Method for storing motion information and method for inducing temporal motion vector predictor using same
A motion information storing method and a TMVP deriving method using the motion information storing method are provided. The motion information storing method includes a step of determining a representative block out of blocks of a motion data storage unit in a co-located picture with a current picture and a step of storing motion information of the representative block as motion information of the motion data storage unit, wherein the motion information of the representative block is used as motion information of the blocks included in the motion data storage unit.
1. A method for inter prediction, by a decoding apparatus, comprising:
determining a positioning pixel for a temporal motion vector predictor (TMVP) of a current block of a current picture;
deriving a co-located prediction block (colPb) in a reference picture based on the positioning pixel;
deriving the temporal motion vector predictor (TMVP) of the current block of a current picture based on a motion vector of the co-located prediction block (colPb) in the reference picture; and
performing inter prediction for the current block based on the TMVP derived based on the motion vector of the colPb in the reference picture,
wherein the co-located prediction block (colPb) is a prediction block covering a modified location that is determined based on a location of the positioning pixel, and
wherein the positioning pixel is determined as a pixel at a right-bottom side among four pixels located at the center of a co-located block in the reference picture, wherein the co-located block is a block corresponding to the current block and located in the reference picture.
2. The method of claim 1 , wherein the modified location is specified by ((xPCtr>>4)<<4, (yCtr>>4)<<4)), wherein (xPCtr, yPCtr) is the location of the positioning pixel.
3. The method of claim 2 , wherein the modified location is a location at a top left corner in a motion data storage unit area including the positioning pixel.
4. The method of claim 3 , wherein the motion vector of the co-located prediction block covering the modified location is used as a representative motion vector of prediction blocks in the motion data storage unit area.
5. The method of claim 4 , wherein a size of the motion data storage unit area is 16×16 samples.
6. The method of claim 2 , wherein the location of the positioning pixel is specified by (xP+(nPSW>>1), yP+(nPSH>>1)), wherein (xP, yP) is a location of a top left sample of the current block, nPSW and nPSH are width and height of the current block respectively.
7. The method of claim 6 , wherein the pixel at the right-bottom side among four pixels located at the center of the co-located block is determined as the positioning pixel when a bottom of the co-located block is a boundary of a largest coding unit.
8. The method of claim 6 , wherein the pixel at the right-bottom side among four pixels located at the center of the co-located block is determined as the positioning pixel when a pixel adjacent to a right-bottom corner of the co-located block is out of a boundary of a largest coding unit to which the co-located block belongs.
9. The method of claim 6 , wherein availability information is signaled, which indicates whether the temporal motion vector predictor can be used for the current picture, and
wherein the temporal motion vector predictor derived when the availability information does not indicate that temporal motion vector predictor is not used for the current picture.
10. The method of claim 1 , wherein the modified location is a location at a top left corner in a specific square region including the positioning pixel.
11. A decoding apparatus for decoding a video, comprising:
a prediction module for determining a positioning pixel for a temporal motion vector predictor (TMVP) of a current block of a current picture, for deriving a co-located prediction block (colPb) in a reference picture based on the positioning pixel, for deriving the temporal motion vector predictor (TMVP) of the current block of a current picture based on a motion vector of the co-located prediction block (colPb) in the reference picture, and for performing inter prediction for the current block based on the TMVP derived based on the motion vector of the colPb in the reference picture; and
a memory for storing the motion vector of the co-located prediction block (colPb) in the reference picture,
wherein the co-located prediction block (colPb) is a prediction block covering a modified location that is determined based on a location of the positioning pixel, and
wherein the positioning pixel is determined as a pixel at a right-bottom side among four pixels located at the center of a co-located block in the reference picture, wherein the co-located block is a block corresponding to the current block and located in the reference picture.
12. The apparatus of claim 11 , wherein the modified location is specified by ((xPCtr>>4)<<4, (yCtr>>4)<<4)), wherein (xPCtr, yPCtr) is the location of the positioning pixel.
13. The apparatus of claim 12 , wherein the modified location is a location at a top left corner in a motion data storage unit area including the positioning pixel.
14. The apparatus of claim 13 , wherein the motion vector of the co-located prediction block covering the modified location is used as a representative motion vector of prediction blocks in the motion data storage unit area.
15. The apparatus of claim 14 , wherein a size of the motion data storage unit area is 16×16 samples.
16. The apparatus of claim 12 , wherein the location of the positioning pixel is specified by (xP+(nPSW>>1), yP+(nPSH>>1)), wherein (xP, yP) is a location of a top left sample of the current block, nPSW and nPSH are width and height of the current block respectively.
17. The apparatus of claim 16 , wherein the pixel at the right-bottom side among four pixels located at the center of the co-located block is determined as the positioning pixel when a bottom of the co-located block is a boundary of a largest coding unit.
18. The apparatus of claim 16 , wherein the pixel at the right-bottom side among four pixels located at the center of the co-located block is determined as the positioning pixel when a pixel adjacent to a right-bottom corner of the co-located block is out of a boundary of a largest coding unit to which the co-located block belongs.
19. The apparatus of claim 16 , wherein availability information is signaled, which indicates whether the temporal motion vector predictor can be used for the current picture, and
wherein the temporal motion vector predictor derived when the availability information does not indicate that temporal motion vector predictor is not used for the current picture.
20. The apparatus of claim 11 , wherein the modified location is a location at a top left corner in a specific square region including the positioning pixel.