scales/scale_comparison.md

EventActivityNet Scale Comparison Audit

Status: final scaling verification audit for the candidate Large / Medium / Small release manifests. No manifests or H5 files were modified.

Executive Conclusion

• The recovered Large manifest exactly matches the recovered original Large subset manifest by video ID.
• Small is a strict subset of Medium, and Medium is a strict subset of Large.
• All three scales preserve all 200 action classes present in the recovered Large release.
• The scales are suitable for public release as candidate manifests, with the caveats listed below.

Part A - Large Provenance Verification

Confirmed By Code

Principle	Evidence
Train/validation merge before sampling	load_metadata(paths) merges every provided metadata file into one meta dict before class sampling. The sampling loop iterates over metadata.keys() without split-specific quotas.
Seed	random.Random(args.seed) and np.random.seed(args.seed); default --seed 2025.
Minimum-per-class rule	Initial class-balanced stage uses k = max(5, int(args.class_ratio * len(vids))); default class_ratio=0.2.
Duration stratification	length_bucket_edges(durs) uses np.quantile(durations, [0.33, 0.66]).
Event-friendly definition	event_friendly() returns caption keyword match OR first-frame mean below threshold.
Event-friendly keywords	run, fast, sprint, night, dark, slow-motion
Darkness threshold	default --brightness-threshold 0.4.

Confirmed By Data

• Candidate train/validation pool: 14,926 videos, 200 classes.
• Reproduced class-balanced stage: 2,908 videos, 200 classes.
• Reproduced length-balanced stage: 2,888 videos, 200 classes.
• Original sample_subset caption-duration quantiles: q33=76.306200s, q66=151.323400s.
• Large equals subset_caps_20p.json by ID: True.
• Large split counts: train 2,316, validation 947.
• Large event-friendly ratio from manifest fields: 0.653080.
• Event flags are consistent with keyword OR dark_first_frame fields: True.
• Final Large classes below the initial seed-stage per-class quota: 54. This is a consequence of later global length balancing, not evidence of a different subset.

Inferred

• The released Large subset satisfies the recovered curation principles as the final output of sample_subset.py: it matches the original subset list exactly, preserves all 200 local classes, and reflects the expected duration/event/class-balanced structure.
• Medium and Small preserve the Large release principles by deterministic nested stratification over (split, class_label, duration_bucket, event_friendly), but they are newly generated derivatives rather than historical sample_subset.py outputs.

Deviations / Historical Inconsistencies

• final_large_not_constrained_by_initial_min_per_class_rule: sample_subset.py enforces max(5, int(class_ratio * class_count)) only during the initial class-balanced stage. The later length-balancing stage samples globally from that pool, so the final Large manifest is not expected to retain those initial per-class quotas. Affected classes: 54; largest shortfalls: Swimming 6/15, Shaving 6/14, Baton twirling 13/20, Cleaning windows 8/14, Shoveling snow 9/15, Table soccer 8/14, Archery 9/14, Clipping cat claws 8/13.
• release_scale_duration_buckets_use_src_fmt_dur_not_original_caption_metadata_duration: The scale manifests use src_fmt_dur from verify_all.csv per the scale-construction requirement. sample_subset.py used metadata[v]["duration"] for its original length balancing.
• class_count_claim_203_not_supported_by_local_sources: Local taxonomy/candidate/final files contain and preserve 200 classes; see audit/missing_classes_analysis.md.

Part B - Scale Comparison

Scale	Videos	Hours	Avg dur (s)	Median dur (s)	Train	Validation	Classes	Event-friendly
Large	3,263	106.941600381	117.986	114.242	2,316	947	200	0.653080
Medium	1,537	50.000000128	117.111	114.056	1,074	463	200	0.648016
Small	667	20.000000374	107.946	102.864	473	194	200	0.646177

Duration Bucket Distribution

Scale	Short	Medium	Long	Short ratio	Medium ratio	Long ratio
Large	1,077	1,076	1,110	0.330064	0.329758	0.340178
Medium	512	500	525	0.333116	0.325309	0.341574
Small	247	226	194	0.370315	0.338831	0.290855

Per-Class Deviation From Large

Scale	Max ratio deviation	Mean ratio deviation	Missing Large classes
Large	0.000000000	0.000000000	0
Medium	0.003145020	0.000548689	0
Small	0.006468877	0.001455918	0

Largest Class Gains / Losses

Medium vs Large

Largest gains by class ratio:

• Snowboarding: delta 0.001640, medium count 11, Large count 18
• Building sandcastles: delta 0.001603, medium count 10, Large count 16
• Clean and jerk: delta 0.001565, medium count 9, Large count 14
• Fixing bicycle: delta 0.001527, medium count 8, Large count 12
• Cleaning sink: delta 0.001452, medium count 6, Large count 8

Largest losses by class ratio:

• Removing ice from car: delta -0.003145, medium count 6, Large count 23
• Making a cake: delta -0.001957, medium count 5, Large count 17
• Mooping floor: delta -0.001919, medium count 6, Large count 19
• Cutting the grass: delta -0.001613, medium count 6, Large count 18
• Sumo: delta -0.001575, medium count 7, Large count 20

Small vs Large

Largest gains by class ratio:

• Washing dishes: delta 0.004059, small count 7, Large count 21
• Discus throw: delta 0.004026, small count 8, Large count 26
• Sharpening knives: delta 0.003819, small count 5, Large count 12
• Wrapping presents: delta 0.003786, small count 6, Large count 17
• Table soccer: delta 0.003545, small count 4, Large count 8

Largest losses by class ratio:

• Skiing: delta -0.006469, small count 1, Large count 26
• Capoeira: delta -0.004663, small count 2, Large count 25
• Pole vault: delta -0.003777, small count 3, Large count 27
• Cheerleading: delta -0.003744, small count 2, Large count 22
• Playing harmonica: delta -0.003711, small count 1, Large count 17

Nestedness

• Small strict subset of Medium: True
• Medium strict subset of Large: True
• All IDs unique per scale: {'large': True, 'medium': True, 'small': True}

Published Paper Duration Comparison

Published Large duration: 107.3 h.

Duration source	Hours	Difference from 107.3 h
Release manifest src_fmt_dur	106.941600381	-0.358399619
subset_caps_20p.json caption duration	106.952283333	-0.347716667
verify_all.csv src_dur	106.848348413	-0.451651587
verify_all.csv src_fmt_dur	106.941600381	-0.358399619
verify_all.csv src_dur_est	106.782090037	-0.517909963
verify_all.csv dst_dur	106.785122166	-0.514877834
verify_all.csv dst_fmt_dur	106.939227018	-0.360772982
verify_all.csv dst_dur_est	106.781256732	-0.518743268

The recovered Large IDs exactly match subset_caps_20p.json, so the observed 107.3 h discrepancy does not indicate a different historical subset. It is not explained solely by src_fmt_dur versus other local metadata fields; all local fields are around 106.78-106.95 h. Treat 107.3 h as an approximate/reporting duration unless another historical duration source is recovered.

Part C - Release Recommendation

Recommendation: Suitable as candidate public release manifests after documenting caveats.

Remaining caveats:

• Use 200 classes, not 203, for this recovered release.
• Medium and Small are newly generated deterministic nested candidates; they are distribution-preserving derivatives of Large, not historical sample_subset.py outputs.
• Authoritative scale durations use src_fmt_dur from verify_all.csv. The original subset file caption durations and all local verify_all duration fields are close but do not equal the paper statement of 107.3 h exactly.
• The final Large list can have classes below the initial max(5, int(class_ratio * class_count)) seed-stage minimum because the original script did not enforce that constraint after length balancing.

Machine-readable details are in scale_comparison.json.