The original source has fair quality, with sharp pictures and many textural details. We can see Xebec spent effort in creating the CG drawings, dark scenes and a 24fps ED. Unfortunately, the sharp edges have significant aliasing in both luma and chroma planes, making non-destructive anti-aliasing challenging. The strong and fine film grain has also made it difficult for x265 to encode the anime at an acceptable bitrate.
To tackle the problems, we adopted a hybrid anti-aliasing approach combining traditional and non-conventional techniques, and operated under the YUV444 color space. The approach repaired most aliasing and without damaging the sharp colored edges. Meanwhile, a tailored grain processing procedure was formulated, which achieved a good balance between picture preservation and bitrate saving.