The head is now part of a store rather than a script: `finetune_identity.py --stock
stock-lopia` trains on that store's enrolled views (27 views over 7 products, 12
augmented copies each) and writes `<stock>/identity_head.pt`, which ProductGallery
loads automatically.
The first attempt exposed a trap worth recording. A discriminative head has no "none
of the above": trained with an angular margin to separate seven products, it maps
everything confidently onto those seven, including cartons it has never seen.
raw features, threshold 0.55 home shelf 78% accepted foreign shelves 5% accepted
trained head, threshold 0.40 home shelf 58% accepted foreign shelves 44% accepted
Rejection - the gallery's whole point - disappears. The fix needs no retraining: the
two mechanisms fail in opposite directions, so raw features decide *whether* to answer
(they generalise) and the head decides *what* to answer (it discriminates). Measured:
47% accepted on the home shelf, 5% on foreign ones. Lower coverage than raw-only,
which is the honest trade.
The head also needs its own threshold (0.40 against the raw 0.55): a trained head's
similarity scale is its own, and reusing the raw line rejected almost everything it
said.
175 tests pass.
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
The user's objection was right and it changed the design: the tag channel is
sparse in the real world (measured: 0 tags readable at ~2 m on the main shelf), so
packaging recognition has to carry identity. Measured on a 12-class, 57-facing
evaluation set read off the demo shelf, the packaging channel as shipped cannot:
views per SKU embedding top-1 shipped matcher top-1
1 57 % 33 %
2 72 % 27 %
3 75 % 20 %
4 76 % 5 %
Two things follow. First, two views per SKU is where most of the gain is - that is
the enrollment spec (a first scan already produces several facings per product).
Second, the matcher gets *worse* with more views, because its raw inlier score is
not calibrated to be aggregated and it cannot express two views of one SKU at all:
it keys templates by filename.
So identity becomes retrieval: `gallery.py` embeds every enrolled view with DINOv2
ViT-S/14, scores a SKU by its best view, and rejects when nothing is close enough
(an unknown product must come back unknown, not as the nearest stranger). Measured
with held-out views - the gallery never contains its own queries - 2 views per SKU
over 12 SKUs gives 69 % top-1 with rejection working, and the threshold moves the
rejection line.
It is affordable in the live loop only on the GPU: 159 ms per crop on CPU versus
3.6 ms on the M5's MPS, and a live frame only needs its new tracks embedded.
157 tests pass; test_gallery.py covers the retrieval contract (best view wins,
several views are one answer, strangers are rejected) with injected embeddings so
it needs no torch.
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
