| # Derivation Contract v1 |
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| ## 1. Purpose |
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| This contract defines reproducible access derivatives for the |
| `maxwellinked/time-lapse-artifacts` archive. It does not define a research task, |
| benchmark, aesthetic ontology, or theory of the recorded practice. |
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| ## 2. Source authority |
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| Every derivative must record: |
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| - source repository ID |
| - pinned source revision |
| - source `record_id` |
| - source repository path |
| - published source Xet file ID |
| - Hub-reported LFS SHA-256 |
| - independently computed SHA-256 of the downloaded bytes |
| - source byte size |
| - source encoded duration |
| - source audio-stream presence |
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| A derivative is invalid if its source identity cannot be resolved, the pinned |
| revision or Xet file ID differs from the published metadata, or the downloaded |
| SHA-256 differs from the Hub-reported LFS SHA-256. Xet identity and byte |
| SHA-256 are distinct fields and must not be compared as if they were the same |
| hash function. |
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| ## 3. Epistemic separation |
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| ### 3.1 Curator facts |
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| Facts established through the source metadata, physical-work review, or |
| documented provenance evidence. |
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| ### 3.2 Unresolved states |
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| Null and `unknown` are valid states. They must not be converted into false, |
| zero, absent, complete, or standalone. |
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| ### 3.3 Deterministic measurements |
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| File hashes, encoded positions, image hashes, Hamming distances, dimensions, |
| and stream properties may be computed without becoming interpretations of |
| skill, intent, quality, completion, or real-time behavior. |
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| ### 3.4 Interpretations |
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| Human and machine interpretations are outside the initial pilot. If added |
| later, they must occupy a separately versioned namespace and may not overwrite |
| facts or unresolved states. |
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| ## 4. Identity model |
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| - `record_id`: persistent identity of one published video object |
| - `work_id`: persistent identity of one curator-verified physical drawing |
| - `derivation_id`: identity of one source object processed under one pinned |
| generator contract |
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| `work_id` remains null unless verified. Filename components such as `Rec01`, a |
| shared date, or visual similarity alone do not establish work identity or |
| sequence. |
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| ## 5. Completeness model |
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| The following dimensions are independent. |
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| ### 5.1 `source_master_status` |
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| - `archival_master`: curator has verified the object as an archival master |
| - `active_derivative`: curator has verified that the object is a shortened or |
| otherwise active derivative |
| - `unknown`: master/derivative status is not established |
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| ### 5.2 `visible_start_state` |
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| - `blank_or_unmarked` |
| - `preliminary_work_present` |
| - `mid_process` |
| - `unknown` |
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| ### 5.3 `visible_end_state` |
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| - `completed_signed` |
| - `completed_unsigned` |
| - `active_work` |
| - `unknown` |
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| These values describe what is documented at the visible endpoint. They do not |
| judge aesthetic success or prove completion of the real process. |
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| ### 5.4 `capture_extent` |
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| - `full_available_process`: curator has verified that the available recording |
| spans the expected visible process range; this does not mean calibrated real |
| session completeness |
| - `starts_mid_process` |
| - `ends_mid_process` |
| - `starts_and_ends_mid_process` |
| - `unknown` |
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| No automated visual inference may populate these fields in the initial pilot. |
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| ## 6. Proxy transform |
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| - video stream only; all audio removed |
| - fit within 1280 × 1280 pixels |
| - preserve stored orientation and aspect ratio |
| - force even output dimensions |
| - 30 encoded frames per second |
| - H.264 using `libx264`, `preset=medium`, `crf=28` |
| - request pixel format `yuv420p`; record the probed result separately |
| - accept FFprobe's `yuvj420p` alias when H.264 preserves full-range 8-bit 4:2:0 |
| values; do not silently force full-range source values into limited range |
| - remove source metadata |
| - enable fast-start layout |
| - record the complete FFmpeg version string |
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| Bit identity is guaranteed only for the recorded generator and FFmpeg versions. |
| Output SHA-256 remains the authoritative derivative identity. |
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| ## 7. Progress-frame transform |
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| - 21 positions: `0.00, 0.05, ..., 1.00` |
| - positions refer to normalized encoded duration, never real drawing time |
| - the final position seeks to the last decodable frame interval before the |
| reported encoded duration |
| - fit each frame within 1280 × 1280 pixels while preserving aspect ratio |
| - JPEG quality setting `q:v=2` |
| - remove source metadata |
| - record normalized position, requested seek time, exact SHA-256, 64-bit |
| difference hash, and Hamming distance from the preceding sample |
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| Repeated or near-repeated frames are reported. The pipeline does not label them |
| meaningless, static, erroneous, or significant. |
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| ## 8. Audio rule |
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| `source_has_audio` reports stream presence. `audio_removed=true` reports the |
| proxy transformation. Neither field classifies audio content. |
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| ## 9. Validation-set rule |
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| The set is selected to expose engineering failures, not to represent the |
| archive statistically or aesthetically. Selection is deterministic and records |
| one or more reasons per row. Wave assignment controls cost; it does not imply |
| importance. |
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| ## 10. Publication boundary |
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| Masters remain in the source archive. Derivatives live in this separate |
| repository. A derivative may be regenerated or superseded without changing the |
| source record. No unresolved source fact may be silently corrected here. |
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