What is VMAF and How to Use It for Video Quality

What is VMAF?

VMAF — Video Multi-Method Assessment Fusion — is a video quality metric developed by Netflix to predict how good a video looks to actual human viewers. Instead of relying on a single formula, it fuses several quality measures together using a model trained on real human opinion scores. The result is a number that tracks perceived quality far better than older metrics on their own.

How to read a VMAF score

VMAF is reported on a 0–100 scale, where higher is better:

• 95–100 — visually indistinguishable from the source for most viewers.
• 80–95 — good quality; minor artefacts only noticeable on close inspection.
• 60–80 — acceptable but visibly degraded.
• Below 60 — clearly degraded quality.

Roughly, every ~6 VMAF points corresponds to a noticeable step in perceived quality. It’s a “full-reference” metric, meaning it compares an encoded video against the original source.

VMAF vs PSNR vs SSIM

• PSNR measures raw pixel error. Simple and fast, but it doesn’t match human perception well — two videos with the same PSNR can look very different.
• SSIM measures structural similarity (contrast, luminance, structure). Much closer to perception than PSNR.
• VMAF goes furthest: it’s trained on human opinion scores and fuses multiple measures, so it’s the best single predictor of perceived quality — which is why it’s the industry standard for encoding decisions.

Use PSNR/SSIM for quick checks; use VMAF when you care about how the video actually looks to viewers.

How to get a VMAF score for your videos

You don’t need a complex toolchain. DiffALL computes VMAF (alongside SSIM and PSNR) when you compare two videos:

1. Upload the original and the encoded/compressed version.
2. DiffALL analyses the frames and reports an overall VMAF score, plus per-second SSIM and a difference heatmap.
3. Use the score to decide whether your encoding settings preserved enough quality — or where it dropped.

Common use cases

• Encoding decisions — compare bitrate or codec settings and pick the one that keeps VMAF high.
• Transcoding QA — confirm a converted video didn’t lose perceptible quality.
• Streaming optimisation — balance file size against perceived quality with a number you can trust.

Try it now

Want a VMAF score for your own footage? Upload the original and the encoded version and let DiffALL measure exactly how much quality you kept.