Method and apparatus for deriving temporal motion vector prediction

1. A method of deriving a motion vector predictor (MVP) for a motion vector (MV) of a current block of a current picture in Inter, or Merge, or Skip mode, wherein the MV is associated with the current block and a corresponding block of a target reference picture in a given reference list, the method comprising:

selecting a co-located block corresponding to a co-located picture;

receiving one or more reference motion vectors (MVs) of one or more co-located reference blocks associated with the co-located block;

determining a search set, wherein the search set comprises one or more search MVs associated with said one or more co-located reference blocks;

determining a search order for the search set, wherein the search order starts with searching the search MV corresponding to the given reference list, if the search MV corresponding to the given reference list is not available, the search order then searches the search MV corresponding to a reference list different from the given reference list;

determining the MVP for the current block based on the search set and the search order; and

providing the MVP for the current block,

wherein said one or more co-located reference blocks comprise an inside co-located block at center of the co-located block and an outside co-located block outside the co-located block across from a lower-right corner of the co-located block;

wherein said determining the MVP searches the search MVs associated with the outside co-located block and then the inside co-located block, and the search order for each co-located reference block is from the search MV corresponding to the given reference list, to the search MV corresponding to a reference list different from the given reference list; and

wherein the search order for determining the MVP is from the search MV corresponding to the given reference list, to the search MV corresponding to a reference list different from the given reference list associated with the outside co-located block; and wherein said determining the MVP further searches the one or more search MVs associated with the inside co-located block if no MVP is found or the MVP found is the same as a previous MVP derived from neighboring blocks of the current block.

2. The method of claim 1 , wherein the co-located picture associated with the co-located block is indicated by a flag, and information associated with the flag is incorporated in sequence level, picture level, or slice level.

3. The method of claim 1 , wherein the co-located picture associated with the co-located block is derived according to an implicit method.

4. The method of claim 3 , wherein selection method for the co-located picture associated with the co-located block is determined according to the given reference list.

5. The method of claim 4 , wherein the selection method selects the co-located picture in a reference list different from the given reference list.

6. The method of claim 1 , wherein selection method for the co-located picture associated with the co-located block is based on a temporal distance associated with said one or more reference MVs of said one or more co-located reference blocks.

7. The method of claim 6 , wherein the selection method selects the co-located block, wherein said one or more reference MVs associated with the co-located block have a shortest temporal distance.

8. The method of claim 1 , wherein selection method for the co-located picture associated with the co-located block is based on a picture type of the co-located picture.

9. The method of claim 1 , wherein selection method for the co-located picture associated with the co-located block is based on a layer of the co-located picture in a hierarchical group of pictures (GOP), or a picture order of the co-located picture in a GOP, or the picture order of the co-located picture in a same layer as the hierarchical GOP.

10. The method of claim 1 , wherein the inside co-located block is located at center of the co-located block.

11. The method of claim 1 , wherein the outside co-located block is located outside the co-located block across from a lower-right corner of the co-located block.

12. The method of claim 1 , wherein said determining the MVP searches the search MVs associated with the outside co-located block before the search MVs associated with the inside co-located block.

13. The method of claim 1 , the MVP is set to zero, a default value or a pre-defined value, or removed from a candidate set of MVPs if no MVP is found or the MVP found is the same as the previous MVP after the search MVs associated with the inside co-located block are searched.

14. The method of claim 1 , wherein said determining the MVP searches the search MV(s) associated with a second co-located reference block if said determining the MVP finds no MVP from the search MV(s) associated with a first co-located block, or if the MVP found is the same as a previous MVP derived from neighboring blocks of the current block.

15. The method of claim 14 , wherein the MVP is set to zero, a default value or a pre-defined value, or removed from a candidate set of MVPs, if no MVP is found or the MVP found is the same as the previous MVP after searching the search MV(s) associated with the co-located reference blocks in the search set.

16. The method of claim 1 , wherein the MVP is scaled according to a first temporal distance associated with the MVP selected and a second temporal distance associated with the motion vector of the current block.

17. An apparatus for deriving a motion vector predictor (MVP) for a motion vector (MV) of a current block of a current picture in Inter, or Merge, or Skip mode, wherein the MV is associated with the current block and a corresponding block of a target reference picture in a given reference list, the apparatus comprising at least one circuit configured for:

for selecting a co-located block corresponding to a co-located picture;

receiving one or more reference motion vectors (MVs) of one or more co-located reference blocks associated with the co-located block;

determining a search set, wherein the search set comprises one or more search MVs associated with said one or more co-located reference blocks;

determining a search order for the search set, wherein the search order starts with searching the search MV corresponding to the given reference list, if the search MV corresponding to the given reference list is not available, the search order then searches the search MV corresponding to a reference list different from the given reference list;

determining the MVP for the current block based on the search set and the search order; and

providing the MVP for the current block,

wherein said one or more co-located reference blocks comprise an inside co-located block at center of the co-located block and an outside co-located block outside the co-located block across from a lower-right corner of the co-located block;

wherein said determining the MVP searches the search MVs associated with the outside co-located block and then the inside co-located block, and the search order for each co-located reference block is from the search MV corresponding to the given reference list, to the search MV corresponding to a reference list different from the given reference list; and

wherein the search order for determining the MVP is from the search MV corresponding to the given reference list, to the search MV corresponding to a reference list different from the given reference list associated with the outside co-located block; and wherein said determining the MVP further searches the one or more search MVs associated with the inside co-located block if no MVP is found or the MVP found is the same as a previous MVP derived from neighboring blocks of the current block.

18. The apparatus of claim 17 , wherein the co-located picture associated with the co-located block is indicated by a flag, and information associated with the flag is incorporated in a sequence level, a picture level, or a slice level.