Method and a device for picture encoding and decoding

1. A method comprising:

decoding a single information set signaled in a first portion of video data, the single information set containing a plurality of candidate sets of filter parameters, a filter parameter comprising an absolute value of the filter parameter and a sign of the filter parameter;

obtaining from the video data, for a current block, at least one index identifying one of the candidate sets of filter parameters in the single information set;

decoding the current block from a second portion of the video data different from the first portion; and

filtering the decoded current block using the candidate set of filter parameters identified by the at least one index.

2. The method of claim 1 , wherein the single information set is signaled for a block decoded first in decoding order.

3. The method according to claim 1 , comprising obtaining data representative of a number of candidate sets of filter parameters in the plurality of candidate sets of filter parameters from the single information set.

4. The method according to claim 1 , wherein the candidate sets of the plurality of candidate sets of filter parameters are represented in their order of use in the single information set.

5. The method according to claim 1 , further comprising re-ordering the candidate sets of filter parameters before filtering the current block.

6. The method of claim 5 , wherein the candidate sets of filter parameters are re-ordered such that the set of filter parameters used for filtering a block located immediately to the left of the current block, when such a block is available, is listed first.

7. The method of claim 5 , wherein the candidate sets of filter parameters are re-ordered such that the candidate sets of filter parameters used for filtering blocks decoded prior to the current block are listed in an order that depends on a spatial distance between the block decoded prior to the current block and the current block.

8. The method according to claim 5 , wherein the candidate sets of filter parameters are re-ordered such that at least one candidate set of filter parameters not used for filtering blocks decoded prior to the current block is inserted before a last candidate set of filter parameters used for filtering the blocks decoded prior to the current block.

9. The method according to claim 5 , wherein the candidate sets of filter parameters are re-ordered such that a candidate set of filter parameters not used by blocks decoded prior to the current block and that is the first candidate to be used next is inserted at a position that is a function of a number of blocks of the picture part to decode after the current block and of the number of candidate sets of filter parameters not used yet by blocks decoded prior to the current block.

10. The method according to claim 1 , further comprising inserting, in the plurality of candidate sets of filter parameters, a candidate set of filter parameters specifying that a block is not filtered.

11. The method of claim 10 , wherein the candidate set of filter parameters specifying that a block is not filtered is inserted between the candidate sets of filter parameters at a predefined position.

12. A method comprising:

determining a reconstructed block comprising a reconstructed version of a current block;

obtaining a plurality of candidate sets of filter parameters;

representing the plurality of candidate sets of filter parameters in a single information set; and

determining at least one index in the single information set for the current block, each index identifying one of the candidate sets of filter parameters in the single information set, a filter parameter comprising an absolute value of the filter parameter and a sign of the filter parameter;

filtering the reconstructed block with the candidate set of filter parameters of the plurality of candidate sets of filter parameters identified by the at least one index; and

encoding in video data:

the single information set in a first portion of the video data;

data representative of the current block in a second portion of the video data different from the first portion; and

data representative of the at least one index.

13. The method of claim 12 , wherein the single information set is encoded in a slice header of a slice to which the current block belongs.

14. The method of claim 12 , wherein the single information set is associated with a block of the picture part encoded first in encoding order.

15. The method according to claim 12 , wherein the single information set comprises data representative of a number of candidate sets of filter parameters in the plurality of candidate sets of filter parameters.

16. The method according to claim 12 , wherein the candidate sets of the plurality of candidate sets of filter parameters are encoded in their order of use in the single information set.

17. The method according to claim 12 , further comprising re-ordering the candidate sets of filter parameters before coding the current block.

18. A decoder comprising:

at least one processor configured to:

decode a single information set signaled in a first portion of video data containing a plurality of candidate sets of filter parameters, a filter parameter comprising an absolute value of the filter parameter and a sign of the filter parameter;

obtain from the video data, for a current block, at least one index identifying one of the candidate sets of filter parameters in the single information set;

decode the current block from a second portion of the video data different from the first portion; and

filter the decoded current block with the candidate set of filter parameters identified by the at least one index.

19. The decoder of claim 18 , wherein the single information set is signaled for a block decoded first in decoding order.

20. The decoder according to claim 18 , wherein the at least one processor is further configured to obtain data representative of a number of candidate sets of filter parameters in the plurality of candidate sets of filter parameters from the single information set.

21. The decoder according to claim 18 , wherein the candidate sets of the plurality of candidate sets of filter parameters are signalled in their order of use in the single information set.

22. The decoder according to claim 18 , wherein the at least one processor is further configured to re-order the candidate sets of filter parameters before filtering the current block.

23. The decoder of claim 22 , wherein the candidate sets of filter parameters are re-ordered such that the set of filter parameters used for filtering a block located immediately to the left of the current block, when such a block is available, is listed first.

24. The decoder of claim 22 , wherein the candidate sets of filter parameters are re-ordered such that the candidate sets of filter parameters used for filtering blocks decoded prior to the current block are listed in an order that depends on a spatial distance between the block decoded prior to the current block and the current block.

25. The decoder according to claim 22 , wherein the candidate sets of filter parameters are re-ordered such that at least one candidate set of filter parameters not used for filtering blocks decoded prior to the current block is inserted before a last candidate set of filter parameters used for filtering the blocks decoded prior to the current block.

26. The decoder according to claim 22 , wherein the candidate sets of filter parameters are re-ordered such that a candidate set of filter parameters not used by blocks decoded prior to the current block and that is the first candidate to be used next is inserted at a position that is a function of a number of blocks of the picture part to decode after the current block and of the number of candidate sets of filter parameters not used yet by blocks decoded prior to the current block.

27. The decoder according to claim 18 , wherein the at least one processor is further configured to insert, in the plurality of candidate sets of filter parameters, a candidate set of filter parameters specifying that a block is not filtered.

28. The decoder of claim 27 , wherein the candidate set of filter parameters specifying that a block is not filtered is inserted between the candidate sets of filter parameters at a predefined position.

29. An encoder comprising:

at least one processor configured to:

determine a reconstructed block comprising a reconstructed version of a current block;

obtain a plurality of candidate sets of filter parameters;

represent the plurality of candidate sets of filter parameters in a single information set; and

determine an index in the single information set for the current block, the index identifying one of the candidate sets of filter parameters in the single information set, a filter parameter comprising an absolute value of the filter parameter and a sign of the filter parameter;

filter the reconstructed block with the candidate set of filter parameters of the plurality of candidate sets of filter parameters identified by the index; and

encode in video data:

the single information set in a first portion of the video data;

data representative of the current block in a second portion of the video data different from the first portion; and

data representative of the index.

30. The encoder of claim 29 , wherein the single information set is encoded in a slice header of a slice to which the current block belongs.

31. The encoder of claim 29 , wherein the single information set is associated with a block of the picture part encoded first in encoding order.

32. The encoder according to claim 29 , wherein the at least one processor is further configured to signal in the single information set data representative of a number of candidate sets of filter parameters in the plurality of candidate sets of filter parameters.

33. The encoder according to claim 29 , wherein the candidate sets of the plurality of candidate sets of filter parameters are signalled in their order of use in the single information set.

34. The encoder according to claim 29 , wherein the at least one processor is further configured to re-order the candidate sets of filter parameters before coding the current block.

35. The method of claim 1 , wherein the single information set is decoded from a slice header of a slice to which the current block belongs.

36. The decoder of claim 18 , wherein the at least one processor is further configured to decode the single information set from a slice header of a slice to which the current block belongs.