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 an offset is added to the temporal MV before the temporal MV is right-shifted to generate the modified temporal MV.
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 2 , wherein the current MV stored in the 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 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 is clipped to a valid range.
9. 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.
10. 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.
11. 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.
12. A method of deblocking for reconstructed video data, the method comprising:
receiving input data associated with a current reconstructed block in a current slice;
determining MV (motion vector) resolution associated with the current slice;
determining a current MV associated with the current reconstructed block;
determining a neighboring MV associated with a neighboring reconstructed block in the current slice and adjacent to a block boundary of the current reconstructed block; and
deblocking the block boundary depending on the MV resolution, wherein when the MV resolution corresponds to integer resolution, the current MV and the neighboring MV are left-shifted by 2 to become a shifted current MV and a shifted neighboring MV, and the shifted current MV and the shifted neighboring MV are included in determination of boundary strength used for said deblocking.
13. The method of claim 12 , wherein when the MV resolution corresponds to integer resolution, a first absolution difference in a vertical component between the current MV and the neighboring MV and a second absolution difference in a horizontal component between the current MV and the neighboring MV are compared to a threshold value of one among a choice of one and four to determine boundary strength used for said deblocking.