What it is.
An alert is only as good as what backs it up. When a client asks what happened at 2:14 a.m., or a supervisor reviews why a guard escalated, the answer has to be the camera image — not a model’s summary of it. Semaphor treats original evidence as a first-class product feature. Every screen sample and every camera crop it processes is saved as an original image, fingerprinted with an exact SHA-256 hash and two perceptual hashes, and linked to every alert, AI report and guard decision that relied on it.
What is recorded.
- Original images. Each accepted screen sample and each camera pane crop, saved as captured. Derived images, such as background estimates, are stored separately and never substituted for the originals.
- Exact hashes. A SHA-256 of the decoded pixels and a SHA-256 of the saved file, so anyone can check that a downloaded evidence file is the one Semaphor saved.
- Perceptual hashes. pHash and dHash fingerprints that describe what the image looks like, used for camera matching and duplicate detection.
- Source timestamps. When each frame was captured, and which camera view and episode it belongs to.
- Decision history. Trigger reasons, AI assessments labelled with the frames they examined, priority changes with reasons, acknowledgements and closures.
Why it matters.
Judge the pixels, not the paragraph.
AI scene reports are fast and useful, and they can be wrong. Putting the original frames directly beside every AI scene report means the guard checks the claim against the image before acting. That habit is the difference between AI assistance and AI guesswork.
Incident reports that hold up.
When a guard writes up an incident, the frames, times and camera names are already attached to the card. Supervisors and clients see what the guard saw. Our guide to incident reports with video evidence covers how to build a clean report from it.
Accountability for every decision.
When the alert was acknowledged, when and how it was closed, why a priority was changed, what the AI said and which frames it looked at: all of it is on the record. Supervisors can reconstruct any shift.
How it works.
Capture and hash.
Each processed screen, pane crop and background estimate gets a versioned hash bundle: exact pixel and file SHA-256, pHash and dHash.
Link to the alert.
Alert cards, AI reports and guard actions reference the evidence IDs they used. The AI can only cite frames it was actually given.
Export or retire.
Sessions export as JSON manifests with links to the saved images. Guard mode retires old material automatically on a bounded schedule.
Exportable manifests.
A session export is a JSON manifest that lists observations, camera identities, hashes and relative links to every saved image. Hand it to a supervisor, attach it to a client report or archive it under your own records policy.
Bounded, automatic retention.
Evidence is useful; unlimited evidence is a liability. In guard mode, Semaphor applies automatic retention with clear limits. Incident images keep the first and latest frames of each event for a bounded period, subject to a storage budget. Working images and the rolling capture timeline expire in minutes. Closed incident records expire on schedule, and unresolved ones persist until a guard handles them. When storage pressure forces older images out, the incident records that its evidence expired — it never pretends the image is still there. Retention supports your security and privacy posture.
Semaphor retains sampled image sequences for each incident rather than continuous video. Your VMS remains the system of record for full-motion recordings.
Where it matters.
- Cannabis facilities — operations where documented, reviewable surveillance records are part of daily life.
- Hotels — guest incidents and liability claims where the frames and times need to be right.
- Electrical substations — perimeter events that may need to be documented for utility investigations.
Frequently asked questions.
What does the SHA-256 hash prove?
It proves a file’s content has not changed since Semaphor hashed it: recompute the hash on the downloaded image and it must match. It fingerprints content; it does not by itself authenticate which physical camera produced it.
Does Semaphor store full video?
In guard mode, Semaphor keeps sampled original frames for each incident, not continuous video. Full recordings stay in your existing VMS.
How long is evidence kept?
Retention is automatic and bounded, with limits by age and storage budget, and configurable per deployment. We set it to your policy during a pilot.
See the evidence trail behind a real alert: book a live demo or start a pilot.