US 12,470,718 B2
Method for encoding/decoding image using bi-directional optical flow prediction
Ha Hyun Lee, Seoul (KR); Jung Won Kang, Daejeon (KR); Hyun Suk Ko, Daejeon (KR); Sung Chang Lim, Daejeon (KR); Jin Ho Lee, Daejeon (KR); Dong San Jun, Daejeon (KR); and Hui Yong Kim, Daejeon (KR)
Assigned to INTELLECTUAL DISCOVERY CO., LTD, Seoul (KR)
Appl. No. 16/650,591
Filed by INTELLECTUAL DISCOVERY CO., LTD., Seoul (KR)
PCT Filed Sep. 28, 2018, PCT No. PCT/KR2018/011487
§ 371(c)(1), (2) Date Mar. 25, 2020,
PCT Pub. No. WO2019/066523, PCT Pub. Date Apr. 4, 2019.
Claims priority of application No. 10-2017-0128129 (KR), filed on Sep. 29, 2017; application No. 10-2018-0072370 (KR), filed on Jun. 22, 2018; and application No. 10-2018-0113942 (KR), filed on Sep. 21, 2018.
Prior Publication US 2020/0236362 A1, Jul. 23, 2020
Int. Cl. H04N 19/137 (2014.01); H04N 19/117 (2014.01); H04N 19/119 (2014.01); H04N 19/159 (2014.01); H04N 19/176 (2014.01); H04N 19/186 (2014.01); H04N 19/513 (2014.01); H04N 19/52 (2014.01); H04N 19/573 (2014.01)
CPC H04N 19/137 (2014.11) [H04N 19/117 (2014.11); H04N 19/119 (2014.11); H04N 19/159 (2014.11); H04N 19/176 (2014.11); H04N 19/186 (2014.11); H04N 19/513 (2014.11); H04N 19/52 (2014.11); H04N 19/521 (2014.11); H04N 19/573 (2014.11)] 3 Claims
OG exemplary drawing
 
1. A method of decoding an image, the method comprising:
dividing a current block to acquire a subblock of the current block;
determining whether to perform a subblock based BI-DIRECTIONAL OPTICAL FLOW (BIO) prediction on the subblock;
deriving a first direction prediction sample and a second direction prediction sample of the subblock;
deriving a BIO offset of the subblock;
generating a final prediction sample of the subblock block using the first direction prediction sample, the second direction prediction sample and the BIO offset; and
generating a reconstructed sample of the current block based on the final prediction sample,
wherein whether to perform the subblock based BIO prediction determines based on a result of comparing a threshold value and a difference between the first direction prediction sample and the second direction prediction sample,
wherein the threshold value is set using on a size of the current block,
wherein the deriving a BIO offset comprising:
deriving a gradient using neighboring samples;
deriving a motion refining vector; and
deriving the BIO offset based on the gradient and the motion refining vector,
wherein the gradient is, when a position of the neighboring sample is a subpixel position, derived by rounding to an integer pixel position close to the subpixel position.