Picture coding supporting block partitioning and block merging
A further coding efficiency increase may be achieved if for a current block of a picture, for which the bit stream signals one of supported partitioning patterns, a reversal of the partitioning by block merging is avoided. In particular, if the signaled one of the supported partitioning patterns specifies a subdivision of the block into two or more further blocks, a removal of certain coding parameter candidates for all further blocks, except a first further block of the further blocks in a coding order, is performed. Particularly, those coding parameter candidates are removed from the set of coding parameter candidates for the respective further block, the coding parameters of which are the same as coding parameters associated with any of the further blocks which, when being merged with the respective further block, would result in one of the supported partitioning pattern. This avoids redundancy between partitioning coding and merging coding.
1. A decoder configured to decode a bitstream signaling one of supported partitioning patterns for a current block of a picture, the decoder being configured to:
if the signaled one of the supported partitioning patterns specifies a subdivision of the current block into a plurality of sub-blocks,
remove, for a sub-block except a first sub-block of the sub-blocks in a coding order, from a set of coding parameter candidates for the respective sub-block, a coding parameter candidate associated with a candidate block, wherein the candidate block, when merged with the respective sub-block, results in one of the supported partitioning patterns,
wherein the decoder is configured to:
determine coding parameter candidates for a current sub-block of the sub-blocks,
check whether a total number of determined coding parameter candidates is equal to a predetermined number of coding parameter candidates needed to complete the set of coding parameter candidates for the current sub-block, and
based on an indication from the check that the total number of determined coding parameter candidates is not equal to the predetermined number of coding parameter candidates, provide one or more ancillary coding parameter candidates including a zero motion vector parameter to the set of coding parameter candidates to complete the set.
2. The decoder according to claim 1 , wherein the one or more ancillary coding parameter candidates include parameters of neighboring partitions of temporally neighboring and previously coded pictures.
3. The decoder according to claim 1 , wherein the one or more ancillary coding parameter candidates include a combined coding parameter candidate obtained by combination of coding parameters associated with previously decoded blocks neighboring the current sub-block.
4. The decoder according to claim 1 , wherein the decoder is configured to, depending on the total number of coding parameter candidates in the set of coding parameter candidates being greater than one, decode a syntax element from the bitstream specifying which of the predetermined number of coding parameter candidates is to be used for merging.
5. The decoder according to claim 1 , wherein the decoder is configured to, if the signaled one of the supported partitioning patterns specifies a subdivision of the block into two sub-blocks, remove for a second sub-block of the sub-blocks in the coding order, from the set of coding parameter candidates for the second sub-block, coding parameter candidates having coding parameters which are the same as coding parameters associated with the first sub-block of the sub-blocks in the coding order.
6. The decoder according to claim 1 , wherein the picture has associated therewith a depth map as additional information.
7. The decoder according to claim 1 , wherein the picture includes samples arrays related to different planes of the picture, which are coded independently from each other.
8. An encoder configured to encode a picture into a bitstream, the encoder being configured to:
signaling, within a bitstream, one of supported partitioning patterns for a current block; and
if the signaled one of the supported partitioning patterns specifies a subdivision of the current block into a plurality of sub-blocks,
remove, for a sub-block except a first sub-block of the sub-blocks in a coding order, from a set of coding parameter candidates for the respective sub-block, a coding parameter candidate associated with a candidate block, wherein the candidate block, when merged with the respective sub-block, results in one of the supported partitioning patterns,
wherein the encoder is configured to:
determine coding parameter candidates for a current sub-block of the sub-blocks,
check whether a total number of determined coding parameter candidates is equal to a predetermined number of coding parameter candidates needed to complete the set of coding parameter candidates for the current sub-block, and
based on an indication from the check that the total number of determined coding parameter candidates is not equal to the predetermined number of coding parameter candidates, provide one or more ancillary coding parameter candidates including a zero motion vector parameter to the set of coding parameter candidates to complete the set.
9. The encoder according to claim 8 , wherein the one or more ancillary coding parameter candidates include parameters of neighboring partitions of temporally neighboring and previously coded pictures.
10. The encoder according to claim 8 , wherein the one or more ancillary coding parameter candidates include a combined coding parameter candidate obtained by combination of coding parameters associated with previously decoded blocks neighboring the current sub-block.
11. The encoder according to claim 8 , wherein the encoder is configured to, if the signaled one of the supported partitioning patterns specifies a subdivision of the block into two sub-blocks, remove for a second sub-block of the sub-blocks in the coding order, from the set of coding parameter candidates for the second sub-block, coding parameter candidates having coding parameters which are the same as coding parameters associated with the first sub-block of the sub-blocks in the coding order.
12. The encoder according to claim 8 , wherein the picture has associated therewith a depth map as additional information.
13. The encoder according to claim 8 , wherein the picture includes samples arrays related to different planes of the picture, which are coded independently from each other.
14. The encoder according to claim 8 , wherein the encoder is configured to derive at least one coding parameter candidate of the set based on a combination of coding parameters of two previously coded blocks.
15. The decoder according to claim 1 , wherein the decoder is configured to derive at least one coding parameter candidate of the set based on a combination of coding parameters of two previously decoded blocks.
16. A method for decoding a data stream, comprising:
obtaining, in the data stream, data signaling one of supported partitioning patterns for a current block of a picture;
determining that the signaled one of the supported partitioning patterns specifies a subdivision of the current block into a plurality of sub-blocks;
removing, for a sub-block except a first sub-block of the sub-blocks in a coding order, from a set of coding parameter candidates for the respective sub-block, a coding parameter candidate associated with a candidate block, wherein the candidate block, when merged with the respective sub-block, results in one of the supported partitioning patterns;
determining coding parameter candidates for a current sub-block of the sub-blocks;
checking whether a total number of determined coding parameter candidates is equal to a predetermined number of coding parameter candidates needed to complete the set of coding parameter candidates for the current sub-block; and
based on an indication from the check that the total number of determined coding parameter candidates is not equal to the predetermined number of coding parameter candidates, providing one or more ancillary coding parameter candidates including a zero motion vector parameter to the set of coding parameter candidates to complete the set.
17. The method according to claim 16 , wherein the one or more ancillary coding parameter candidates include parameters of neighboring partitions of temporally neighboring and previously coded pictures.
18. The method according to claim 16 , wherein the one or more ancillary coding parameter candidates include a combined coding parameter candidate obtained by combination of coding parameters associated with previously decoded blocks neighboring the current sub-block.
19. The method according to claim 16 , wherein the picture has associated therewith a depth map as additional information.
20. The method according to claim 16 , wherein the picture includes samples arrays related to different planes of the picture, which are coded independently from each other.
21. A method for storing a data stream, comprising storing, on a digital storage medium, a data stream which is decoded into a picture by a method according to claim 16 .