Method and apparatus of multi-hypothesis in video coding

1. A method of prediction for video coding, the method comprising:

receiving input data related to a current block in a current picture at a video encoder side or a video bitstream corresponding to compressed data including the current block in the current picture at a video decoder side;

partitioning the current block into a first partition and a second partition;

determining a first candidate for the first partition and a second candidate for the second partition, wherein at least one of the first candidate and the second candidate is derived using a candidate list derived for a normal Merge mode;

generating an MH prediction by blending a first prediction corresponding to the first candidate and a second prediction corresponding to the second candidate, and wherein the MH prediction is applied to a part of the current block; and

encoding the current block or current motion information associated with the current block using at least one of the first candidate and the second candidate at the video encoder side, or decoding the current block or the current motion information associated with the current block at the video decoder side using at least one of the first candidate and the second candidate.

2. The method of claim 1 , wherein the current block is partitioned into two triangles along a diagonal line from a lower-left corner to an upper-right corner of the current block or from an upper-left corner to a lower-right corner of the current block.

3. The method of claim 1 , wherein the current block is partitioned into two sub-blocks in a horizontal direction, a vertical direction, or an angular direction based on directional information.

4. The method of claim 3 , wherein the directional information corresponds to 45 degrees or 135 degrees.

5. The method of claim 1 , wherein the first candidate is derived from a first candidate list associated with the candidate list derived for the normal Merge mode.

6. The method of claim 5 , wherein the second candidate is derived from a second candidate list associated with the candidate list derived for the normal Merge mode.

7. The method of claim 6 , wherein the first candidate list and the second candidate list share a same candidate list.

8. The method of claim 1 , wherein the first candidate and the second candidate are derived from the same candidate list.

9. The method of claim 1 , wherein the first candidate, the second candidate or both are selected based on an index of the first candidate, an index of the second candidate or both.

10. The method of claim 9 , wherein List 0 or List 1 motion information of the first candidate or the second candidate is selected based on the index of the first candidate or the index of the second candidate.

11. The method of claim 9 , wherein when motion information selected for the first candidate and the second candidate is the same, the motion information for the first candidate or the second candidate is not modified.

12. The method of claim 1 , wherein one candidate index is derived for each of the first partition and the second partition.

13. The method of claim 1 , wherein candidate members in front of the candidate list are assigned shorter-length codewords.

14. The method of claim 1 , wherein one candidate index is signalled for each of the first partition and the second partition.

15. The method of claim 14 , wherein signalling of at least one of the candidate index for partition 1 and the candidate index for partition 2 is the same as signalling of Merge index for the normal Merge mode.

16. The method of claim 14 , wherein ordering of candidate members in the candidate list is based on a fixed order similar to or the same as that for the normal Merge mode.

17. An apparatus of video coding, the apparatus comprising one or more electronic circuits or processors arranged to:

receive input data related to a current block in a current picture at a video encoder side or a video bitstream corresponding to compressed data including the current block in the current picture at a video decoder side;

partition the current block into a first partition and a second partition;

determine a first candidate for the first partition and a second candidate for the second partition, wherein at least one of the first candidate and the second candidate is derived using a candidate list derived for a normal Merge mode;

generate an MH prediction by blending a first prediction corresponding to the first candidate and a second prediction corresponding to the second candidate, and wherein the MH prediction is applied to a part of the current block; and

encode the current block or current motion information associated with the current block using at least one of the first candidate and the second candidate at the video encoder side, or decode the current block or the current motion information associated with the current block at the video decoder side using at least one of the first candidate and the second candidate.