Method and apparatus for deriving motion vector
Provided is an image decoding method performed by a decoding apparatus including deriving a temporary reference motion vector for a current block included in a current picture, deriving a reference motion vector for the current block by applying clipping to the temporary reference motion vector, deriving a motion vector for the current block based on the reference motion vector, deriving a predicted block for the current block based on the motion vector for the current block, and generating a reconstructed picture for the current picture based on the predicted block for the current block, wherein a number of bits of a binary code representing the reference motion vector is less than a number of bits of a binary code representing the temporary reference motion vector.
1. An image decoding method performed by a decoding apparatus, the image decoding method comprising:
obtaining image information comprising prediction mode information representing a prediction mode of a current block;
deriving the prediction mode of the current block as an inter prediction mode based on the prediction mode information;
deriving a temporary reference motion vector for the current block included in a current picture;
deriving a reference motion vector for the current block by applying clipping to the temporary reference motion vector;
deriving a motion vector for the current block based on the reference motion vector; and
deriving prediction samples for the current block based on the motion vector for the current block;
wherein the reference motion vector is derived based on an equation below,
mv
=
Clip
3
(
-
2
^
17
,
2
^
17
-
1
,
mv
’
)
,
and
wherein the mv′ in the equation represents the temporary reference motion vector, and the mv represents the reference motion vector.
2. An image encoding method performed by an encoding apparatus, the image encoding method comprising:
deriving a prediction mode of a current block as an inter prediction mode;
deriving a temporary reference motion vector for the current block included in a current picture;
deriving a reference motion vector for the current block by applying clipping to the temporary reference motion vector;
deriving a motion vector for the current block based on the reference motion vector;
deriving prediction samples for the current block based on the motion vector for the current block; and
encoding image information including prediction mode information representing the prediction mode of the current block,
wherein the reference motion vector is derived based on an equation below,
mv
=
Clip
3
(
-
2
^
17
,
2
^
17
-
1
,
mv
’
)
,
and
wherein the mv′ in the equation represents the temporary reference motion vector, and the mv represents the reference motion vector.
3. A transmission method of data for an image, the transmission method comprising:
obtaining a bitstream for the image, wherein the bitstream is generated based on deriving a prediction mode of a current block as an inter prediction mode, deriving a temporary reference motion vector for the current block included in a current picture, deriving a reference motion vector for the current block by applying clipping to the temporary reference motion vector, deriving a motion vector for the current block based on the reference motion vector, deriving prediction samples for the current block based on the motion vector for the current block and encoding image information including prediction mode information representing the prediction mode of the current block; and
transmitting the data comprising the bitstream,
wherein the reference motion vector is derived based on an equation below,
mv
=
Clip
3
(
-
2
^
17
,
2
^
17
-
1
,
mv
’
)
,
and
wherein the mv′ in the equation represents the temporary reference motion vector, and the mv represents the reference motion vector.