Evidence work · disks out of DVR, NVR and CCTV units
A recorder writes until the disk is full, then loops back to the beginning and paints over what it laid down first. Age is its only rule; it cannot tell your break-in from an empty forecourt at 3am. Pull the power and the loop halts there. From then on the work is done on a bench, from a copy.
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| What shows up | What has gone wrong | Do this now |
|---|---|---|
| Somebody deleted the recordings by hand | The index entry went; the frames did not | Cut the power right now |
| An installer reformatted the recorder's disk | A blank index written on top of the footage | We sweep the disk for frames |
| Dead — no lights, no picture | The footage sits on the disk, not the board | We lift the disk out and image it |
| The incident was two weeks ago now | The loop might have passed over it already — we will check | The free look gives the answer |
| Plays on screen, will not export | A failed USB socket, or buggy export firmware | We export off the image instead, which works |
| An insurer, or the police, wants to view it | Exhibit pack: native clips, MP4, hash values, report | Say so when you book it in |
The diagnosis costs you nothing. Every item that arrives is logged under a case number of its own, and an engineer works out what has actually failed — then tells you plainly which files can come back and which cannot. The price follows that: one fixed figure, in writing, and no work begins until you have read it and said go ahead.
Every call about footage starts the same way. Take the plug out of the wall, or lift the disk out of the recorder. Nothing that follows counts for as much, because a running box is quietly writing over the thing you need.
The disk comes out and goes behind a write blocker, so our imager can read every sector and send nothing back. Once that copy exists the recorder is out of the story, and the rest of the job is done on the image.
Hikvision lays down a HIKBTREE index; Dahua keeps DHFS tables of its own design. Where those structures still read, each clip returns labelled with its camera and the hour it was shot. If they are gone, the image is swept for video frames — H.264, H.265 — and rebuilt into files that play.
Nothing is billed while you are still deciding. A complete listing of what came off the drive reaches you first, and the invoice only follows your yes. Files travel back on media bought new for the job, return postage ours, and we do not close it here until every one of them opens on the machine you will use.
About that thirty-day rule: there is no UK law setting a minimum period for keeping CCTV. The 31 days people repeat is really the storage-limitation principle out of data-protection law, which is about purpose, not about how much a disk holds. Your real retention is decided by camera count, bitrate and disk size. Assume the lower number.
The insurer came looking for the video nine days on, and in all that time nobody had switched the recorder off. We imaged the disk, unpicked the index, and recovered the minutes that mattered from blocks the loop had not reached yet. Two copies went out: one to view, one to go with the claim.
Usually, yes — as long as the box was stopped before the loop worked back round to that part of the disk. Deleting a clip only drops it from the index; the frames sit where they were until newer video is laid over the top.
It is. When fresh frames land on the same blocks, the earlier picture stops existing, and no lab anywhere can bring it back. That is why we ask you to pull the plug before anything else.
Seldom. Strip a recorder back and it is a metal case wrapped around a hard drive; the video sits on that disk, not on the electronics. The disk comes out, gets copied, and the job runs on the copy.
That comes down to disk size, camera count and the bitrate each one records at. A busy yard can come full circle in a few days. While the recorder is powered up, treat the clock as running.
While that recorder keeps writing, the clip you need is being covered over — and your deadline has not moved. Book it in. The first look is free, and it stays private.