Tech Peak » Deleted and Overwritten CCTV Video Files – Learn in Detail

Deleted and Overwritten CCTV Video Files – Learn in Detail

by Expert Advice

Summary: In this post, we will learn about Deleted and Overwritten CCTV Video Files.

If a video has been destroyed, can it be recovered from the hard drive? What causes data to be deleted? Is it possible to have video surveillance footage removed on its own? When CCTV footage is erased or overwritten, how can we recover it? Is there a programme that can help you quickly and easily retrieve essential videos? When it comes to DVR and NVR video recordings, these are among the questions that pop into people’s heads.

Why is closed-circuit television (CCTV) so crucial in our daily lives?

CCTV cameras provide you with the benefit of extra sight. Public locations are better protected thanks to their help. CCTV cameras are installed in offices in order to safeguard valuables and keep an eye on them at all times. CCTV cameras offer security and monitoring, and footage is recorded on hard drives and media in multichannel DVR systems.

Damage or loss of video recordings from the DVR can occur for a variety of reasons, including but not limited to:

Deleted deliberately (An attempt to cover up a cyber-crime by purposely erasing evidence of it. Any Cyber Crime Investigation Expert can assist you in gaining a thorough understanding of the situation.)

  • Error in omission
  • Damage caused by water, collision, or fire.
  • Damage to the medium on which the film is stored (e.g. HDD or SSD).
  • An infection spread by a virus
  • Information that has been scribbled over (As a result of numerous DVR recordings, preceding footage is overwritten, resulting in the loss of that footage.)

Is it possible to have CCTV recordings instantly deleted?

No. Deletion is always done manually (for example, film purposely destroyed to conceal a crime), although previously recorded material might be automatically deleted or lost due to data overwriting if the storage capacity is reached and newer footage has to be stored.

What is the difference between deletion and overwriting CCTV Video Files?

Learn more about this by diving further into the subject matter.

A local hard drive, a cloud server, or an offshore server are all used to store CCTV footage once it has been captured and stored on a local hard drive. Typically, old data is overwritten by new data by default after 15 days or a month depending on the amount of storage available in the DVR/NVR, and therefore previous data is no longer accessible.

How data is saved on a hard drive or any other storage device will be examined in this section. ‘ Sectors can be found on a hard drive. 512-byte sectors make up the smallest physical storage region on a disc. Digital data is stored in the form of bytes. Eight bits make up a byte. It’s either 0 or 1 for each bit. The binary number system is named as such because it uses just two digits, 0 and 1.

It is not necessary for a file to be removed from a hard drive in order for the operating system to reclaim the space used by the file. When a file has been erased, it is automatically removed from view and the previously occupied space is shown as free.

Technically, the file that was accidentally deleted is still existent in the physical sector in which it was (which is now designated as empty) and may be restored using a recovery method.


Then, let’s add another level of complication. Files are continually being written to and stored on the hard drive as time passes. As a result, it will write data into the “perceived” vacant space, and the space previously merely indicated as “available” will now be used to store the new files.

It is now impossible to restore this previously deleted file, as the original data has been replaced with the data that comprised the content of the new file that was put in its place, making it difficult or impossible.

In other words, if you want your data or footage back, don’t overwrite it! “. If you need to recover erased data, you may want to exercise caution when it comes to overwriting.

If a file is overwritten, the data cannot be retrieved. Because the bytes formerly held by the first file have been replaced by the bytes from the second file. At this point, the trial is generally seen as having come to a close. Things are somewhat different when it comes to video.

So, what are your options for retrieving corrupted or erased CCTV footage?

We’ve arrived at the heart of the situation now. On a hard disc, CCTV video is written in a completely different fashion than other types of data. As a way of illustrating my point, I’d like to share an example.

Specifications and parameters are included in the purchase of a CCTV camera. FPS, or the number of images displayed in a second, is one of these. To put it simply, 24 frames per second is the rate at which the CCTV takes and records images to its DVR hard drives. Data on CCTV systems is not often arranged into clusters like it is on regular Windows hard drives, that are encrypted and have an operating system that does so. Using the example of a 24-frame-per-second CCTV camera, the number of frames that may be retained with no or very small variations in information is fairly large. As a result, in cases when some frames are physically overwritten, the movie may be rebuilt using the remaining frames.

As an extra precautionary measure, if a frame is repeated more than “x” times in rapid succession, the camera will note that the content of the previous “x” frames’ sectors has not changed and will not waste time or resources rewriting the data in those sectors. Forensic analysis shows that, while being labelled as carrying data from a current video recording, these sectors really contain data from a prior video frame, which was written to the sector in question. There are many earlier video frames that may be patched together and voila! we have successfully retrieved the (so-called) overwritten footage.


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