Video signal processing method and apparatus using adaptive motion vector resolution

1. An apparatus for decoding a video signal, the apparatus comprising

a processor,

wherein the processor is configured to:

configure a Motion Vector Prediction (MVP) candidate list for motion compensation of a current block through one of a first method and a second method,

acquire a motion vector predictor of the current block, based on the configured MVP candidate list,

acquire a motion vector differential value indicating a difference between a motion vector of the current block and the motion vector predictor,

acquire a first value of an indicator indicating at least one of a first resolution of the motion vector differential value of the current block and a second resolution of the motion vector differential value of the current block,

wherein the first resolution is one of a plurality of available resolutions included in a first resolution set and the second resolution is one of a plurality of available resolutions included in a second resolution set,

wherein which one of the first resolution set and the second resolution set is used is determined based on at least one of the first method and the second method,

wherein both the first resolution set and the second resolution set include a resolution in unit of 1 sample,

wherein the resolution in unit of 1 sample included in the first resolution set and the resolution in unit of 1 sample included in the second resolution set are indicated by different values of the indicator,

modify the motion vector differential value, based on a resolution of the motion vector differential value of the current block,

wherein the resolution of the motion vector differential value is the first resolution or the second resolution,

wherein the resolution of the motion vector differential value is determined based on at least one of the first method and the second method,

acquire the motion vector of the current block, based on the motion vector predictor and the modified motion vector differential value, and

reconstruct the current block, based on the acquired motion vector.

2. The apparatus of claim 1 ,

wherein the second resolution set includes at least one of available resolutions other than the plurality of available resolutions included in the first resolution set.

3. The apparatus of claim 2 , wherein, when the MVP candidate list is configured using the first method based on an affine model, the resolution of the motion vector differential value is acquired from the first resolution set, and when the MVP candidate list is configured using the second method, which is not based on the affine model, the resolution of the motion vector differential value is acquired from the second resolution set.

4. The apparatus of claim 3 , wherein a largest first available resolution among the plurality of available resolutions included in the first resolution set is smaller than a largest second available resolution among the plurality of available resolutions included in the second resolution set.

5. The apparatus of claim 4 , wherein the largest first available resolution is the resolution in units of 1 sample, and

the largest second available resolution is a resolution in units of 4 samples.

6. The apparatus of claim 2 , wherein a number of available resolutions included in the first resolution set and a number of available resolutions included in the second resolution set are different from each other.

7. The apparatus of claim 6 , wherein the number of available resolutions included in the first resolution set and the number of available resolutions included in the second resolution set are determined based on a Picture Order Count (POC) of a reference picture for motion compensation of the current block.

8. The apparatus of claim 7 , wherein, when the Picture Order Count (POC) of the reference picture for motion compensation of the current block is equal to a POC of a current picture including the current block, the resolution of the motion vector differential value of the current block is acquired from the first resolution set,

when the POC of the reference picture for motion compensation of the current block is not equal to the POC of the current picture including the current block, the resolution of the motion vector differential value of the current block is acquired from the second resolution set, and

the first resolution set is configured available resolutions except for a smallest available resolution and the second smallest available resolution among the available resolutions included in the second resolution set.

9. The apparatus of claim 1 , wherein, when the MVP candidate list is configured using the first method, the first value indicates a first available resolution, which is one of the plurality of available resolutions included in the first resolution set,

when the MVP candidate list is configured using the second method, the first value indicates a second available resolution, which is one of the plurality of available resolutions included in the second resolution set, and

the first available resolution and the second available resolution are different from each other.

10. The apparatus of claim 1 , wherein the indicator is expressed by variable-length bits, and

the first value is one of a plurality of values expressed by the variable-length bits.

11. An apparatus for encoding a video signal, the apparatus comprising

a processor,

wherein the processor is configured to

obtain a bitstream to be decoded by a decoder using a decoding method,

wherein the decoding method comprising:

configuring a Motion Vector Prediction (MVP) candidate list for motion compensation of a current block through one of a first method and a second method,

acquiring a motion vector predictor of the current block, based on the configured MVP candidate list,

acquiring a motion vector differential value indicating a difference between a motion vector of the current block and the motion vector predictor,

acquire a first value of an indicator indicating at least one of a first resolution of the motion vector differential value of the current block and a second resolution of the motion vector differential value of the current block,

wherein the first resolution is one of a plurality of available resolutions included in a first resolution set and the second resolution is one of a plurality of available resolutions included in a second resolution set,

wherein which one of the first resolution set and the second resolution set is used is determined based on at least one of the first method and the second method,

wherein both the first resolution set and the second resolution set include a resolution in unit of 1 sample,

wherein the resolution in unit of 1 sample included in the first resolution set and the resolution in unit of 1 sample included in the second resolution set are indicated by different values of the indicator,

modifying the motion vector differential value, based on a resolution of the motion vector differential value of the current block,

wherein the resolution of the motion vector differential value is the first resolution or the second resolution,

wherein the resolution of the motion vector differential value is determined based on at least one of the first method and the second method,

acquiring the motion vector of the current block, based on the motion vector predictor and the modified motion vector differential value, and

reconstructing the current block, based on the acquired motion vector.

12. The apparatus of claim 11 ,

wherein the second resolution set includes at least one of available resolutions other than the plurality of available resolutions included in the first resolution set.

13. The apparatus of claim 12 , wherein a largest first available resolution among the plurality of available resolutions included in the first resolution set is smaller than a largest second available resolution among the plurality of available resolutions included in the second resolution set.

14. The apparatus of claim 13 ,

wherein the largest first available resolution is the resolution in units of 1 sample, and the largest second available resolution is a resolution in units of 4 samples.

15. The apparatus of claim 14 , wherein the indicator is expressed by variable-length bits, and

the first value is one of a plurality of values expressed by the variable-length bits.

16. The apparatus of claim 15 , wherein a second value different from the first value of the indicator is a value expressed by shortest length bits among the plurality of values,

when the MVP candidate list is configured using the second method, the second value indicates a smallest available resolution among a plurality of available resolution sets included in the second resolution set, and

when the MVP candidate list is configured using the first method, the second value indicates an available resolution other than a smallest available resolution among a plurality of available resolution sets included in the first resolution set.

17. A non-transitory computer-readable medium storing a bitstream, the bitstream being decoded by a decoding method,

wherein the decoding method, comprising:

configuring a Motion Vector Prediction (MVP) candidate list for motion compensation of a current block through one of a first method and a second method,

acquiring a motion vector predictor of the current block, based on the configured MVP candidate list,

acquiring a motion vector differential value indicating a difference between a motion vector of the current block and the motion vector predictor,

acquire a first value of an indicator indicating at least one of a first resolution of the motion vector differential value of the current block and a second resolution of the motion vector differential value of the current block,

wherein the first resolution is one of a plurality of available resolutions included in a first resolution set and the second resolution is one of a plurality of available resolutions included in a second resolution set,

wherein which one of the first resolution set and the second resolution set is used is determined based on at least one of the first method and the second method,

wherein both the first resolution set and the second resolution set included a resolution in unit of 1 sample,

wherein the resolution in unit of 1 sample include in the first resolution set and the resolution in unit of 1 sample included in the second resolution set are indicated by different values of the indicator,

modifying the motion vector differential value, based on a resolution of the motion vector differential value of the current block,

wherein the resolution of the motion vector differential value is the first resolution or the second resolution,

wherein the resolution of the motion vector differential value is determined based on at least one of the first method and the second method,

acquiring the motion vector of the current block, based on the motion vector predictor and the modified motion vector differential value, and

reconstructing the current block, based on the acquired motion vector.