

decoding from said video bitstream at least one said combination parameter set index for determining parameter values for video decoding.

8. A method according to claim 6 , comprising:

determining a combination parameter set to be used according to picture parameters, wherein determining the combination parameter set comprises deriving an identifier of the combination parameter set from a slice header syntax,

decoding from said video bitstream an indication indicating that a combination parameter set index is not encoded into slice headers of the video bitstream, and

determining the combination parameter set to be used from picture parameters, said picture parameters comprising parameters remaining unchanged for one or more pictures.

9. A method according to claim 8 , comprising:

determining a combination parameter set to be used from a picture order count syntax element.

10. A method according to claim 6 , comprising:

decoding from said video bitstream an indicator that combination parameter sets are to be used, and

decoding from said video bitstream said combination parameter sets from a header parameter set, said header parameter set comprising slice header syntax elements.

11. A method according to claim 6 , comprising:

decoding from said video bitstream an indicator in a slice header that combination parameter sets are to be used, and

decoding from said video bitstream an identifier of at least one said combination parameter set from a slice header.

12. An apparatus comprising at least one processor and memory, said memory containing computer program code, said computer program code being configured to, when executed on the at least one processor, cause the apparatus to:

form a plurality of syntax element assignments, each syntax element assignment relating to a subset of syntax elements of a set of syntax elements, and each syntax element assignment comprising assignments of values to said related subset of syntax elements,

form an index for each of said plurality of syntax element assignments,

form a plurality of combination parameter sets, each combination parameter set comprising a plurality of indexes of syntax element assignments, wherein at least one syntax element assignment applies to zero syntax elements, and

encode at least one said combination parameter set into a video bitstream for determining parameter values for video decoding.

13. An apparatus according to claim 12 , comprising computer program code to cause the apparatus to:

form a combination parameter set index for each of said plurality of combination parameter sets, and

encode at least one said combination parameter set index into a video bitstream for determining parameter values for video decoding.

14. An apparatus according to claim 12 , comprising computer program code to cause the apparatus to:

determine a combination parameter set to be used according to picture parameters, wherein determining the combination parameter set comprises deriving an identifier of the combination parameter set from a slice header syntax, and

encode an indication into a video bitstream indicating that a combination parameter set index is not encoded into slice headers of the video bitstream, and that the combination parameter set to be used is to be determined from picture parameters, said picture parameters comprising parameters remaining unchanged for one or more pictures.

15. An apparatus comprising at least one processor and memory, said memory containing computer program code, said computer program code being configured to, when executed on the at least one processor, cause the apparatus to:

decode from a video bitstream a plurality of syntax element assignments, each syntax element assignment relating to subset of syntax elements of a set of syntax elements, and each syntax element assignment comprising assignments of values to said related subset of syntax elements,

decode from said video bitstream an index for each of said plurality of syntax element assignments,

decode from said video bitstream a plurality of combination parameter sets, each combination parameter set comprising a plurality of indexes of syntax element assignments, wherein at least one syntax element assignment applies to zero syntax elements, and

decode from said video bitstream at least one said combination parameter set for determining parameter values for video decoding.

16. An apparatus according to claim 15 , comprising computer program code to cause the apparatus to:

decode from said video bitstream combination parameter set indexes, each index for identifying one of said plurality of combination parameter sets, and

decode from said video bitstream at least one said combination parameter set index for determining parameter values for video decoding.

17. An apparatus according to claim 15 , comprising computer program code to cause the apparatus to:

determine a combination parameter set to be used according to picture parameters, wherein determining the combination parameter set comprises deriving an identifier of the combination parameter set from a slice header syntax,

decode from said video bitstream an indication indicating that a combination parameter set index is not encoded into slice headers of the video bitstream, and

determine the combination parameter set to be used from picture parameters, said picture parameters comprising parameters remaining unchanged for one or more pictures.

18. An apparatus according to claim 17 , comprising computer program code to cause the apparatus to:

determining a combination parameter set to be used from a picture order count syntax element.

19. A computer program product embodied on a non-transitory computer readable media, said computer program product including one or more sequences of one or more instructions which, when executed by one or more processors, cause an apparatus or module to at least perform the following:

form a plurality of syntax element assignments, each syntax element assignment relating to a subset of syntax elements of a set of syntax elements, and each syntax element assignment comprising assignments of values to said related subset of syntax elements,

form an index for each of said plurality of syntax element assignments,

form a plurality of combination parameter sets, each combination parameter set comprising a plurality of indexes of syntax element assignments, wherein at least one syntax element assignment applies to zero syntax elements, and

encode at least one said combination parameter set into a video bitstream for determining parameter values for video decoding.

20. A computer program product embodied on a non-transitory computer readable media, said computer program product including one or more sequences of one or more instructions which, when executed by one or more processors, cause an apparatus or module to at least perform the following:

decode from a video bitstream a plurality of syntax element assignments, each syntax element assignment relating to a subset of syntax elements of a set of syntax elements, and each syntax element assignment comprising assignments of values to said related subset of syntax elements,

decode from said video bitstream an index for each of said plurality of syntax element assignments,

decode from said video bitstream a plurality of combination parameter sets, each combination parameter set comprising a plurality of indexes of said syntax element assignments, wherein at least one syntax element assignment applies to zero syntax elements, and

decode from said video bitstream at least one said combination parameter set for determining parameter values for video decoding.