Investigations & evidence · erased recorder disks
The recorder is still writing while you read this, and that is the whole problem. Deleting through the menu drops one row from the unit's index; the video blocks stay where they are, in the queue for the loop. Get the power off early and most of the footage returns with its camera and its clock attached. Once the loop has been over those blocks, none of it does.
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| What you see | What the fault is | What to try |
|---|---|---|
| Someone deleted the recordings on the unit | An index row went; the picture data did not | Power off, right now |
| The box reformatted itself after a fault | A format writes a blank index and not much else | Carving copes with that, so the odds are decent |
| It carried on recording for days | Every extra hour of recording bites further into the oldest material | Send the disk today |
| The oldest recording is later than the date you want | Almost certainly written over, though the free check proves it | That check costs nothing |
| Clips play with no channel or timestamp | Carved video keeps the picture, not the labelling | Expected, and marked on the file list |
| Files left by an earlier attempt do not open | Raw video streams were pulled but never containerised | We wrap them into MP4 files that play |
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.
Power off the recorder, take the drive out, image it through a write blocker. From then on nothing more can be lost: every block the loop had not yet reached is preserved in that image.
The rest of the work happens on that image. We look for the maker's own filesystem: a Hikvision's HIKBTREE, a Dahua's DHFS. Where enough of it survives, what comes out carries the true channel name and the real recording time. That is the version a loss adjuster takes without argument.
With no structure to follow, the whole image is searched for the byte markers that open each compressed frame, H.264 and H.265 alike, and what turns up is assembled into clips an ordinary player will run. The file list marks the ones that held their timing, and the ones that did not.
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.
Loop recording, plainly: the disk is cut into blocks of equal size and filled in order, first to last. Reaching the last one, the recorder returns to block one and writes straight over what is sitting there. A deleted clip therefore lasts precisely until the write head comes round to that spot. Pulling the plug is not a precaution before the recovery. It is most of the recovery.
Someone behind the counter had cleared down footage that looked long past use. The theft was in the middle of it. What saved it was the recorder being stopped within a few hours. For four of the five missing days the index entries and their timestamps were still there. The fifth came back as carved video: it plays, but nothing names it.
Usually, yes. A delete removes the recorder's catalogue entry and does nothing else. The blocks holding the pictures stay put on the disk until the loop works its way back to them. Cut the power and nothing moves after that.
The new recording sits in the same blocks the old one used, and a platter stores one state in a block, not two. Nobody can promise a result once that has happened, and anyone who does is selling.
Often, if enough of the maker's index is still readable. Where we have to carve frames out of the raw sectors instead, the pictures come back but the labelling usually does not. The file list we send says which clips arrived without it.
It depends on the number of cameras, the bitrate they record at and the size of the disk. There is no standard figure, whatever you have been told. Add cameras, or add movement for them to record, and the oldest footage goes sooner.
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.