Combining the benefits of makemkv and dvdisaster

[agatek]

DVDisaster is a very nice tool that allows to create a correction file (similar to, for example, par2 files) to enable recovery of damaged disks. The procedure involves creating a disk image and base on this, a correction file with desired redundancy can be created.
Now, when this image file is opened with makemkv it fails like this:

Using direct disc access mode
Loaded content hash table, will verify integrity of M2TS files.
Downloading latest HK to /data/ ...
Saved AACS dump file as /data/**name of the dump file**.tgz
The volume key is unknown for this disc - video can't be decrypted
Failed to open disc

I guess makemkv fails to make the association between the image and the disk content and can not determine the right HK. How to tell/pass to makemkv what key should be used? I understand this key is available (as long as it can read the original BD).

Why to bother - because this would allow to have an extra, safe copy of the disk using only space of the correction file. So for example, a correction file of 10% redundancy is created and the disk is protected as long as the total number of errors on the disk will not exceed 10%. Right now, I understand, the only way to have the whole disk protection is to do full backup.

[thetoad]

I don't understand the Q. Are you asking that makemkv should enable you to make a par2 type file set for a physical bluray so if this physical disc ever has problems in future you can recover it with the par2 type data?

I think its out of scope of MakeMKV, but you can effectively do that today if this is a real concern for you (personally, I'd rather spend the time just backing it up and storing it multiple locations)

1) dd image the bluray to create an encrypted iso
2) start a protected backup into the same directory that you were making the dd image, but stop it once its generated its metadata (i.e. can delete BDMV/CERTIFICATE directories)
3) par2 the dd'd image and the metadata that makmkv created for the protected backup
4) delete everything but the par2 data

in future if you want to recover a bad disc

1) ddrescue the bluray to recover as much data as you could
2) par2 recover the metadata and the missing data that ddrescue couldn't read.
3) mount/extract the recovered encrypted iso into the same directory as the metadata (i.e. where the BDMV/CERTIFICATE folder you deleted earlier) - easiest might be to mount it elsewhere then mount --bind the directories into the proper place.
4) use makemkv normally.

and yes, this is somewhat linux specific instructions.

edit: one thing I should note, is that the above would suffer an issue with bus encryption. Either have to use a drive that doesn't have it, use libredrive to effectively remove it from the drive or have another "hand wavey" mechanism that can remove it.

[agatek]

Hi thetoad,

I didn't mean to implement the functionality of dvdisaster into makemkv.
It is very likely I don't understand how the d/encryption works so maybe the answer is in your last sentence.

Ddrescue faces exactly the same problem as dvdisaster - makemkv can not find the key to get it decrypted, or what is the reason for this message: "The volume key is unknown for this disc - video can't be decrypted"?

Is it the same key that makemkv finds/downloads while reading the physical optical disk?
If yes, is there a way to use the key to decrypt ddrescued image (or in my case dvdisaster image) or this is a completely different issue?

You wrote: "one thing I should note, is that the above would suffer an issue with bus encryption. Either have to use a drive that doesn't have it, use libredrive to effectively remove it from the drive or have another "hand wavey" mechanism that can remove it." Could you please explain this? Is this the reason makemkv reports "The volume key is unknown for this disc - video can't be decrypted"?