STANAG 4609: the KLV metadata, and not the motion imagery

STANAG 4609 promulgates a profile rather than a self-contained format. The profile delegates its field dictionaries to documents published by other bodies, chiefly the Motion Imagery Standards Board, so implementing it means implementing those documents and saying which ones.

The metadata a full motion video stream carries is the part that makes the imagery usable as intelligence: a precision time stamp, platform position and attitude, sensor pointing, frame centre coordinates, target locations and, where present, moving target indications detected within the frame.

The item dictionary in question defines 141 items. Any conformant reader is required to skip items it does not know without failing the packet, which is what makes a partial but honest implementation a valid one.

Motion imagery arrives at a command post as pictures, and pictures are not decision inputs until something states where the aircraft was, where the sensor was pointing and when.

Translating the metadata into the same canonical objects as radar, ADS-B and ground moving target reports lets an imagery derived observation be correlated with the rest of the picture without the imagery leaving its own pipeline.

Because the metadata is small and the video is not, a deployment can carry the decision relevant part of a full motion video feed across a link that could never carry the feed itself.

Ingest takes one key length value metadata payload, being one or more Local Set packets, and produces an Entity and an Event per packet in wire order. The Entity is the platform.

The implemented item set is the set this repository has met on a pinned wire capture, plus a nested set item and the items demonstrated by the source document's own printed worked examples. That is 44 of the dictionary's 141 items, and every remaining row is recorded as not yet implemented in the published coverage document rather than left unstated.

An item outside the implemented set is not an error. Its octets are parked under an unknown items attribute and its tag number recorded, and the packet still translates, as the standard requires.

Nothing in the witnessed item set identifies an airframe, so the platform identifier is packet scoped and says so. Consecutive packets from one aircraft therefore receive different identifiers, and the cost is stated rather than hidden behind a fabricated continuity.

The precision time stamp is not UTC. The source document defines it against a time system based on the SI second with a fixed offset from atomic time, and the adapter applies the correction and leap second terms only when the packet carries them, recording which terms were available on every object.

This is the first binary format in the layer with a real integrity gate: the Local Set defines a mandatory checksum. A packet whose checksum fails is translated and flagged rather than refused, because discarding two dozen otherwise well formed items on a 16-bit disagreement destroys the evidence a consumer needs.

Egress reproduces a payload byte exactly for objects that came from this adapter, including the original octets of any item whose length diverged from the dictionary.