dtourolle
4925443e56
Splits the rep4 write-up's key findings into their own linkable pages: - best-model.md: calibration curves first (discriminative power, independent of any threshold), then F1 on the benchmark — LVFace-B Glint360K wins both. - gallery-scope.md: whole vs. cast-restricted gallery, isolated from model and expansion choice — restriction wins on every axis, but isn't a shipped runtime feature yet. - pose-expansion.md: the training-set expand_gallery effect, and the held-out replication attempt that found it doesn't reproduce (5 films, 2 models, after catching and fixing a replay-timeout truncation bug and a bbox first-match-instead-of-best-match bug in the comparison harness itself). An honest null result, with the methodology errors documented since they're exactly the kind that manufacture a false "it works!" finding. - lvface-deep-dive.md: the winning model's held-out generalization gap, its two failure modes (frozen-bbox ghost tracks), and a verified case (cross- checked against Jellyfin's independent cast metadata) where LVFace correctly identified an actor that X-Ray's ground truth failed to credit. Adds a "report-highlights" artifact-registry package (scripts/artifacts/ push_artifacts.sh, pull_artifacts.sh) for hand-picked illustrative frames that aren't reproducible via the automated best/worst montage selection, and wires pulling it into scripts/docs/build_site.sh.
99 lines
5.1 KiB
Markdown
99 lines
5.1 KiB
Markdown
# Deep dive: LVFace-B Glint360K
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LVFace won the model bake-off (see `best-model.md`) and is the shipped default
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embedder. This page is the honest accounting of how it actually performs —
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including where it's wrong, and one case where the ground truth itself is
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wrong and LVFace is right.
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## Training vs. held-out: the generalization gap
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The shipped config (`prob_threshold=0.754, anneal_sec=35.54,
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extinction_sec=57.43, expand_gallery=true`) was tuned against 4 films. Scored
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against the 5 films the optimizer never saw:
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| film | F1 | P | R | TPI | FPI | misid | FN |
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|---|---|---|---|---|---|---|---|
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| Benny & Joon | 83.0% | 89.1% | 77.7% | 15125 | 1846 | 0 | 4337 |
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| Lovelace | 77.5% | 90.3% | 67.9% | 14990 | 1085 | 58 | 7085 |
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| Valerian and the City of a Thousand Planets | 74.1% | 97.1% | 60.0% | 18663 | 548 | 0 | 12467 |
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| Downton Abbey: A New Era | 56.2% | 97.8% | 39.4% | 52027 | 1173 | 0 | 80084 |
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| **The Many Saints of Newark** | **46.3%** | **54.7%** | 40.1% | 15922 | 4394 | **974** | 23791 |
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| **macro average** | **67.4%** | 85.8% | 57.0% | | | | |
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**67.4% held-out vs. 75.3% on training** — an ~8pp drop, and a **37pp spread
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between the best and worst held-out film**. The config does not generalize
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uniformly; two films are outright failure cases, for two different reasons.
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## Failure mode 1: frozen-bbox "ghost tracks"
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Both Many Saints of Newark (974 misIDs) and Downton Abbey (FN=80084, the worst
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recall of the five) trace to the same root cause, verified directly against
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the raw per-frame stream and the HDF5 dump's own detection counts — not
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inferred from the score alone.
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At this second, three of the four labeled boxes ("Jon Bernthal", "Joey Diaz",
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"Billy Magnussen") sit over empty background — a blurred wall, hanging
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plates — with no face in them. The real face in frame carries a second,
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colliding label from another frozen box.
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This is the starkest case: **15 actors named, all wrong, over a completely
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blank closing title card.** Confirmed against the dump directly: `face_count`
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is 0 from this point onward (no detector output at all), yet the same 15
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identities keep appearing with the *exact same bounding box, unchanged to the
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pixel*, for 57+ consecutive seconds.
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This is `SceneTrackerFunc::active_[actor_idx].last_bbox`
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(`src/nodes/scene_tracker_node.hpp`) being re-emitted unchanged — the
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extinction state machine working exactly as coded, not a bug. The film cuts
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from a packed group shot straight into 40+ seconds of blank titles/credits,
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and `extinction_sec=57.4` is comfortably long enough to bridge that entire gap
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without expiring, so the tracker faithfully reports "last known position" for
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a cast that is no longer on screen at all. `extinction_sec` was tuned toward
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long windows specifically because they bridge real gaps (occlusion, a turned
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face) in most training footage — this is the cost side of that trade,
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surfacing only when a film has a long enough faceless stretch to expose it.
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## Failure mode 2: a genuine misID (for contrast)
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Not every held-out failure is a ghost. This is a real face, correctly
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detected, confidently misidentified:
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*(same many_saints_ghost_fpi.jpg frame above also shows Leslie Odom Jr.'s box
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carrying a second, colliding "Michael Gandolfini" label — two real tracks'
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frozen positions happening to overlap, not a detection error.)*
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## Where LVFace beat X-Ray
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Not every "misID" is actually wrong. `second_score.py` counts a name as a true
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out-of-cast misID whenever the named actor isn't in X-Ray's credited cast list
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for the film at all — but X-Ray's cast list is itself incomplete.
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Germar Terrell Gardner — a real, clean, high-confidence detection — is counted
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as a misID here because he doesn't appear in X-Ray's `people.csv` for The Many
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Saints of Newark at all. But Jellyfin's independent cast metadata *does* credit
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him for this exact film (cross-checked via `experiments/manifests/
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jellyfin_casts.json`, a completely separate data source from X-Ray). This
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isn't a lookalike error or a gallery mixup — it's the pipeline correctly
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recognising a real cast member that one ground-truth source happened to omit.
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This doesn't mean every flagged misID is secretly correct — Many Saints'
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974-count total is still overwhelmingly the frozen-bbox failure mode above,
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not uncredited-but-real cameos. But it's a reminder that the X-Ray corpus is a
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convenient, large-scale ground truth, not a perfect one, and the "misID" number
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in any of these tables has some irreducible noise floor from ground-truth gaps
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in the other direction too.
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## Summary
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LVFace is the right default: it wins the model comparison outright, and its
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failures are traceable, understood, and mostly attributable to one tunable
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knob (`extinction_sec`) rather than the embedder itself. The held-out
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generalization gap (75.3% → 67.4%) is real and should be treated as the honest
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expected performance, not the training-set number.
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