Investigations & evidence · recorder disks that were erased
Pull the power now and most of it is still recoverable. While you read this the recorder has not stopped writing, and that is the whole problem. Deleting from the menu takes one row out of the catalogue; the video blocks stay exactly where they are, queued and waiting to be reused. Cut the mains soon enough and most of what you want comes back with its camera name and its clock attached. Let the loop reach those blocks and none of it does. The look costs nothing and the work is £400 + VAT. Disks reach the bench from every sort of place — a stable block out at Hungerford, a joiner's yard on the Headley Road estates in Woodley, the back office behind a shop counter.
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| What you are seeing | What is likely wrong | What happens next |
|---|---|---|
| Somebody deleted the recordings at the unit | The index lost a row. The pictures stayed where they were | Take the power off at once |
| It reformatted itself after a fault | A format writes a blank index and leaves the rest alone | Carving handles that, so the odds are reasonable |
| It carried on recording for several days | Each extra hour of recording takes another bite out of the oldest material | Send the disk to us today |
| The earliest recording is later than the day you want | Almost certainly written over, though the free check will confirm it | The check itself costs nothing |
| Clips play with no camera name and no clock | Carved video keeps the picture and loses the labels | Expected, and noted on the file list |
| An earlier attempt left files that will not open | Raw video streams were pulled out and never put in a container | They get wrapped into MP4 files that play |
A case number goes on your device the day it reaches us, and an engineer then finds the real fault — free, and before anything else happens. You are told plainly what will come back and what will not, with one fixed figure in writing beside it. Nothing chargeable starts until you have read that and said yes.
Power the recorder down, remove the drive, and clone it behind a hardware write blocker. From that moment nothing further can be lost: every block the loop has not yet reached is inside the image, whatever becomes of the recorder later.
All of it runs on the image. First comes a search for the filesystem the manufacturer laid down — HIKBTREE on a Hikvision, DHFS on a Dahua. If enough came through, the clips arrive named by camera and stamped with the real recording time, and no loss adjuster argues with that version.
Where no structure is left to follow, the image gets swept for the byte markers that begin a compressed frame — H.264 and H.265 both — and whatever surfaces is built into clips that any player will open. The file list records the ones that kept their timing, and the ones that lost it.
You see the file list first, then decide. Nothing is invoiced until you have said yes, and on most jobs there is no fee at all if the data does not come back. What we pull off goes onto media bought in for your job, and the postage home is ours. The case stays open on the bench until you tell us the files open on your own machine.
Loop recording, plainly: the drive is divided into equal blocks and written from the first to the last. At the last, the unit turns back to the first and records over what it finds there. An erased clip is therefore readable only until the head returns to it. Cutting the power is not a preliminary to the recovery. It is most of the recovery.
A member of staff had deleted footage that looked long past its use, and the record of the theft went with it. What saved the job was the recorder being unplugged inside a few hours: four of the five missing days still held their index entries and their times, so those clips returned with names and dates on them. The fifth had to be carved out of raw blocks — it plays, but nothing tells you when.
Usually. A delete crosses the entry out of the recorder's catalogue and stops there. The video itself is still lying in its blocks, and it goes on lying there until the recording head works back round to that stretch of the disk. Take the power away and nothing shifts at all.
Because the newer recording sits in exactly the blocks the older one used, and a magnetic block holds one value rather than two. Past that point nobody can promise you anything, and a firm that does is selling.
Often, so long as enough of the manufacturer's index can be read. Once the job drops to carving frames out of raw sectors you get the pictures and lose the labelling. The file list we send marks which clips arrived unlabelled.
Camera count, bitrate and the size of the disk decide it between them. Whatever you have been told, no standard figure exists. Add cameras, or put more movement in front of the ones you have, and the oldest recordings go sooner.
The recorder is still writing, and each time it comes round it takes more of what you need. Pull its power now, then get it to us. The first look costs nothing, a fixed figure follows in writing, and nothing you tell us goes anywhere else.