2026-09-29 23:52 UTC
Replies (9)
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@neon_nova@lemmy.dbzer0.com 2026-09-30 00:18
Just curious, but why? Can you elaborate on what you are trying to achieve?
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@ArsonButCute@programming.dev 2026-09-30 01:05
I’d recommend ddrescue over dd for optical media backups only because if you’ve got bad blocks it will try them again at a different speed/angle
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@eleijeep@piefed.social 2026-09-30 08:48
I would look at the tools that the preservation groups use for doing this. The optical media layouts are funky and IIRC using dd on the block device is not enough to archive a bit-for-bit copy. There are details about the track layout and so on that need to be recorded separately. This is why formats like BIN/CUE exist. eg. https://wiki.redump.info/Redump#Technical_Questions
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@doomsdayrs@lemmy.ml 2026-09-30 10:08
ddrescue can do a really good job. But for blueray you’ll need a patched firmware.
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@MonkderVierte@lemmy.zip 2026-09-30 10:21
dd is neither the best nor a suitable method (dd is a scalpel not a shovel, use cp or cat). But optical media are tricky either way. redumper was made for a disc preservation initiative.
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@non_burglar@lemmy.world 2026-09-30 14:47
Blueray have anti-copying built into non-data areas, plus Cinavia DRM on the content most of the time. If you are hoping to make a playable bluray, use one of the tools that reads past both and creates a non-drm image. Depending on where you live, this likely breaks copywrite, but isn’t illegal.
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@Majestic@lemmy.ml 2026-09-30 23:21
This is silly. You’re approaching this with wrong-headed thinking. Just use makemkv. What you will have if you used hacked firmware to bypass physical anti-copying methods present on BluRay discs to actually get a bit for bit copy of your disc is a useless blob of encrypted data that you have no way of verifying for accuracy (that it was copied correct or that the disc itself didn’t have subtle physical damage which gave you something damaged because you can’t play it to verify) and which you have no way of using. You’ll have no way of ripping it or turning it into usable data in future if your disc does go bad because no one else uses this method so there’s no software that will allow you to turn this encrypted blob easily back into a playable movie and to burn it to a new BluRay writable disc would break laws anyway because you’re engaging in duplication and secondly all BluRay authoring (burning) programs are built around building and burning unencrypted video files to a disc not around burning an encrypted blob to a disc (often specific sectors containing specific data must be written to specific parts of the disc to make it playable, something no public program will help you with when trying to bit for bit copy in reverse and which blindly bit for bit copying at low level isn’t likely to achieve). Everyone else breaks the encryption and dumps a copy of the disc including the AACS keys and certs to prove ownership and you should do the same rather than thinking you’re particularly special or vulnerable. If you’re that much an enemy of the state or media companies they’ll do you just as much for having the encrypted copies and state you had INTENT to break it if they’re trying to make an example out of you because you’ve pissed them off. In practice no media company is likely to go after someone breaking the encryption while retaining the discs and keeping the copies only for themselves. There’s simply no incentive to harassing paying customers in that way if you’re not uploading the contents or hosting a for-profit Plex or Jellyfin server of the contents or burning bootleg copies of the films. You’d have to go around publicly bragging in your own name about breaking the encryption and pretty much dare them to get you for them to know or care enough to do anything about it short of you otherwise breaking the law as I outlined above.
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@WarmApplePieShrek@lemmy.dbzer0.com 2026-10-01 14:35
There’s no such thing as a bit-for-bit copy of anything, you are always deciding what to copy and what not to copy. When you copy a file you might or might not copy the last modified time. Optical disks use error-checking codes. You usually don’t want to copy those. Even on a non-encrypted disk you don’t want to copy a scratch on your disk onto a new disk with a scratch, you want to decode it and then encode it again to one with the scratch patched over. And it would make your file bigger for no reason when copying to a medium that can’t scratch. ISO format is designed for computer disks. It doesn’t work for audio disks or other types of things you can put on a CD. ISO has the bitstream as a computer reads the filesystem, which is already after several layers of decoding. Audio CDs don’t use that decoding so they can fit more data, so they just can’t fit in an ISO file. Encryption is like this too. If you could just copy an encrypted disk as an ISO and it would still work, that’d be shitty encryption so they wouldn’t bother with it. They use tricks to put data outside of the normal copied areas. A really old form of copy protection was to mess up the lower layers - write a sector that would look so scratched it was unreadable, and if you can read it, it must be a copied disk. Or write the same sector several times, so the drive will find a different version of it depending on where it started from. The PS1 wrote the track a bit wobbly, like the CD writer was drunk, but not so wobbly the PS1 couldn’t read it, then used the shape of the wobble to encode a signature that said it was a genuine disk. Don’t ask me how Bluray DRM works, I don’t know it, but it must be using similar kinds of tricks. Storing data in the disk’s barcode was another trick some consoles did.
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@dt3@lemmy.zip 2026-10-08 20:09
Use dd