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HDR / Evidence and legal work / Overwriting, and why timing decides it

Investigations & evidence · how long footage lasts

Overwritten CCTV footage, Hull. Switch the recorder off; everything else can wait.

Recorders fill their internal storage, cycle back around to the beginning point, and record over the earliest content. The content never gets deleted, nor placed into a bin. It merely continues to be overwritten, hour-by-hour, so long as the recorder unit has power. No one can tell you from the outside how many days that leaves you. We can provide you guidance on how to prevent that process from continuing, and it takes about ten seconds.

Only pay if we recover your data, on most jobs An exhibit from day one It is being written over now

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0800 6890668

What the loop actually does.

The loop itselfA digital recorder continually records data from one side of its memory disk to the other. When it reaches the end of the disk, it returns to the beginning and records over previously recorded data. This cycle continues as long as the device is turned on. Once it starts recording over prior data, it does so indefinitely, with no ability to delete data, place it in a "bin" or perform an "undo".
Nobody can tell you how longNot over the phone, and not just from the make and model. The disk size, number of cameras, image resolution, frame rates, compressions and if it's always running or only when there is motion affect the total number of hours. If someone gives you a number without being able to see the actual system they're guessing.
How you find that outAsk your own DVR. Look through its playback calendar and note the earliest date it shows activity on each individual camera. That's where your footage begins today, and it will continue to move forward by an additional hour with every hour the device continues to run. Write that down first.
What overwritten meansEach sector on a hard drive records only one state per sector. When that state changes due to new video recorded into that sector, all previous states disappear; there are no other layers of data below that can be recovered. Fragments often exist from partially overwritten recordings, and we go after those. But if a complete recording fills the space entirely, nothing will ever come back from that area again. Anyone telling you differently is trying to sell you something.

Putting a name to the symptom.

Not one of these? Ring us →
What you seeWhat the fault isWhat to try
The DVR is still operational.It's always writing over the oldest data entries while the system continues to operateDisconnect power
You don't know how far back the footage goesDisk size, number of cameras and settings all change itLook up the oldest date it shows
One camera goes back further than the othersA quiet channel was being filled slowly with motion recordingDon't just check one channel; check all channels!
The recorder failed about two weeks agoA unit that can't write can't overwrite eitherLeave the recorder turned off; get a quote first, then send the disk
The night you wanted has goneFragments of data can survive outside the indexA free check will settle it either way
No claim or investigation has been initiated yet.Any request in writing will take longer than the loop.Get a copy made now.
Sending it to us: ring first or fill out the form to request a quote. Send the recorder disk (or camera card) via post to the Leeds intake laboratory (insured and trackable). Alternatively, drop the recorder disk (or camera card) off there, Monday to Friday, 9am to 5:30pm. No appointment needed. We pay for its return journey. Call prior to sending if you would like one of our staff to check the packaging with you. All information about how to send is on the sending page.

The stages, one by one.

The casebook in full →
01

A case number first, then a free diagnosis Free

Every piece of gear that shows up receives a case number on the very same day it arrives. An engineer examines it and determines what is really wrong with it and there is no charge for this. We give you straight language about which files we will be able to copy from the disk and which ones we won't be able to. Then we provide you with a single price quote, in writing, based upon these findings. We don't begin working on anything until you agree to the quoted price.

The diagnosis is freeOne price, put in writingNothing to pay yet
02

The disk stops writing

Firstly remove the recorder from operation, rather than looking at it, and then take the disk out. A complete copy will be made of the original hard-drive in segments (blocks) while being behind a write-blocker. At this time the position is fixed; any data that was not reached by the loop will remain intact in the image. In addition, no new data can be added to those areas.

Power off firstA write-blocked copy
03

What survived, and when

Data contained within the image will now be identified for what is truly there. This includes the oldest segment of video that remained on the drive, the most recent, and any "gap" in between. For example, a partially overwritten disk indicates which half-hour intervals came through, and which did not, and you get this information as a list prior to proceeding with additional processing.

The date range read offGaps listed plainly
04

Held, then handed over

The results of the imaging process will be written to new media in an evidentiary format: as the recorder's own files and a playable copy of the original recordings (on any compatible machine), along with MD5 and SHA-256 hash values of each file segment, and an entry indicating who handled the evidence at what date. This provides an insurance investigator or law enforcement officer with an easily understood evidentiary item. Additionally, once the imagery exists independently of the unit, the device can immediately be returned to operation and the recording loop will no longer matter.

Hashed, listed, datedKept clear of the loop
05

You sign it off, then it comes back

You will not be charged while you think about this. First, you receive a list of everything that was recovered from the drive. Once you have seen the list and given us the go-ahead, the bill comes next. Files are returned to you on media purchased specifically for this job and we cover the return postage as well. Your job is kept open by us until you can view them on your personal computer.

You approve the listing firstCopied onto new mediaReturn postage at our cost

What we see on the bench

  • Paperwork takes longer than a disk: claims and investigations move for weeks. Get the video evidence first, then sort out the argument.
  • A dead recorder can be good news: if the unit died a fortnight ago, it has not written since then, so all it captured is still on there.
  • Recording channels do not fill uniformly: a busy entrance and a quiet stockroom use the same disk but not equally. As well, due to motion recording, cameras with low usage reach back further than busier cameras.
  • A second hard drive can store the period: larger units will have two drives or more, to hold an archive or older sets of recording channels. If one drive holds the current set of active channels then the second drive may still contain data which has been overwritten by the live disk.

The only single thing that will stop this process: turn the power off. This is not a menu selection, nor a setting, nor are you calling the installer; it is the switch on the wall. Everything else can happen as fast or slow as you need. If the cameras have to remain online (because the site requires monitoring) export the time period you wish to save to a USB device first, save the recorder's original file format, do not create a new version by re-encoding, and contact us prior to accessing the device. What doesn't work is simply continuing to leave the unit on, and hope for the best. Every hour the recorder continues to run removes the oldest hour from the disk.

One case from the casebook.

HU · HUL-2026-0875LOGGED ✓

A Sutton Fields industrial unit, off at the mains

There was a burglary during a Sunday night. The next morning, the manager discovered that the shutter was open; they turned the recorder off at the wall before opening and called us immediately. By Tuesday, the disk was removed and copied. All of the Sunday night footage was recovered along with the camera names and times. Within a week, the insurance company received our complete package of data. What surprised them was how little the disk was actually holding.

CCTV video came back wholeConfirmed export

Before you box it up.

Do these first

  • 1. Take a photo of the display and its clock.
  • 2. Turn the recorder off at the mains.
  • 3. Call us before removing the disk from the recorder.
  • 4. Notify your insurer in writing that the evidence is preserved.

What not to do

  • Leaving the recorder on (running)
  • Wait for the insurer to ask
  • Ring the installer and wait
  • Put the disk into a PC

What we get asked on the phone.

How long does my recorder keep it?

You cannot determine this without actually reviewing the system. The amount of space available on the disk determines how long the recordings will last. Additionally, the number of cameras feeding into the recorder affects how quickly it fills up. Camera resolution also plays a significant role in determining how much information is stored per minute of recording. Frame rate also plays a factor in terms of storage requirements. Finally, recorders that continue to record 24/7 (all the time), regardless of activity or motion, require more disk space than those that only record when they detect motion. Your playback calendar indicates what the oldest date remaining is. Review it now.

Can overwritten footage be recovered?

No. No software and no laboratory changes this. As soon as new video is written across those blocks the earlier recording is not available in any form on that disk. Where only part of the period was written across, fragments outside the index often survive and are worth carving for. Which one you have is determined by the free check.

Should I unplug the recorder?

Yes, if you can manage without the cover for a couple of days. Turning it off at the mains is also the only sure-fire way to stop it from continuing to overwrite. Also, it doesn't cost anything. If you need to continue monitoring the site then export what you need to a USB drive first, retain the native files, and call before doing anything further.

What if the insurer has not asked yet?

Secure it regardless. An inquiry into a claim comes weeks after an incident; a recorder captures data according to how it is set (usually much faster) and by the time a formal request is received the requested information may have been overwritten. Copying everything now is inexpensive and will answer the question either way.

What people read after this.

Clips for an insurer or the police → SD, microSD and CF cards → USB sticks and pens → Forensics and evidence →

The recorder is overwriting it now.

The clip you wish to obtain is currently being recorded over; the deadline has not changed. Log a job. The initial review will cost you nothing; your comments remain confidential.

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