DVD Decrpypter Exact Copy?, Is It A Clone Of Original DVD

[prbatman]

Hi Everyone.

Just a quickie.

I use Exact Audio Copy to back up my CDs to get exact relicas(But I have to change the offset of the drive)

Does DVD Decrypter do the same thing for DVDs....give you an exact bit for bit back up of the original.Is there any offset issue when decrypting DVDs?

So in theory if I rip an original DVD to HD using DVDDecrypter and then record those files to a DVDR,Re-rip the DVDR.The rip from the DVDR should be exactly bit for bit the same as the original DVD Rip.

Would you recommend using an md5 signature to make sure files stay the same if storing on external drive.

Thanks in advance,

Ian

[skebenin]

In short, yes. A copy of a DVD should be an exact copy (discounting CSS encryption of course).

Unlike CD audio, DVD was designed from the get-go to be data. All DVDs are some variation of data. It would be more appropriate to compare DVD copying to CD-ROM copying.

It is built in error correction that ensures that a DVD rip is digitally accurate. In effect, every sector of the DVD has a signature (not MD5, but something similar) to ensure that it is read correctly. Of course the error correction goes beyond a simple signature - as it's name implies, the error correction can actually correct errors in the sector.

Ripping an audio CD is different because there is little or no error correction. Without error correction, you *will* get uncorrected errors, and errors rarely repeat themselves exactly, so two rips will be slightly different. Even a product like exact audio copy doesn't guarantee an absolutely accurate copy - only a statistically reproducible copy. Luckily for disks in reasonably good condition, statistically reproducible is so close to accurate as makes no never mind.

[yoda313]

Hello,

So in theory if I rip an original DVD to HD using DVDDecrypter and then record those files to a DVDR,Re-rip the DVDR.The rip from the DVDR should be exactly bit for bit the same as the original DVD Rip.

As skebenin wrote Dvd decrypter does essentially do a bit for bit rip.

HOWEVER - you can only do a 1:1 backup of dvd9 discs if you use a DUAL LAYER DVD RECORDER!

If it's a single layer dvdrecorder you can only do a 1:1 backup on single layer dvds. The older DVD's often are single layer. But most if not all of the new dvds are dual layer to offer more bonuses and higher picture/sound quality.

You have to use transcoders like dvdshrink to fit a dual layer disc onto a single layer disc

But if you have a dual layer burner than it SHOULD be a bit for bit backup.

Kevin

[jimmalenko]

To get wayyyyyy too deep into theory, I don't think it will be a bit for bit copy, because DVDDecrypter is removing the CSS encryption on the VOBs. Now I would imagine that in order to store the CSS, this would take up some miniscule finite space and by using DVDDecrypter to remove this, we are in fact altering the total size of the DVD (if only minutely), unless DVDDecrypter still writes these bits, even with NULL data. The truth of the matter is that I don't know if DVDDecrypter does this or not, so I can only speculate. So to be mathematically acccurate, I don't think it's possible, bit for bit. From a practical point of view, DVDDecrypter turns a CSS-Encrypted DVD into an unencrypted DVD. As far as the actual video and data goes, it is completely untouched and follows Yoda's rules - DVD5 to DVD5 is a clone, as is DVD9 to DVD9. As far as playing the DVD goes, it IS an exact copy

[Cornucopia]

To clarify:

You all are mainly concerned with "User Data"

As to CD copying--

It is possible, but not always likely, to do a bit-for-bit copy of the 2 Audio channels and the P,Q, & R-W subcode. It's almost impossible, and not very desireable, to do a bit-for bit copy of the error detection and correction codes.

BTW, Audio tracks and (S)VCD Mpeg tracks have 2 levels of error detection/correction (which do take care of alot of types of errors). CD-ROM's and DVD's (of all flavors) have 3 levels.
The code on DVD is even more robust than the code on CD-ROM, so it's almost like saying it has 3 1/2 levels.

As to DVD copying--

Stamped/Pressed DVD's have a slightly different structure than DVD-R's, DVD-RW's, DVD+R's, DVD+RW's or DVD-RAM. For example, stamped DVD-ROM allows for a 2054 byte sector, whereas all the others allow for only 2048 bytes per sector. Guess what that extra sector area is reserved for? That's right---Encryption keys! That's one big reason why you can't do a bit-for-bit copy of encrypted discs.

Now, barring the encryption business, the User Data of a DVD-R or -RW can be bit-for-bit exactly like a DVD-5. And if they ever get off their butts and finalize the spec, DVD-R DL will be bit-for-bit exactly like DVD-9.
What about +R? Well, it can be if you don't have to use up the whole disc, as +R/W's have a few MB less available space than -R/W's and RAM(v2) discs.

Just like CD's, DVD's have area's of the disc that have error detection & correction codes, as well as other flags (including book type). Some of these are reserved/non-modifyable on recordable DVD's. So unless you have some industrial laser scan device and glass mastering plant, it's not practical to do a bit-for-bit of the whole disc structure. And for most of you guys' purposes, you don't need to.

Scott

[jimmalenko]

Thanks Scott - I didn't know how to explain the exact technical reasons why, but was somewhere near the ballpark