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PDR / Legal and insurance work / Overwriting, and why the clock runs the job

Investigations & evidence · how long a recorder holds

CCTV footage overwritten, Plymouth. The unit will continue to record over existing footage until you switch off the mains power.

There is no place within the DVR where recordings are deleted, and there is no bin to retrieve anything from. Once the DVR has filled its disk and returned to the beginning, the new recording overwrites the old, and it carries on as long as the DVR has power. No one can work out at a distance how many days that leaves you. To stop the DVR, however, is a simple job taking about 10 seconds, which you can do yourself.

On most jobs, no files means no fee An exhibit from the start The recorder is overwriting it

A quiet word first?
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What is happening on the disk itself.

How the loop worksThe DVR fills its disk completely from one end to the other. At that point, it begins again at the start of the disk and records new footage directly over the old. It continues to repeat this cycle for as long as it has power. Nothing is deleted, no bin fills up, and there is no undo.
No one can quote you a windowNot over the telephone, and not from a make and model number. The key factors are what disk is in the system, how many cameras are recording, the resolution, the frame rate, what compression method is being used, and whether the system records continuously or waits until motion occurs. A figure given without inspecting the system first will just be a guess.
Where the real answer sitsLook at the recorder in front of you. Bring up the calendar for viewing recorded video and note the earliest date shown for each camera. That date is today's answer, and it will continue to advance as long as power remains supplied to the DVR. Write it down before doing anything else.
What written over actually meansEach block on a DVR disk stores one value at a time. As soon as new video occupies that space on the disk, the previous video stored there is lost; there are no hidden layers of earlier video that can be recovered. If the loop reached only part of your requested period, segments of video commonly remain and we will search for them. However, if the loop went right across the period, none of it will remain on the disk. Anyone who tells you they can recover overwritten video is attempting to sell you something.

What each symptom points to.

Not on this list? Call us →
What turns upWhat that points toWhere to start
The unit still has powerEvery hour it operates, it records over the oldest hour it containsSwitch it off at the wall
Nobody has told you how far back it reachesThe capacity of the disk, the number of cameras, and the settings all change itLook up the earliest date
Channels reach back different distancesMovement-only recording on a quiet view fills littleRead every channel separately
The unit died a fortnight backAnything that stopped writing stopped overwriting as wellKeep it off and post the drive
The date you need is no longer listedPieces often remain beyond the indexThe free check determines whether any of your requested period remains
Nobody has opened a claim or an enquiryPaper moves a good deal slower than the diskHave a copy taken today
Sending it to us: once you have your quote, our intake lab in Bristol takes tracked, insured post, and we pay to send it back to you. If you'd like to talk packing through with an engineer before you post it, give us a call. There's more detail on our contact page.

Each stage, in turn.

Every job written up →
01

A number on arrival, then the free diagnosis Free

Whatever is delivered is booked in using a unique reference (case number) on the date it arrives at the bench. The engineer will identify the actual fault at no charge. This gives a straightforward answer on what can be recovered from the drive and what cannot, plus one written quotation. There will be no further activity until you have read and accepted the quotation.

Diagnosis at no chargeA single written figureYou owe nothing yet
02

Nothing further gets written

First, the recorder must be shut off, before anyone reviews footage on it. The disk is removed and copied sector by sector using hardware that does not allow writing to occur at all. Now your position is locked: everything that the loop had not yet reached resides within the image and can never again be altered.

Supply cut firstCloned behind a write blocker
03

Which dates came through

Next, the image is read to find out what it actually contains: the oldest recording, the newest, and any holes in between. Where the loop captured some of your time frame, it shows which half-hours were returned and which were not. All of this reaches you as a written list before anything else is done with the data.

Earliest and latest dates listedEvery hole named
04

Copied out and signed over

Everything that can be read is then transferred to new media as an exhibit: the original files as they were written by the recorder, a version that works on any computer, MD5 and SHA-256 hashes for both, and a dated note of who has held the media. This is how loss adjusters and investigating officers expect it delivered. Another benefit is permanence: from that day the video exists somewhere outside the recorder, so the unit goes back on the wall and the loop decides nothing.

Hashed, catalogued, datedHeld away from the recorder
05

You give the word, and it ships back

Give yourself time to consider it. It costs you nothing. We list all of the files we recover for you before sending out an invoice, and we only ask for payment once you have authorised it. We also buy media specifically for your recovery and send it back to you, with the return postage paid by us. The case stays here on our bench until we have your confirmation that the files open properly on your own machine.

You see the list and decideWritten to fresh mediaWe pay the postage home

What the work keeps showing

  • Usually admin is a step (or more) behind the actual hardware. Claims and enquiries may take weeks for responses. If the bill ends up disputed, copy the video evidence from the equipment before you even begin arguing over who owes what.
  • Failing units are often good luck. Equipment that failed two weeks ago stopped recording at that exact same time, so the video records it made are preserved as they were.
  • Video capture devices write to the disk at different rates. A camera located next to the front entrance captures video at a faster rate than a less active camera in a stockroom, on the same disk. With movement-based recording, areas of slower activity hold historical data from much further back than those of higher activity.
  • Check to see if other drives exist. Typically larger recorders contain multiple drives. A second drive may be used for archiving or for storing "retired" channels, with dates the main (live) drive has already gone past.

Only switching it off at the wall will stop this. Not the menu options, and not a message to whoever set up the device, simply unplug it. This must be your own recorder, or one you have permission to have examined. Once the power is turned off, you can then run things at whatever speed you want. In cases where continued monitoring of the location is required, transfer the hours of footage you need onto a USB memory stick before changing anything, keep the recordings created by your original recorder instead of generating new ones by converting them, and contact us before touching the hard drive. Simply allowing it to run and hoping is how you ultimately lose hours of video that could have been saved.

A job out of the casebook.

PL · PLY-2026-0875FILED ✓

An industrial unit in Cattedown, off at the wall by nine

When they arrived in the morning to find the shutter open and evidence that an intruder had been inside the unit overnight, the manager turned off the recorder at the socket before unlocking. They called us right away. We had the hard drive by Tuesday, and copied all of the data before viewing a single clip. The entire night's footage was preserved along with channel names and timestamps. This was delivered to the loss adjuster within five working days. What was surprising to them was how short a time frame that particular disk had held.

Footage came back intactVerified export

Before you seal the box.

Get these done

  • 1. Take a photo of the screen when it is live and the time shown on the clock
  • 2. Take the recorder off the mains supply
  • 3. Phone us before anyone opens the case
  • 4. Write to your insurance company stating it has been made secure

What to avoid

  • Leaving it powered up
  • Waiting to be asked for it
  • Logging a call with the installer and sitting tight
  • Connecting the drive to an office computer

The questions callers ask most.

How far back does my recorder actually go?

Nobody can tell you that without knowing your system. It will depend on the type of hard drive fitted, how many cameras are feeding into it, the resolution of the images coming from them, the frames per second, and whether it records continuously or only when something is moving. Check the oldest date listed on your playback calendar: that is your answer for today, and it keeps changing.

Is anything left once it has been written over?

No. Once a block has been used for newer video, older recordings are no longer stored on that same block. There is no software or bench procedure that can change this. However, there are exceptions. Depending on how the loop fell across the hours you want to retrieve, parts of those hours might remain in areas outside of the index and be recoverable. A free evaluation will indicate which category applies to you.

Do I pull the plug on it?

Yes, if the premises can go uncovered for a couple of days. Simply shutting off the mains is the only reliable method of stopping the loop. It costs nothing. If the cameras need to continue to record, save the hours you wish to retain onto a USB memory stick first, in the recorder's original native file format and not converted. Then contact us before opening up the unit.

So far my insurance company has made no such requests. Is this even relevant?

Secure it regardless and make a copy as soon as possible. Most claims or enquiries can take many weeks. The device records over itself at whatever rate its current settings permit, which is usually faster. By the time a written request arrives, it will often ask for dates the recorder has already gone past. Copies are inexpensive, and they settle it either way.

Pages people open after this.

Footage for a claim or the police → Camera cards, SD and CF → Flash drives and pens → Evidence and reports →

Every minute it runs, less is left.

Every single minute the recorder continues to record, the clip you want becomes more and more likely to be recorded over for good and your deadline does not change. Begin here. Your first look is free of charge and any information we receive from you is held in confidence.

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