CRF（质量参数）CRF
交付 · Delivery
CRF 是 x264 / x265 的恒定质量参数——数值越小质量越高、体积越大；设了它就不用再设码率。
- 怎么选（H.264 / H.265 通用）：18 接近无损，母版留档；23 日常交付；28+ 暗部和渐变开始出块。
- 和 -preset 配合：preset slow 慢一点，换同样质量下更小的体积（文件小的是体积，不是画质更好）。
- 对比试验：同一段素材分别用 crf 18 / 23 / 28 导出，看体积差多少、色带从哪一档开始出现。
CRF is the constant-quality dial of x264 / x265 — lower means better quality and bigger files; set it and you skip the bitrate.
- How to choose (H.264 / H.265 alike): 18 near-lossless, for archive masters; 23 everyday delivery; 28+ blocks start appearing in shadows and gradients.
- Paired with -preset: preset slow takes longer for a smaller file at the same quality — it shrinks the size, it does not raise the quality.
- Try it yourself: export one clip at crf 18 / 23 / 28 and see how the size moves and where the banding starts.