Making data recovery easier

Discussion of advanced MakeMKV functionality, expert mode, conversion profiles
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n0va49
Posts: 2
Joined: Wed Apr 17, 2024 9:11 pm

Making data recovery easier

#1 Post by n0va49 » Wed Apr 17, 2024 9:17 pm

Hi,

I'm dealing with trying to get an error-free rip off of a BluRay and it would be helpful if MakeMKV had some extra convenience features.

Firstly, I'm not sure if the 'mkv' maker (as opposed to the 'backup' function) correctly verifies the checksums of the files? When I 'backup' my discs I get an error report of which files and approximate offsets of data corruption due to hash check failure.

Secondly, it would be very helpful if the 'backup' feature could be instructed to do a single file (like a single .m2ts file), and even better if I could specify a data range to extract. Often the errors are localized to a certain area of the disc and I have to spend quite a long time reading the rest of the disc just to check to see if I got all of the scratches off, etc.

Thirdly, it would be really great if the tool could output a list of checksums per block of the file - say every 4MB or something, give me a SHA1 hash or similar of that byte range of the file when it successfully extracts, so that when I piece data together from separate rips I can have confidence that the entire file is intact.

Is there anything existing that could already help this process along? Imagine I have two discs, one with an unrecoverable scratch near the beginning, and another with an unrecoverable scratch near the end, and I would like to splice together different segments of the raw files to get a 100% good rip.

Thanks.


n0va49
Posts: 2
Joined: Wed Apr 17, 2024 9:11 pm

Re: Making data recovery easier

#3 Post by n0va49 » Thu Apr 18, 2024 5:14 am

Thank you for that info. It's good to hear that something to help recovery is planned.

As for the hashes, my understanding is that the hashes on disc are the hashes of the encrypted files, not decrypted, so it doesn't help when trying to stitch together decrypted files. Although I suppose an idea is to try and stitch together the encrypted files and use the hashes to verify at that stage.

dcoke22
Posts: 3077
Joined: Wed Jul 22, 2020 11:25 pm

Re: Making data recovery easier

#4 Post by dcoke22 » Fri Apr 19, 2024 12:11 am

It is my understanding that MakeMKV uses the hashes to make sure that what's read from the optical disc is correct. This is probably the most likely source of error. Decrypting the files, combining them and writing them out to disk is unlikely to be problematic.

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