	US 12,108,057 B2
	Prediction image generation device, moving image decoding device, moving image encoding device, and prediction image generation method
Frank Bossen, Vancouver, WA (US); Eiichi Sasaki, Sakai (JP); Yukinobu Yasugi, Sakai (JP); and Tomohiro Ikai, Sakai (JP)
Assigned to SHARP KABUSHIKI KAISHA, Osaka (JP); and FG Innovation Company Limited, Tuen Mun (HK)
Appl. No. 17/419,416
Filed by SHARP KABUSHIKI KAISHA, Sakai (JP); and FG Innovation Company Limited, Tuen Mun (HK)
PCT Filed Dec. 26, 2019, PCT No. PCT/JP2019/051080 § 371(c)(1), (2) Date Jun. 29, 2021, PCT Pub. No. WO2020/141599, PCT Pub. Date Jul. 9, 2020.
Claims priority of provisional application 62/787,646, filed on Jan. 2, 2019.
Prior Publication US 2021/0392344 A1, Dec. 16, 2021
Int. Cl. H04N 19/186 (2014.01); H04N 19/105 (2014.01); H04N 19/174 (2014.01); H04N 19/96 (2014.01)

CPC H04N 19/186 (2014.11) [H04N 19/105 (2014.11); H04N 19/174 (2014.11); H04N 19/96 (2014.11)]

7 Claims

1. A moving image decoding device for deriving a prediction image of a chrominance image by using a luminance image, the moving image decoding device comprising:

one or more processors; and

one or more computer-readable media coupled to the one or more processors and storing one or more computer-executable instructions that, when executed by at least one of the one or more processors, cause the moving image decoding device to:

derive a first luminance value on the luminance image corresponding to a first position;

derive a first chrominance value on the chrominance image corresponding to the first position;

derive a second luminance value on the luminance image corresponding to a second position;

derive a second chrominance value on the chrominance image corresponding to the second position;

derive a first difference value that indicates a difference between the first luminance value and the second luminance value;

derive a second difference value that indicates a difference between the first chrominance value and the second chrominance value;

derive a shift value for a shift operation, a first parameter, and a second parameter by using the first difference value and the second difference value;

set the shift value to a first threshold based on a comparison between the first threshold and a third value, the third value beingcalculated by adding a first specified value to a first value, derived by using the first difference value, and then subtracting a second value, derived by using the second difference value, from a result of the addition, wherein:

the first parameter is set to a value resulting from multiplying a second specified value by a sign of the first parameter if the third value is less than the first threshold, and

the second specified value is 15;

derive the prediction image by using the first parameter, the second parameter, and the shift value; and

derive the second parameter by using the second luminance value, the second chrominance value, the first parameter, and the shift value, and according to the formula:

b=C_Y_MIN−((a*Y_MIN)>>shiftA)

wherein:

C_Y_MIN is the second chrominance value, a is the first parameter, Y_MIN is the second luminance value, and shiftA is the shift value.