How we score video quality — and what VMAF actually measures

A single "quality up +30" number usually mixes two jobs: repair (cleaner at the same size) and upscale (more pixels). Stretching 480p to 4K can print a pretty delta even when blocks were never cleaned. After a preview, KwaFlux quality detection reports three parts — source, same-resolution repair, and resolution delivery — so the easy score cannot hide the hard work. Pair this with the AI Video Enhancer or AI Color Enhance.

Tool A blows a soft 480p clip to 4K and barely denoises. Tool B outputs 1080p but actually removes blocks. A before/after total often crowns A, because resolution is the cheapest way to look improved. Six months later you are watching B's work. Resolution is easy to score. Repair is the work. One number systematically rewards the first and hides the second.

1. Source quality — sharpness, cleanliness, color, motion on the original. Where did you start, and how much headroom is left?
2. Same-resolution repair — compare processed vs original at one size. Denoise, deblock, and texture fidelity without the canvas jump
3. Resolution delivery — the upscale gain, gated by repair quality. A dirty frame grown larger is a larger dirty frame

The delivery total is repair content plus that gated resolution term. All three stay visible. We describe the idea, not internal field names.

• VMAF (Netflix, open source) answers "how like the reference is this frame?" — not "how much better did we make it?"
• High VMAF = close to the reference style. Low VMAF = a large rewrite, which might be an improvement or over-cooking. Eyes decide
• If a vendor shouts "VMAF up X%", ask what the reference was. If it is a naive stretch of the bad original, a high score can mean "we changed little"

Inside KwaFlux, VMAF is a fidelity hint that flags a heavy rewrite for a visual check. It is not advertised as a quality-up proof. Detection is a navigation aid across settings. Download and settle the 1s/3s/5s preview yourself — no account for those previews; export is on pricing.