Cross-component linear model prediction image generation apparatus, video decoding apparatus, video coding apparatus, and prediction image generation method

A prediction image generation apparatus for generating a prediction image based on an intra prediction mode, the prediction image generation apparatus comprising:

• Cross-Component Linear Model (CCLM) prediction parameter circuitry that derives:
• (i) a difference value for a luminance component, which is a difference between a first value and a second value;
• (ii) a difference value for a chrominance component, which is a difference between a third value and a fourth value;
• (iii) a CCLM prediction parameter by using the difference value for the luminance component and the difference value for the chrominance component;
• and
• a CCLM prediction filter that derives the prediction image by using the CCLM prediction parameter, wherein
• the CCLM prediction parameter circuitry derives:
• (i) a first logarithmic value by using the difference value for the luminance component;
• (ii) a second logarithmic value by using an absolute value of the difference value for the chrominance component;
• and
• (iii) a first shift value by using the first logarithmic value and the second logarithmic value;
• the CCLM prediction filter derives the prediction image by using the first shift value;
• the CCLM prediction parameter is derived by right shifting a sixth value by the second logarithmic value;
• and
• the sixth value is a value obtained by using a fifth value and the difference value for the chrominance component, the fifth value being a value in a reference table defined by using the difference value for the luminance component.