Signaling of merge indices for triangle partitions
Different implementations are described, particularly implementations for video encoding and decoding are presented. Accordingly, the encoding or decoding comprises obtaining a merging candidate index that enables deriving both a first merging candidate index and a second merging candidate index in a triangular shape based motion compensation candidates list in list in use in a triangular shape based motion compensation. According to a particular characteristic, a mapping function determines the derivation process of both indices among a subset of possible combinations of merge candidate indices.
1. A method for decoding, comprising:
decoding a syntax element representative of a first merging candidate index of a triangular shape based motion compensation candidates list;
if a number of candidates in the triangular shape based motion compensation candidates list is larger than 2, then a signaling of a second merging candidate index in the triangular shape based motion compensation candidates list is skipped and a second merging candidate index in the triangular shape based motion compensation candidates list is derived from the first merging candidate index using a mapping function; and
decoding a block of a picture by performing a triangular shape based motion compensation using motion information of a merging candidate at a position indicated by the first merging candidate index in the triangular shape based motion compensation candidates list and of a merging candidate at a position indicated by the second merging candidate index in the triangular shape based motion compensation candidates list.
2. The method of claim 1 , wherein a syntax element indicates to which index in the triangular shape based motion compensation candidates list the first merging candidate index corresponds.
3. The method of claim 1 , wherein the mapping function sets the second merging candidate index to one if the first merging candidate index is equal to zero, else sets the second merging candidate index to zero.
4. The method of claim 1 , wherein the mapping function sets the second merging candidate index to one if the first merging candidate index is equal to zero, else sets the second merging candidate index to half the first merging candidate index.
5. The method of claim 1 , wherein the first merging candidate index of a triangular shape based motion compensation candidates list further indicates one of a split direction of a diagonal boundary or an angle and a distance of a slanted boundary.
6. An apparatus for decoding, comprising one or more processors, wherein the one or more processors are configured for:
decoding a syntax element representative of a first merging candidate index of a triangular shape based motion compensation candidates list;
if a number of candidates in the triangular shape based motion compensation candidates list is larger than 2, then a signaling of a second merging candidate index in the triangular shape based motion compensation candidates list is skipped and deriving a second merging candidate index in the triangular shape based motion compensation candidates list is derived from the first merging candidate index using a mapping function; and
decoding a block of a picture by performing a triangular shape based motion compensation using motion information of a merging candidate at a position indicated by the first merging candidate index in the triangular shape based motion compensation candidates list and of a merging candidate at a position indicated by the second merging candidate index in the triangular shape based motion compensation candidates list.
7. The apparatus of claim 6 , wherein a syntax element indicates to which index in the triangular shape based motion compensation candidates list the first merging candidate index corresponds.
8. The apparatus of claim 6 , wherein the mapping function sets the second merging candidate index is set to one if the first merging candidate index is equal to zero, else sets the second merging candidate index is set to zero.
9. The apparatus of claim 6 , wherein the mapping function sets the second merging candidate index is set to one if the first merging candidate index is equal to zero, else sets the second merging candidate index is set to half the first merging candidate index.
10. The apparatus of claim 6 , wherein the first merging candidate index of a triangular shape based motion compensation candidates list further indicates one of a split direction of a diagonal boundary or an angle and a distance of a slanted boundary.
11. A method for encoding, comprising:
if a number of candidates in the triangular shape based motion compensation candidates list is larger than 2, then determining a first merging candidate index of a triangular shape based motion compensation candidates list, wherein a signaling of a second merging candidate index in the triangular shape based motion compensation candidates list is skipped and wherein the first merging candidate index enables deriving the second merging candidate index in the triangular shape based motion compensation candidates list using a mapping function;
encoding a block of a picture by performing a triangular shape based motion compensation using motion information of a merging candidate at a position indicated by the first merging candidate index in the triangular shape based motion compensation candidates list and of a merging candidate at a position indicated by the second merging candidate index in the triangular shape based motion compensation candidates list; and
encoding a syntax element representative of the first merging candidate index of a triangular shape based motion compensation candidates list.
12. The method of claim 11 , wherein a syntax element indicates to which index in the triangular shape based motion compensation candidates list the first merging candidate index corresponds.
13. The method of claim 11 , wherein the mapping function sets the second merging candidate index to one if the first merging candidate index is equal to zero, else sets the second merging candidate index to zero.
14. The method of claim 11 , wherein the mapping function sets the second merging candidate index is set to one if the first merging candidate index is equal to zero, else sets the second merging candidate index to half the first merging candidate index.
15. An apparatus for encoding, comprising one or more processors, wherein the one or more processors are configured for:
if a number of candidates in the triangular shape based motion compensation candidates list is larger than 2, then determining a first merging candidate index of a triangular shape based motion compensation candidates list, wherein a signaling of a second merging candidate index in the triangular shape based motion compensation candidates list is skipped and wherein the first merging candidate index enables deriving the second merging candidate index in the triangular shape based motion compensation candidates list using a mapping function;
encoding a block of a picture by performing a triangular shape based motion compensation using motion information of a merging candidate at a position indicated by the first merging candidate index in the triangular shape based motion compensation candidates list and of a merging candidate at a position indicated by the second merging candidate index in the triangular shape based motion compensation candidates list; and
encoding a syntax element representative of the first merging candidate index of a triangular shape based motion compensation candidates list.
16. The apparatus of claim 15 , wherein a syntax element indicates to which index in the triangular shape based motion compensation candidates list the first merging candidate index corresponds.
17. The apparatus of claim 15 , wherein the mapping function sets the second merging candidate index is set to one if the first merging candidate index is equal to zero, else sets the second merging candidate index is set to zero.
18. The apparatus of claim 15 , wherein the mapping function sets the second merging candidate index to one if the first merging candidate index is equal to zero, else sets the second merging candidate index to half the first merging candidate index.
19. A non-transitory computer readable medium storing data content generated according to the encoding method of claim 11 .
20. A non-transitory computer readable medium storing software code instructions for performing the method according to claim 1 when the instructions are executed by a processor.