Responding to original poster:
1)Â Physical images required to enable analysis
In my experience, one must create true physical forensic image of any DVR's internal hard drive in order to be able to work with the data obtained from the DVR hard drive.Â
Unlike other computer systems in which a logical image will typically capture files and folders, logical images of DVR internal hard drives will NOT recover any files nor folders in my experience. I do not know why logical images of DVR drives will not work in most cases but maybe Jaclaz has insight.
DVR Examiner;s quick start guide (DVR Examiner 3 (DVR-Examiner-Quick-Start-Guide.pdf (dmeforensics.com))) recommends using a hardware write blocker and connecting the original evidence to one's forensic analysis workstation running DVR Examiner.
IMHO it is better to first create a write-protected bit-for-bit physical image of the original evidence DVR hard drive(s) and then analyze the resulting forensic image file or make a true clone of the original evidence using the physical forensic image and then analyze the cloned hard drive.
2)Â Purchase the same DVR hardware and related DVR maker's software
Once the original evidence has been cloned, it is possible to buy the same make and model of DVR as the original evidence, insert the cloned drive, and then use the original DVR's software to search and create clips as needed.
3) Option #3 as stated multiple times above is to buy and use specialized software such as DVR Examiner.
In my experience, data from deleted or formatted DVR drives is not supported. One reason could be that the method of overwriting is not clear. Further most DVRs use proprietary OS and file system. The existing tools support recovery of active data from the disk if the DVR is password protected and the password is not available to the forensic examiner.Â
Try DVR Examiner from DME Forensics. I've used it for several cases and found it to be not only user friendly but performs a thorough examination of the device.
I agree. I think it is the best tool, at least to perform a metadata analysis, I don't know if it can perform a carving. I have used it twice and it is very good. I used it with hard drives recorded by Dahua devices. The good thing is that DVR is accepted by the Courts.