Method and apparatus for derivation of spatial motion vector candidate and motion vector prediction candidate
An apparatus and method for deriving a motion vector predictor are disclosed. In video coding systems, the spatial and temporal redundancy is exploited using spatial and temporal prediction to reduce the information to be transmitted or stored. Motion vector prediction has been used to further conserve the bitrate associated with motion vector coding. In a conventional coding system, a motion vector predictor (MVP) is selected from the spatial MVPs and temporal MVP. The spatial MVP according to a conventional approach is based on motion vectors (MVs) of neighboring blocking pointing to a target reference picture in a given reference list. Embodiments according to the present invention perform the MVP search among an extended search set including MVs pointing to other reference pictures in the given reference list or the other reference list and MVs pointing to the target reference picture in the given reference list or the other reference list. Other aspects of the present invention address the search order of the search set and configuration of neighboring blocks.
1. A method of deriving a first motion vector predictor (MVP) and a second MVP for a motion vector (MV) of a current block 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:
receiving first motion vectors (MVs) associated with a first neighboring block group of the current block;
receiving second MVs associated with a second neighboring block group of the current block;
determining first MV attribute search comprising whether a given first MV pointing to the target reference picture in the given reference list, and determining second MV attribute search comprising whether the given first MV pointing to other reference pictures in the given reference list, whether the given first MV pointing to the target reference picture in other reference list, or whether the given first MV pointing to the other reference pictures in the other reference list;
determining third MV attribute search comprising whether a given second MV pointing to the target reference picture in the given reference list, and determining fourth MV attribute search comprising whether the given second MV pointing to the other reference pictures in the given reference list, whether the given second MV pointing to the target reference picture in the other reference list, or whether the given second MV pointing to the other reference pictures in the other reference list;
determining the first MVP for the current block from the first neighboring block group according to a search order, wherein first effective MV is selected as the first MVP, and wherein the search order comprises searching the first MVs for the first effective MV having asserted first MV attribute search firstly; and searching the first MVs for the first effective MV having asserted second MV attribute search firstly when no first MV has the asserted first MV attribute search;
determining the second MVP for the current block from the second neighboring block group according to the search order, wherein second effective MV is selected as the second MVP, and wherein the search order comprises searching the second MVs for the second effective MV having asserted third MV attribute search firstly; and searching the second MVs for the second effective MV having asserted fourth MV attribute search firstly when no second MV has the asserted third MV attribute search;
providing the first MVP for the current block; and
providing the second MVP for the current block.
2. The method of claim 1 , wherein the first neighboring block group comprises a rightmost block on top side, an upper-left corner block and an upper-right corner block of the current block, and wherein search order is from the upper-right corner block to the rightmost block on the top side, and to the upper-left corner block.
3. The method of claim 1 , wherein the second neighboring block group comprises a bottom block on left side and a lower-left corner block of the current block, wherein search order is from the lower-left corner block to the bottom block on the left side.
4. The method of claim 1 , wherein the first MVP is scaled before the first MVP is provided if the first MVP is associated with said at least one of second search MVs pointing to the other reference pictures in the given reference list or the other reference list.
5. The method of claim 1 , wherein the second MVP is scaled before the second MVP is provided if the second MVP is associated with said at least one of fourth search MVs pointing to the other reference pictures in the given reference list or the other reference list.
6. The method of claim 1 , wherein one of the first MV attribute search and the second MV attribute search associated with each of the first MVs are configured as a local search set having a local search order, wherein the search order comprises searching from one local search set to next local search set.
7. The method of claim 1 , wherein, when the second MV attribute search associated with each of the first MVs contains two or more second MV attribute search elements, said two or more second MV attribute search elements are configured as a local search set having a local search order, wherein the search order comprises searching from one local search set to next local search set.
8. The method of claim 1 , wherein one of the third MV attribute search and the fourth MV attribute search MVs associated with each of the second MVs are configured as a local search set having a local search order, wherein the search order comprises searching from one local search set to next local search set.
9. The method of claim 1 , wherein, when the fourth MV attribute search associated with each of the second MVs contains two or more fourth MV attribute search elements, said two or more fourth MV attribute search elements are configured as a local search set having a local search order, wherein the search order comprises searching from one local search set to next local search set.
10. An apparatus of deriving a first motion vector predictor (MVP) and a second MVP for a motion vector (MV) of a current block 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:
means for receiving first motion vectors (MVs) associated with a first neighboring block group of the current block;
means for receiving second MVs associated with a second neighboring block group of the current block;
means for determining first MV attribute search comprising whether a given first MV pointing to the target reference picture in the given reference list, and determining second MV attribute search comprising whether the given first MV pointing to other reference pictures in the given reference list, whether the given first MV pointing to the target reference picture in other reference list, or whether the given first MV pointing to the other reference pictures in the other reference list;
means for determining third MV attribute search comprising whether a given second MV pointing to the target reference picture in the given reference list, and determining fourth MV attribute search comprising whether the given second MV pointing to other reference pictures in the given reference list, whether the given second MV pointing to the target reference picture in other reference list, or whether the given second MV pointing to the other reference pictures in the other reference list;
means for determining the first MVP for the current block from the first neighboring block group according to a search order, wherein first effective MV is selected as the first MVP, and wherein the search order comprises searching the first MVs for the first effective MV having asserted first MV attribute search firstly; and searching the first MVs for the first effective MV having asserted second MV attribute search firstly when no first MV has the asserted first MV attribute search;
means for determining the second MVP for the current block from the second neighboring block group according to the search order, wherein second effective MV is selected as the second MVP, and wherein the search order comprises searching the second MVs for second effective MV having asserted third MV attribute search firstly; and searching the second MVs for the second effective MV having asserted fourth MV attribute search firstly when no second MV has the asserted third MV attribute search;
means for providing the first MVP for the current block; and
means for providing the second MVP for the current block.
11. The apparatus of claim 10 , wherein the first neighboring block group comprises a rightmost block on top side, an upper-left corner block and an upper-right corner block of the current block, and wherein search order is from the upper-right corner block to the rightmost block on the top side, and to the upper-left corner block.
12. The apparatus of claim 10 , wherein the second neighboring block group comprises a bottom block on left side and a lower-left corner block of the current block, wherein search order is from the lower-left corner block to the bottom block on the left side.
13. The apparatus of claim 10 , wherein the first MVP is scaled before the first MVP is provided if the first MVP is associated with said at least one of second search MVs pointing to the other reference pictures in the given reference list or the other reference list.