Inter prediction mode-based image processing method and apparatus therefor
Disclosed are an inter prediction mode-based image processing method and an apparatus therefor. Particularly, a method for processing an image on the basis of inter prediction may comprise the steps of: determining whether a motion vector scale adaptation is applied to a block; up-scaling a down-scaled MVD (Motion Vector Difference) when the motion vector scale adaptation is applied to the block; deriving a MV (Motion Vector) for the block, using the up-scaled MVD and a MVP (Motion Vector Predictor); and generating a predictive block of the block, using the derived MV.
1. A method of processing an image based on inter-prediction by an apparatus, comprising steps of:
obtaining a motion vector difference (MVD) for a current block;
obtaining a flag indicating a resolution of the MVD;
rounding, based on the flag, a motion vector predictor (MVP) obtained from a neighbor block of the current block;
up-scaling the MVD based on the flag;
deriving a motion vector (MV) for the current block based on the up-scaled MVD and the rounded MVP; and
generating a prediction block of the current block based on the derived MV.
2. The method of claim 1 , wherein the MVD is generated by applying at least one of round, floor, and ceiling operations to a value obtained by subtracting the MVP from the MV.
3. The method of claim 1 , wherein, if the flag is equal to a first value, a round function is applied to the MVP and the MVD is multiplied by 4.
4. The method of claim 1 , wherein the flag is parsed only when the MVD is not 0.
5. The method of claim 1 , wherein the MVD is grouped in units of intervals and binary-encoded.
6. The method of claim 5 , wherein the MVD value is encoded as a start value of an interval to which the MVD belongs and indication information for indicating the MVD within the interval.
7. The method of claim 6 , wherein the start value is down-scaled at a ratio of a size of the interval and transmitted.
8. The method of claim 7 , wherein the size of the interval is predetermined or transmitted from an encoder.
9. The method of claim 5 , wherein the MVD is grouped in units of intervals and encoded only when the MVD is 2 or more.
10. The method of claim 5 , wherein a size of the interval is set to a square number of 2.
11. An apparatus for processing an image based on inter-prediction, comprising:
a processor configured to:
obtain a motion vector difference (MVD) for a current block;
obtain a flag indicating a resolution of the MVD;
round, based on the flag, a motion vector predictor (MVP) obtained from a neighbor block of the current block;
up-scale the MVD based on the flag;
derive a motion vector (MV) for the current block based on the up-scaled MVD and the rounded MVP; and
generate a prediction block of the current block based on the derived MV.