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HikVision DVR

19 Posts
9 Users
Posts: 5135
Illustrious Member

The overwriting process isn't linear considering the timeline, there are big chances that the needed data or parts of it are still available!

@JaredDM nobody can recover overwritten data, but since here we talk about video content data, if overwriting wasn't 100%, there are chances to recover dirty frames, still having parts of the original data

Define "dirty frame", please.

It is pretty much binary, at disk level a given sector has either been overwritten or it hasn't.

Assuming, only because of the time passed and on the features of the unknown and undocumented overwriting mechanism that something has been overwritten is as arbitrary as assuming that it has not.

As a matter of fact, if the presented data is correct

Data is from April 4th, 2018. Apparently system was set to start overwriting after ten days. We were not able to copy the hard drive until 4/18/18.

Everything is possible. 😯

We don't know WHEN the 10 days overwriting loop starts, nor how much data 10 days of recording use of the disk space, we don't even know if the recording was "motion controlled" or "continuous" and - in the case of the latter - how much compression is affected (or not affected) by a "static" scene.

Let's say that the 10 days was set because - roughly - 10 days of recording equates maximum to 1.5 TB (or 3/4 of the drive capacity), i.e. for each day there is at most 150 GB recorded, while an eventless day is more like 100 GB.

On days 1-10 the first 1.5 Tb or less are written.

What happens on day 11-20?

1) the recorder continues linearly to record past the 1.5Tb until it gets to 2 Tb, then wraps around.
2) the recorder re-starts from sector 0 (the last 500 GB of the drive are NEVER written)
3) the recorder re-starts from a *random* sector.

if #1 on day 15 (i.e. 18/04 if day 1 is 04/04) anything between 0 and 500 GB from previous recordings may have been NOT overwritten
if #2 the data is overwritten and lost
if #3 who knows?


Posted : 28/04/2018 12:28 pm
Posts: 5
Active Member
Topic starter

I ran the HikV Recovery demo software. The demo provided a text file with a long list of dates and times including the following from the time period I am looking for

2018-04-04 11-01-23 - 11-12-35.264
2018-04-04 11-12-35 - 12-08-32.264
2018-04-04 11-15-56 - 11-27-45.264
2018-04-04 11-20-40 - 11-47-50.264
2018-04-04 11-21-53 - 12-09-42.264
2018-04-04 11-27-45 - 11-28-26.264
2018-04-04 11-28-18 - 11-48-26.264
2018-04-04 11-28-26 - 11-36-29.264
2018-04-04 11-36-29 - 12-23-05.264
2018-04-04 11-47-50 - 12-55-00.264
2018-04-04 11-48-26 - 12-35-27.264
2018-04-04 12-08-32 - 12-11-13.264
2018-04-04 12-09-42 - 12-29-02.264
2018-04-04 12-11-13 - 12-23-15.264
2018-04-04 12-23-05 - 13-30-14.264
2018-04-04 12-23-15 - 12-49-12.264

I presume these are the video clips that are recoverable? Can anyone verify that this software works to extract the clips? If so, well worth the cost but trying to do my due diligence before spending $1000 of my bosses money.

Posted : 30/04/2018 11:03 pm
Posts: 792
Prominent Member

@ares99 Pretty big money for unsure results…

@jaclaz your theory is right, in practice for this Hikvision recorder your assumed #3 applies (if #3 who knows?)

Posted : 01/05/2018 5:49 pm
Posts: 65
Trusted Member

I recently had a DVR recovery case infront of me and after a lot of trying using all different tools and softwares I failed, only to find out the files had been corrupted.

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Posted : 27/07/2018 10:38 pm
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