After a month, there are so many problem, with broken monitor all of sudden, and had to purchase new one, now I so broke, however I still continue working on this project!
I just updated IFME into latest version of x265 (1.0+139-a5998df9b12e) including dithering support, this allow colour loss undetected by normal eye, making it look smooth, useful when down sample to 8bit.