Evidence work · disks lifted from CCTV and DVR boxes
A DVR fills its disk, goes back to the start and records over the oldest blocks. Age is the only thing it sorts by. It has no idea that one hour holds a break-in and the next holds an empty yard. Cut the power, wherever in Hull the recorder sits, and that stops. From then on it is bench work, done on a copy.
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| What you see | What the fault is | What to try |
|---|---|---|
| Someone erased the clips from the menu | The listing has gone; the video has not | Take the power off now |
| The installer formatted the disk again | A fresh empty index laid over the video | We carve frames off the image |
| No lights, no output, nothing | The video is on the disk, not the electronics | The disk comes out and gets imaged |
| That happened a couple of weeks back | The recorder may already have gone over it — we can check | The free diagnosis settles it |
| Plays on the screen, exports nothing | A dud USB port, or export firmware with a bug | We pull the clips off our copy instead |
| An insurer or a solicitor has asked to see it | Exhibit pack: original clips, MP4 copies, hashes, notes | Mention it when you book |
Each item that arrives gets a case number the day it lands. An engineer looks at it and finds the real fault, and that costs you nothing. You are told in plain terms which files can come off the drive and which cannot. A price follows — one figure, written down. No work starts until you have seen it and agreed to it.
We say the same thing on every footage call. Pull the plug, or take the disk out of the box. Nothing else we do matters as much, because a recorder left running is busy overwriting the clip you came for.
The disk goes on a hardware write blocker. The imager reads every sector; nothing goes back the other way. Once we hold that copy the recorder stops mattering, and all the remaining work happens on the image.
Hikvision writes a HIKBTREE index. Dahua uses its own DHFS tables. If either still parses, every clip comes back named for its camera, with the time it was recorded. If not, we carve H.264 and H.265 frames straight out of the image and rebuild them into files that play.
You are not billed while you are still thinking. The list of what came off the drive goes to you first, and the invoice waits on your word. Files go home on media bought in for the job, with the postage back on us. We keep the job open until you have opened them on your own machine.
On retention: nothing in UK law sets a minimum time for keeping CCTV. The month-long figure people repeat comes out of data-protection guidance about not holding footage for longer than the purpose needs — it is not a technical limit. What your box actually holds comes down to how many cameras there are, what bitrate they run at, and how big the disk is. Plan for the lower end.
Nine days went by before the insurer asked for the footage, and the recorder had been left running the whole time. We took the disk out, imaged it, read the index and pulled the relevant minutes off blocks the box had not reached yet. Two copies left here: one for viewing, one to go on the claim file.
Often we can. It turns on whether the recorder was stopped before the write head came back round to those blocks. A delete takes the entry out of the index. The pictures stay put until fresh video is written across them.
Then it has gone. New frames replace the old ones on the disk and nothing survives underneath. No lab can undo that, ours included. It is why we ask you to cut the power first.
Rarely. A DVR is a box, a board and a hard disk. Your footage is on the disk. The board can be finished and it changes little. We lift the disk out, take an image of it, and the job runs on that.
That is down to disk capacity, camera count, and what bitrate each camera runs at. A busy forecourt can work right round in a few days. For as long as the recorder is running, assume you are short of time.
The clip you want is being written over while you read this, and the deadline has not shifted. Log a job. The first look costs nothing, and what you tell us stays private.