# Docs: replay-input format spec + downloadable example CSV

**Task**: AZ-896_replay_format_docs_and_example_csv
**Name**: Author the operator-facing format spec for the (video, CSV) replay input pair, plus a minimal downloadable example CSV
**Description**: Operators using the replay/demo path need to know the exact CSV schema the system accepts, the hard contract (video t=0 ≡ CSV row 0; video must be nadir; UAV must already be airborne at t=0), and have a downloadable example to copy from. Operators today have no entry point that documents this.

**Complexity**: 1 SP
**Dependencies**: AZ-894 (the adapter that consumes the format — the doc describes what AZ-894 accepts)
**Blocks**: AZ-897 (UI links to the docs page and serves the example CSV)
**Component**: docs (_docs/04_release/)
**Tracker**: AZ-896 (https://denyspopov.atlassian.net/browse/AZ-896)
**Parent Epic**: (none — cycle-4 replay-input redesign)

## What

- Author a docs page at `_docs/04_release/replay_input_format.md` (or wherever the operator-facing docs land in cycle 4)
- Schema table: column names, units, types, expected rates, required vs optional
- Constraint statements up top, before the column table:
  - Video: nadir camera; UAV already airborne at frame 0
  - CSV: row 0 timestamp == video frame 0 timestamp; `Time` column starts at 0.0; rows monotonic and uniformly-spaced
- Ship `_docs/04_release/example_data_imu.csv` — a minimal valid example (e.g., 20 rows = 2 seconds at 10 Hz)
- Cross-link from the AZ-897 replay UI "Download example" button

## Acceptance Criteria

- **AC-1**: Schema page documents all 19 columns of the Derkachi CSV with units and types.
- **AC-2**: The three hard constraints (nadir / airborne / aligned-start) are stated up top, before the column table.
- **AC-3**: The example CSV (≥10 rows) passes through the AZ-894 CSV adapter without errors.
- **AC-4**: The page is reachable from the AZ-897 UI's "Download example" link.

## Out of scope

- Multi-schema support (PX4, generic MAVLink dumps).

## References

- Companion: AZ-894 (CSV adapter), AZ-897 (UI), AZ-895 (auto-sync deprecation)
- Source fixture: `_docs/00_problem/input_data/flight_derkachi/data_imu.csv`, README at `_docs/00_problem/input_data/flight_derkachi/README.md`
