SlimeCodec NormMAP — measurement ledger and verification record
Development history, measurement procedure and primary sources, split out from the product page (NormH.264). Every number here is checked against the raw benchmark logs, and anything we have not verified is stated as not verified. Last updated: 2026-07-26.
(1) Reduction against the source file (the −74.3% on the product page): how much smaller the output is than the input. This depends heavily on the input bitrate — a bloated master shrinks far more. It maps directly to your bandwidth bill, but it is not a measure of codec efficiency.
(2) Efficiency at equal quality (iso-VMAF BD-rate): the bits needed to reach the same quality, compared against standard x264. This is the codec's actual merit, and every number in the ledger below is of this second kind.
1. Iso-VMAF BD-rate ledger Confirmed
Negative = NormMAP reaches the same quality with fewer bits (a win). Conditions: 720p (Lanczos downscale), against x264 at aq-mode 1, NormMAP strength 0.10, VMAF built-in HD model vmaf_v0.6.1, BD-rate by cubic fit over VMAF → log10(rate).
| Material | Condition | BD-rate | Iso-VMAF range | Verdict |
|---|---|---|---|---|
| sintel (high g2) | 720p aq1 clean | approx. −5% | 85–94 (watchable) | Win, on material that has headroom at the high-quality end. A conservative figure — a CRF-floor clamp in the harness penalised the Norm arm, so the true value is at least this good |
| sintel (high g2) | 720p 3 s aq1 (separate ladder) | −4.08% | 60–93 | Win. Independent reproduction of the module-1 floor |
| water8 (live-action 4K) | 720p aq1, gate off | approx. +4% | 45–81 | Loss. Downscaling to 720p consumed the headroom |
| water8 (live-action 4K) | 720p aq1, g2 gate on | +0.1% | 40–82 | Break-even. Direct evidence that the gate floors the loss at zero |
| 4k-nature | 4K equal-size control (~8 MB) | Loss | x264 VMAF 70 (8.1 MB) vs Norm VMAF 69 (7.8 MB) | At equal size plain x264 is slightly ahead. There is no Norm-specific equal-quality win on this material |
| park_joy (g2 = 0) | 720p aq1 | −5.0% | 12–50 (below watchable) | Floor case, excluded. Not used for operational judgement |
∴ Exactly one claim is confirmed: with the gate enabled, NormMAP needs 4–5% fewer bits at equal quality when the material has headroom, breaks even when it does not, and does not go negative.
A claim we disproved: "a flat −10% in the low-bitrate band" does not hold — the win is around 5% and never crossed the 10% threshold. Reduction is content-dependent.
2. The g2 pre-flight check — deciding before you encode
NormMAP's gain is content-dependent. We therefore compute a g2 statistic from the input (the proportion of low d-values and of high-d edges) and decide before encoding whether the material is a fit. In ledger terms: sintel (high g2) reads as "will work"; water8 after downscaling reads as "will not".
3. The gate — why a miss does not cost you
Where the g2 check reads "will not work", NormMAP passes the material through unchanged (the same path as plain x264). That is what row 4 of the ledger demonstrates: water8, which cost +4.0% (i.e. grew by 4%) with the gate off, lands at +0.1% with the gate on.
For a purchasing decision the relevant property is the asymmetry — a hit reduces your bill, a miss leaves it where it was — and that single row is its evidence.
4. Why module 2 was frozen Frozen
The second module originally claimed −10.03%. Re-measured for its marginal contribution over module 1 (the floor), the contribution turned out to be zero or negative. Three arms measured under identical intermediate conditions:
| Arm | vs x264 | vs module 1 (marginal) | Verdict |
|---|---|---|---|
| Module 1 floor only | −4.08% | — | This is the real figure |
| 1 + 2, initial settings | −3.56% | +0.50% | Zero marginal contribution (slightly worse) |
| 1 + 2, aggressive settings | +3.98% | +7.83% | Clearly worse. The −10.03% claim did not reproduce |
Module 2 is therefore frozen as an off-by-default switch and removed from the product claims. The code remains, but nothing routes through it by default.
5. VMAF underestimates NormMAP (work in progress)
The −4–5% above is measured entirely with VMAF as the yardstick. This week we established that VMAF structurally understates what NormMAP does:
- VMAF only looks at luma. Measured on luma, NormMAP's separation is 1.33×; measured on chroma it is 5.13×. The yardstick does not look at the plane where much of the effect lands.
- In our public NormAV1 switching demo, output scoring VMAF 54.57 — numerically "collapsed" — is one that most viewers cannot pick out against the original. VMAF's collapse and visible degradation diverge.
∴ the ledger's −4–5% is a lower bound, and we expect the figure to be larger when measured against viewing quality rather than VMAF. That expectation, however, has not yet been measured — see §6.
6. What we have not verified Unverified
For the reasons in §5 we expect −20–25% when quality is judged by eye rather than by VMAF. At present this is a hypothesis, not a measurement. The blind-test stimuli (reference plus 8 clips and a sealed key) are prepared, but the assessment has not been run.
The conditions for publishing it are fixed in advance: (1) a blind A/B with multiple subjects, not one; (2) run on a high-g2 material where Norm wins at equal size (4k-nature does not qualify — see §1); (3) a second stage that shrinks the Norm output until the eye detects a difference and compares that point against x264's. When all three hold, the figure and the full procedure go on this page. Independent corroboration with external subjects (a BT.500-style procedure) is the step after that.
- "Half the CDN bill" and "−42%" — withdrawn. The figure came from 4k-nature: "x264 14.3 MB (VMAF 80) vs Norm 8.2 MB (VMAF 69) = −42%". That is a same-CRF comparison — Norm is smaller because its quality is 11 points lower, not because it delivered the same quality for fewer bits. The equal-size control (row 5 of §1) puts x264 slightly ahead. Wherever those figures survive in older material, they are void.
- Compression-history bonus — under investigation. Feeding already-compressed material appears to widen module 1's gain (−1.86 / −2.79 / −3.39% at intermediate CRF 12/24/32), but we cannot yet rule out a geometric artifact, so it is not part of any claim.
- A known defect affects ProRes master input; a fix is pending.
7. Measurement conditions (for reproduction)
| Resolution / band | 720p (Lanczos downscale), 0.3–1.5 Mbps ladder |
|---|---|
| Opponent | x264 at aq-mode 1 (same aq as the NormMAP arm) |
| NormMAP setting | strength 0.10 |
| Quality metric | VMAF built-in HD model vmaf_v0.6.1 |
| BD-rate | Cubic fit over VMAF → log10(rate) |
| Aggregation rule | Read per material; do not collapse to a median. The band below VMAF ~50 is not used for operational judgement |
These figures come from a pre-registered measurement protocol. They shift when the material or the configuration (binary build, preset, thread count, watermark) changes. We recommend verifying on your own footage — free trial.