@nuintari @fuomag9 @0xabad1dea Anime fansubs have been known to process video to improve quality (often by undoing broken processing done on the official version).

Things like realizing that the original is a 720p master upscaled to 1080p 4:2:0 with a crappy bilinear filter, and undoing the filter to precisely reconstruct a 720p luma channel with ~540p chroma content, then encoding it as 720p 4:4:4 to allow higher quality upscaling on playback (since most decent video players do better than bilinear) and a lower file size.