Constant REFINE_FINER 

pub const REFINE_FINER: u32 = 6;

Quality index steps finer than the paint-over one x264 codes a refined block at, so the block comes to what the region’s own cleanup reaches: one predicted frame at the paint-over quantizer left 1080p text at 44.6 dB, where the cleanup’s key frame, at x264’s intra offset, reached 49.1; six steps finer reached 49.4. Each encoder that refines says its own (FrameEncoder::refines).