Method of adaptive motion vector resolution for video coding
A method of MVP (motion vector prediction) for video coding with adaptive motion vector resolution is disclosed. According to the present invention, the MVP coding is applied to the current MV or the current MV is stored depending on the current MV resolution, the reference MV resolution, or both the current MV resolution and the reference MV resolution. In one embodiment, when the current MV resolution corresponds to integer pixel resolution, MVP coding is then applied to the current MV using a modified temporal MV as a motion vector predictor for the current MV, where the modified temporal MV is generated by right-shifting the temporal MV. In another embodiment, when the current MV resolution corresponds to integer pixel resolution, the current MV is left-shifted before it is stored in a memory.
1. A method of MVP (motion vector prediction) for video data, the method comprising:
receiving input data associated with a current MV (motion vector) for a current block in a current slice;
determining current MV resolution for the current MV, reference MV resolution for a reference MV associated with a reference block in a reference picture, or both the current MV resolution and the reference MV resolution; and
applying MVP coding to the current MV or storing the current MV depending on the current MV resolution, the reference MV resolution, or both the current MV resolution and the reference MV resolution, wherein when the reference MV associated with the reference block in the reference picture corresponds to a temporal MV associated with a temporal reference block in the reference picture and the current MV resolution corresponds to integer pixel resolution, said applying MVP coding to the current MV uses a modified temporal MV as a motion vector predictor for the current MV, wherein the modified temporal MV is generated by right-shifting the temporal MV, wherein when a shift operation is applied to the current MV or the temporal MV due to the current MV resolution or the reference MV resolution respectively, the current MV shifted or the temporal MV shifted after applying MVP coding is constrained to a valid range.
2. The method of claim 1 , wherein when the current MV resolution corresponds to integer pixel resolution, the current MV is left-shifted before it is stored in a memory.
3. The method of claim 1 , wherein the current MV stored in a memory is right-shifted before it is used as a motion vector predictor for another block in a current picture containing the current slice.
4. The method of claim 1 , wherein when the current MV resolution corresponds to integer pixel resolution, the current MV is left-shifted before it is used in determination of boundary strength used for a deblocking process.
5. The method of claim 1 , wherein when the current MV resolution corresponds to non-integer pixel resolution and the reference MV resolution corresponds to integer pixel resolution, said applying MVP coding to the current MV uses a modified temporal MV as a motion vector predictor for the current MV, wherein the modified temporal MV is generated by left-shifting the temporal MV.
6. The method of claim 1 , wherein when the current MV resolution is different from the reference MV resolution, said applying MVP coding to the current MV disables the MVP coding for the current block.
7. The method of claim 1 , wherein when the current MV resolution is different from the reference MV resolution, said applying MVP coding to the current MV disregards the reference picture for the MVP coding of the current block.
8. The method of claim 1 , wherein the current MV has different ranges for different current MV resolutions or the temporal MV has different ranges for different reference MV resolutions.
9. The method of claim 1 , wherein the current MV resolution is indicated by a MV resolution flag in a slice header and all blocks within a corresponding slice share the MV resolution flag.
10. The method of claim 1 , wherein the current MV resolution is indicated by a MV resolution flag in a sequence level and all blocks within a corresponding sequence share the MV resolution flag.
11. An apparatus of MVP (motion vector prediction) for video data, comprising one or more electronic circuits arranged to:
receive input data associated with a current MV (motion vector) for a current block in a current slice;
determine current MV resolution for the current MV, reference MV resolution for a reference MV associated with a reference block in a reference picture, or both the current MV resolution and the reference MV resolution; and
apply MVP coding to the current MV or store the current MV depending on the current MV resolution, the reference MV resolution, or both the current MV resolution and the reference MV resolution, wherein when the reference MV associated with the reference block in the reference picture corresponds to a temporal MV associated with a temporal reference block in the reference picture and the current MV resolution corresponds to integer pixel resolution, said applying MVP coding to the current MV uses a modified temporal MV as a motion vector predictor for the current MV, wherein the modified temporal MV is generated by right-shifting the temporal MV, wherein when a shift operation is applied to the current MV or the temporal MV due to the current MV resolution or the reference MV resolution respectively, the current MV shifted or the temporal MV shifted after applying MVP coding is constrained to a valid range.