How to recover a damaged DVD (Linux)

[antibody]

Hello, I'm trying to recover a damaged DVD.

Usually I save my DVD using: makemkvcon backup --decrypt --cache=512 --noscan --robot --progress=-same disc:sr0 ./my-dvd.

When the DVD is damaged, makemkvcon exits with an error "timeout on logical unit".
I found an interesting page from a preservation team of the NYPL: https://nypl.github.io/ami-preservation ... -lg-drives.
They fallback to ddrescue when MakeMKV fails. The idea is interesting because ddrescue is able to create a "map file" and merge multiple incomplete copies together to "fill the gaps".
Is ddrescue really able to read (even encrypted) data from a DVD that has copy protection? What if the device is a libredrive?

Thank you.

[blind-s33r]

I have used this method to rip some stubborn and scratched dvds that didn't want to work with makemkv... its hit or miss if it will work with a damaged disc but its worth a shot...
Edit: fair note, if its an lg drive it will probably return junk data instead of trying to get the actual data due to jamless playback, will only work on a pioneer or possibly older non lg dvd drives.

[flojo]

... a "map file" ...

The map is similar to windows "defrag" visual output which is, the sectors of the UDF filesystem are tracked for which sectors have failed and failures are retried individually and on successful retries the data is inserted into the correct position. The type of data doesn't really matter and as blind-s33r has stated, different drives have different success rates.

To expand on "junk data", I'm not sure how ddrescue works, but the most (dare I say sophisticated) version of this was a script by a "release group" for Playstation over 25 years ago. It used a tool from cdrecord to do it, but on success it rationalized the data it recovered to the preceding data, so it recognized that if the recovered data was to belong to a audio file but the data didn't look right, then the data was flagged as junk. So, make sure whatever tool you use is at least somewhat shielding against junk.

[antibody]

Thank you. Would any tool like ddrescue be able to dump a DVD with copy protection using a libredrive ready device (scratched or not)?

[kaysee]

Yes, you read the data from the disc and copy it into an image file. That image file is mountable and can then be decrypted, or you can use MakeMKV integration to play the DVD image as if playing an encrypted DVD.

Rescuing data is a lot easier if you have multiple copies of the disc, even if they are all damaged. Also, it helps to use multiple drives. Just be careful about drives that do not produce error signals and instead deliver bad data from damaged parts of the disc, which will contaminate the rescued data. LG drives with the "jamless" playback feature do that. Apparently Pioneer BDR-TD05 slim drives also do it, which is disappointing.

[antibody]

Do you know if the verbatim 43888 is returning invalid data from damaged parts of the disc? I guess not according to the timeout error.
Are you saying that with a libredrive enabled device, I don't need makemkvcon anymore? I could just rely on any copy software + any software using libdvdcss for decryption?

[kaysee]

MakeMKV seems to do a number of things which other copy software might not, which you would have to check. For example, for blu-rays it uses the hash tables on discs to check whether what was read is correct. Also, MakeMKV seems to do some apparently worthwhile things to adjust the reading speed at various parts of a disc.

I would expect the Verbatim 43888 to return invalid data in damaged parts of discs, but this would depend on the particular firmware. If the drive is an LG and has LG's jamless playback feature, then it is not good for data rescue. If it is an LG and uses some other firmware, or if it is a Pioneer, then it would require experimentation. Given that the point of this is to work with problematic discs, I would not want to try it with a drive whose behavior itself is unknown.