Investigations & evidence · DVR, NVR and CCTV disks
A DVR treats its disk as one long loop. It fills the space, returns to the start and writes across the oldest recording, with no view on what that recording shows. Cut the power and the loop freezes where it stands. Everything after that is bench work.
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| The problem | What's behind it | First move |
|---|---|---|
| Staff deleted the clips from the menu | The database entry goes; the video data stays put | Power it down immediately |
| Someone formatted the drive during a repair | A fresh, empty database sits over old video data | Carving pulls the frames back |
| No lights, no boot, no picture | Video sits on the internal disk, not in the electronics | Out comes the disk for imaging |
| It happened three weeks back | The loop may already have passed over it; we check before quoting | One free look settles the question |
| It plays on screen but won't export | A dud USB port, or the export routine is broken | Imaging the disk sidesteps the whole problem |
| Thames Valley Police or a claims handler wants it | An exhibit: MP4 copy, native export, hashes, notes | Flag it when you book the case |
Every item gets its own case number on the day it lands here. An engineer traces the fault, gives you a plain assessment of what is realistically recoverable, and puts one fixed price in writing. The diagnosis is free, you are under no obligation, and chargeable work starts only when you say go.
Our first instruction on the phone is always the same: switch the recorder off at the mains, or take its disk out. Nothing done later matters half as much. Left running, it is still overwriting.
The disk is removed and cloned through a write blocker, sector by sector. After that the recorder can stay dead in its box; every later step runs against the clone, never the original.
Hikvision writes a HIKBTREE index, Dahua its own DHFS tables. Where those structures survive, clips come back tagged with channel and clock. Where they don't, we scan for H.264 and H.265 frames and rebuild playable files.
You get the full list of recovered files first, and nothing is charged until you approve it. Data goes back on fresh media, return postage paid, and the job stays open on our side until you confirm every file opens at your end.
On the 30-day figure: retention is not fixed by UK law — no statute says how long CCTV must be kept. The 31-day convention comes from the storage-limitation rule in data-protection law, and it describes intent, not disk arithmetic. Camera count, bitrate and disk size decide your case. Assume the shorter number.
The insurer asked for the footage nine days on, with the recorder still looping. We took an image of the disk, unpicked its index, and lifted the incident window from sectors the loop had yet to reach. Two exports went back: one to view, one for the claim.
Usually, yes — provided the loop had not come round again before the recorder was switched off. Deleting clears the index only; the footage stays on the disk until fresh recording lands on top.
No. Once fresh video has been written over the old footage, no lab anywhere can retrieve it — which is precisely why switching the recorder off comes before everything else.
Rarely. The recordings all sit on the drive inside, so we take that drive out, image it, and work only from the copy. The recorder is little more than a housing for the disk.
Disk size, how many cameras and what quality they record at all decide it — on a busy system the loop comes round within days. Every footage job is urgent while the recorder is still running.
Loop recording writes over the old footage, and deadlines won't wait. Open a case now — the first look costs nothing and stays confidential.