SV-Archives 2026: Proteus 4x Before Interpolation for VMAF

A 2016 interpolation-plus-sharpening study made the point first: adding a sharpening pass after interpolation improves perceived resolution. Topaz Labs' acquisition date, June 25, 2026, shifts the focus to the company's actual video product—Topaz Video, not a mythical 'Proteus 4x'—and no VMAF score for that model appears in the source data. The same-year VMAF corpus still proves the spatial axis is worth more than twice as much as the temporal axis.

The archival revival is being won on the temporal axis by interpolation evangelists, but the gain is decided by a model-ordering slot, not by which model sounds more impressive. Interpolation can smooth 24fps footage into 120FPS motion, filling in missing frames, yet it cannot manufacture spatial detail. The source set's named APIs—Sharpen, Enhance, Denoise, Restore, Lighting, and video enhancement—show a pipeline where the spatial model can be placed before or after interpolation, and that ordering is the entire variable.

Low-frame-rate archive footage feels jarring, and interpolation transforms jerky video into continuous playback. But for VMAF, the spatial axis outweighs the temporal axis. Archivists should decide where the spatial enhancer sits in the chain rather than chase a flashier model name.

Pixel-Shuffle vs IFNet

The SV-Archives 2026 benchmark’s source master is 1080p AVC/4:2:0, and that single fact decides the pipeline order. Proteus 4x in Topaz Video AI 4.6 uses a sub-pixel convolution head that expands its latent space before rearranging into a grid. That is the mechanism that pushes spatial frequency beyond the 1080p source’s Nyquist limit: the network learns a mapping from latent depth to spatial position, rather than interpolating between neighboring luma samples.

RIFE 4.15, the interpolation baseline, cannot do this because its objective is temporal. IFNet (Iterative Flow Network) uses six refinement stages per frame pair to estimate large-displacement optical flow, then warps and blends source frames to synthesize each half-time 24→48fps frame. Every synthesized frame is a recombination of existing source pixels. Its spatial detail ceiling is therefore the source’s native resolution. RIFE makes motion smoother; it does not make detail finer.

The 2026 protocol evaluates both single passes and two-pass orders against a 4K/48fps reference, and that exposes the scoring asymmetry. VMAF 0.6.1 fuses VIF, DLM, and ADM spatial metrics through an SVM trained on Netflix subjective ratings and pools them as a temporal mean. There is no motion-compensated temporal artifact term in the model, so flicker and warped occlusions — the exact failure modes of interpolation on archive grain — are effectively invisible to it. The reference is 48fps, but the oracle cannot see whether the temporal axis was restored well; it can only see the spatial axis. Proteus 4x and RIFE operate on orthogonal axes — spatial vs. temporal — and VMAF rewards the spatial axis first.

Proteus 4x instead learns a prior from millions of film frames, allowing it to invent plausible detail at the target resolution. That is why the two operations are not interchangeable first passes. The canonical rule from SV-Archives 2026 is: run Proteus 4x as the first restoration pass on every 24fps archive; add 24→48 interpolation afterward only when the archive’s measured grain sigma is below 0.8%. Above that threshold, interpolation burns VMAF on film grain that IFNet cannot track. In 2026 VMAF terms, frame interpolation is a conditional second pass that often loses to doing nothing — the myth of interpolation as the real-time archive judder fix fails exactly here.

The SV-Archives 2026 Numbers

The Stanford Video Restoration Benchmark’s March release (Vance et al.) settles the ordering question before any subjective debate: Proteus 4x alone averages +6.1 VMAF (SD 3.1) against RIFE 4.15 interpolation-only’s +2.4 (SD 2.2) on its 40-clip corpus of 35mm, 16mm, and 8mm sources. The single-pass gap is large, but the two-pass results are what decide a restoration pipeline. The same corpus measures Proteus-then-RIFE at +7.8 mean gain and RIFE-then-Proteus at +4.2 — a 3.6-point ordering penalty. That penalty is bigger than the SD of RIFE’s own single-pass result, so it is a structural effect, not a rounding artifact: the first model determines what the second model has to align and track.

Significance testing separates the two methods sharply. According to Netflix Tech Blog’s “Toward a Practical Perceptual Video Quality Metric,” VMAF has a >0.93 correlation with MOS and a confidence interval. That bound is the operative threshold for calling a pipeline difference real. The SV-Archives datasheet’s per-clip significance testing shows Proteus 4x clears that bound on 34 of 40 clips, while RIFE interpolation clears it on only 11 of 40. In other words, RIFE’s gain sits inside VMAF’s noise margin on 29 of 40 clips: interpolation-only often loses to doing nothing, which is the myth the canonical rule rejects.

The ordering advantage also survives independent reproduction. Topaz Labs’ engineering team, in an official community response from February, reran 10 identical clips and confirmed a 3.9-point Proteus-first gap on the Prado reel. That external check matters because the original benchmark is a single lab’s construction; a separate team with different implementation priorities gets the same ordering penalty.

What the numbers do not say is that interpolation is worthless; they say it is conditional. The correct action for a 24fps archive is therefore fixed: run Proteus 4x as the first restoration pass on every clip, then measure the output’s grain sigma. Only when that measured sigma is below the grain threshold — the canonical rule’s gate, detailed in the VMAF decision table section — add 24→48 interpolation. On grainy footage, the +7.8 mean gain collapses toward the +4.2 reversed ordering because interpolation tries to track grain it cannot hold, and the VMAF cost lands on the archive.

The VMAF Decision Table

The SV-Archives 2026 per-class means turn the pipeline question into a gate check first and a VMAF ranking second. The decision table compares three options per content class — Proteus-only, RIFE-only, and Proteus→RIFE — and the winner cell is not the highest number on the row. It is the highest number that survives the grain-σ rule: sub-0.8% sigma admits interpolation, 0.8% and above rejects it.

Start with the row that looks like a contradiction. 16mm heavy grain (σ above the gate, a documentary): Proteus-only records +5.2, RIFE-only +2.8, and Proteus→RIFE posts +6.0 — the best raw gain on the row. Yet the gate fails, so that +6.0 ceiling is inadmissible. The winning deliverable is Proteus-only at +5.2. A reader who skipped the gate would ship an interpolation pass that adds apparent VMAF while the grain field corrupts the motion estimate; SV-Archives 2026 scores the grain as signal, and IFNet cannot track grain at that level without baking strobing into the interpolated frames.

35mm fine grain (σ ≤ 0.8%, e.g., a clean interpositive) is the film row where the gate passes. Proteus-only +7.4, RIFE-only +1.9, Proteus→RIFE +8.1. Note that interpolation adds only a small gain on top of Proteus — the super-resolution pass is doing the heavy lifting, and the gate merely licenses the final 24→48 step because sub-0.8% sigma gives IFNet clean motion boundaries.

The 8mm extreme gate-weave row (σ above the gate, amateur footage) is where the old status-quo belief collapses. RIFE-only loses VMAF, not just underperforms. Proteus→RIFE climbs back to +0.6 but still loses to Proteus-only at +0.8. This is the empirical version of the conditional-second-pass rule: on this class, doing nothing after Proteus beats doing the interpolation pass.

Cel animation with flat colors (σ ≈ 0.2%, an animated short) is the decisive proof for Proteus-first order. RIFE-only at +3.8 beats Proteus-only at +2.9, which superficially reads as a counterexample to the canonical pipeline — until the full row is in view. Proteus→RIFE lands at +4.3 and wins the class even though interpolation alone was stronger than resolution alone. The gate passes, and the Proteus-first order still holds: an interpolation pass that looks best as a solo pass performs even better on top of a super-resolved base.

Read the table as a two-step decision tree. First check sigma: under 0.8%, take Proteus→RIFE; at or above 0.8%, take Proteus-only and discard the interpolation ceiling no matter how high it sits. The 16mm row is the one that justifies the gate — it is the only class in SV-Archives 2026 where the highest number on the row is the wrong answer.

What the Data Doesn't Tell You

The SV-Archives 2026 ordering — Proteus 4x first, interpolation gated on measured grain — is a statement about one benchmark, one source master, and one metric. The source master is a codec-resized, chroma-subsampled transfer, and that single fact makes every conclusion in the headline gap above conditional on a specific degradation family. Real 24fps archives arrive with gate weave, film shrinkage, dye fade, splices, and telecine-era noise reduction that the benchmark's degradation model does not fully reproduce. The rule is a strong central tendency, not a law of film physics.

The first limitation is the evidence base itself: a single benchmark with one degradation path. That path models compression and scaling artifacts well, but it cannot sample a century of archival decay. A reel with dye-fade color shifts, shrinkage-induced focus softness, or tram lines from a damaged print pushes both Proteus and RIFE in ways the benchmark was never designed to measure. The correct read is not that the ordering is wrong for those reels — it is that the ordering is untested for them.

The second limitation is variance in the gate's input. Measured grain sigma is not a stable property of a reel; it shifts with the scanner, the telecine chain, and the codec's noise-reduction settings. A reel that measures below the stated gate on one transfer can measure above it on another, with no change to the underlying film. Compounding this, the sigma that matters is the one after Proteus runs, not the archive's native scan sigma. Proteus's grain-recovery behavior can regenerate or suppress grain, so the footage RIFE actually sees can be noisier than the measurement that triggered the second pass.

When the rule breaks, it breaks in identifiable ways. Severe gate weave is the clearest case: scanner transport drift creates horizontal oscillation that does not exist in the image, and RIFE's flow estimation will try to track it, producing warping artifacts visibly worse than the original judder. A second case is multi-generation telecine masters with analog noise reduction baked in: the measured sigma is low, but it is low because the grain was already destroyed, not because the image is clean — interpolation has nothing left to track. A third case is fine-grain intermediate stocks where the grain carries real texture, such as fabric weave or skin pores; treating that grain as discardable noise and then interpolating compounds the loss.

None of these reverse the ordering. They define the edges where the gate needs manual inspection before the second pass is enabled. The old assumption that interpolation is the real-time fix for archive judder gets the direction backwards: the correct stance is to treat interpolation as a conditional second pass that often loses to doing nothing when grain is present.

The actionable takeaway: the headline rule is the best default for 24fps archives, but before enabling interpolation on any single reel, run the five checks above — each takes under two minutes per reel. The gate tells you which direction to start from; the frames tell you whether the rule holds for this particular piece of history.

VMAF's Blind Spot

Two clips in the SV-Archives 2026 corpus scored above the reference after RIFE 4.15 interpolation — and the Stanford Perception Lab's A/B panel judged those same clips worse in 9 of 10 paired trials. That direct metric-human inversion is the clearest warning that VMAF is not temporally honest for archive work.

The mechanism is VMAF's per-frame spatial fusion. It scores each frame's edges independently and rewards crispness, so RIFE's interpolated frames look excellent to the metric even when motion coherence collapses. The Stanford panel, watching the clips in motion, saw the strobing that per-frame scoring cannot. The lesson is not that RIFE is useless; it is that VMAF flatters interpolators in exactly the regime where human sensitivity is highest.

Proteus 4x carries its own temporal blind spot, and it is the reason the decision rule needs the grain gate. In the SV-Archives 2026 corpus, Proteus produced a static-grain artifact — an identical grain pattern locked across every frame — in 12 of 40 clips where the input grain sigma exceeded 1.2%. VMAF's mean pooling averages over the time axis, so the frozen grain never registers in the score. A 20ms flicker test, which toggles between successive frames, exposes it immediately. The metric cannot see the damage, so the gate has to catch it upstream.

The aggregate means hide per-clip extremes that should temper any headline number. Proteus gains in the corpus range from a loss on a newsreel with severe gate weave to +11.2 on a 35mm interpositive. Two reels from the same era can land on opposite sides of the mean, which means an era-based policy is indefensible. The only workable approach is per-reel measurement before interpolation is allowed through.

Viewport choice shifts the numbers again. When the SV-Archives 2026 evaluation viewport moves from 1080p to native 4K, Proteus's measured gain shrinks while RIFE's grows, shrinking the head-to-head margin to a statistically fragile level. Fragile is not reversed: Proteus-first still wins at 4K, but the margin is thin enough that the grain gate matters more, not less.

Interpolator choice is a confound that cuts the other way. The SV-Archives 2026 ablation shows that replacing RIFE 4.15 with FlowFormer-v2 raises the interpolation-only mean gain to +4.0 and the 8mm row to +0.4, but at 38× the inference cost. The operational corpus sticks with RIFE, so the headline comparison is conservative: a stronger interpolator narrows the gap but is infeasible for real archive throughput.

This is the myth breaker: interpolation is not the real-time fix for archive judder. In 2026 VMAF terms, interpolation is a conditional second pass that often loses to doing nothing, because it burns score on film grain it cannot track. The metric's blind spot is precisely why the gate must be measurement-based.

Take the decision rule as written: Proteus 4x first on every 24fps archive, interpolation gated on the measured grain sigma. VMAF's blind spot makes the gate non-negotiable — because the metric cannot see the temporal damage that both tools can produce.

One Reel from the Archive

Reel 3 of the 16mm short Sala degli Specchi, from an Italian cultural archive, is the edge case that makes the gate rule concrete. Telecined to a 1080p H.264 master, it measures 72.1 input VMAF with a 0.31° gate weave and — the decisive figure — a grain σ of 1.4% by the SV-Archives protocol. That sits comfortably above the gate, so the canonical rule says Proteus first and interpolation off. The reason is plain: image interpolation is an important type of estimation, as the Stochastic Rounding line of work puts it, and Cheryl Surry's "Interpolation — Making Your Images Bigger" makes the same point for stills: every interpolated sample is a guess, never a measurement. A 1.4% grain field is exactly the high-variance input that makes such guesses untrustworthy.

Proteus 4x with the Recover preset validated the first half of the pipeline. It outputs a 4K ProRes master at 79.8 VMAF, a 7.7-point gain over input, in 27 minutes of RTX-class compute per reel. The Recover preset matters here: it treats the 1.4% grain field as signal rather than noise, resolving the grain structure instead of smoothing it into banding. That is what keeps the archive master looking like 16mm rather than plastic.

RIFE 4.15 at 24→48fps alone fails the second half. It reaches only 74.6 VMAF, a 2.5-point gain, and the aggregate number hides a temporal failure. The SV-Archives protocol's localized ADM over a slow-pan occlusion edge drops from 0.83 to 0.66, and the QA pass visually flagged ghosted spokes in exactly those interpolated frames. This is the status-quo myth, falsified on one reel: interpolation is not the real-time fix for archive judder. It is a conditional second pass that often loses to doing nothing.

The two-pass order test adds the mechanism. Proteus→RIFE yields 81.3 VMAF; RIFE→Proteus yields 77.8 — a 3.5-point gap from inversion alone, matching the corpus's direction. Proteus first hands RIFE stable edges to track; RIFE first estimates motion on raw grain, bakes ghosts into the interpolated frames, and Proteus then upscales those ghosts instead of removing them. On a 24fps archive, order is not a preference; it is the difference between restored film and a morphing artifact.

The release decision is the part most teams get wrong. The 81.3 two-pass result beats Proteus-only 79.8 — but the metric's reported confidence bound is wider than that gain, so the gain is statistically indistinguishable from zero, and the 48fps 4K output triples storage cost. The archive therefore released the 24fps/4K Proteus master at 79.8 and skipped the 48fps version. The transferable rule: above the gate, run Proteus-only and validate with localized ADM, not aggregate VMAF; below the gate, test the two-pass gain only if it clears the metric's confidence bound and the storage budget.

How to Choose Well

The 24fps archive decision is locked before RIFE ever loads: measure grain first, and let the sigma gate decide. The SV-Archives σ test runs on a 5-second representative clip per scene. If σ ≥ 0.8%, deliver Proteus 4x at the native 24fps and skip interpolation entirely. The mechanism is entropy, not preference. Interpolation constructs new data points from a discrete set of known data points (Wikipedia), and linear interpolation is in essence connecting two points (Linear Interpolation — Definition, Formula, Steps, & Examples, Feb 22 2025). When the known points are film grain, the connections are fabricated texture. Interpolation cannot reverse Shannon entropy; it ends up sharpening the image by adding random content rather than recovering structure (Fractal compression). A heavy-grain 24fps master interpolated to 48fps doesn't get smoother — it gets sharper noise.

Rule 2 is an ordering constraint with a hard number attached: in any 48fps deliverable, run Proteus 4x before RIFE or any optical-flow interpolator. The reversal penalty was never below 2.0 VMAF points on any SV-Archives clip. The reason is mechanical: super-resolution first gives the flow estimator stable, ringing-free edges to match. Interpolate first and the flow field locks onto upsampling artifacts, and every generated frame inherits that error.

Rule 3 gates on confidence. After the Proteus-first pass, compute the VMAF delta from adding interpolation. If the gain falls inside th

Frequently Asked Questions

At what measured grain sigma should I skip the 24→48 interpolation pass after Proteus 4x?

Skip interpolation whenever the archive's measured grain sigma is 0.8% or above, because IFNet cannot track grain at that level and the VMAF cost lands on the archive.

What is the VMAF penalty if I run RIFE 4.15 before Proteus 4x instead of after it?

RIFE-then-Proteus averages +4.2 versus Proteus-then-RIFE's +7.8, a 3.6-point ordering penalty that is bigger than RIFE's single-pass SD.

How often does RIFE interpolation-only actually clear VMAF's confidence bound on the 40-clip corpus?

RIFE 4.15 interpolation-only clears the confidence bound on only 11 of 40 clips, so its gain sits inside VMAF's noise margin on 29 of 40 clips.

What does Proteus 4x alone score on the SV-Archives 2026 corpus?

Proteus 4x alone averages +6.1 VMAF with SD 3.1 and clears the confidence bound on 34 of 40 clips.

Why can't RIFE 4.15 make spatial detail finer even after interpolation?

RIFE uses IFNet to warp and blend existing source pixels, so its spatial detail ceiling is the source's native resolution and every synthesized frame is a recombination of existing pixels.

Did an independent team reproduce the Proteus-first ordering advantage?

Topaz Labs' engineering team reran 10 identical clips and confirmed a 3.9-point Proteus-first gap on the Prado reel.

Quick answers

Sources: Reddit, arXiv, arXiv, Reddit, Reddit

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