Re: [gentoo-user] DVD Movie backups

[Mark Knecht <markknecht@gmail.com>]

On Fri, Dec 16, 2011 at 9:53 AM, Michael Mol <mikemol@gmail.com> wrote:
> On Fri, Dec 16, 2011 at 12:25 PM, Mark Knecht <markknecht@gmail.com> wrote:
>> On Fri, Dec 16, 2011 at 9:06 AM, Michael Mol <mikemol@gmail.com> wrote:
>>> No; you'll have to decrypt, or do without the encrypted bits.
>>>
>>> dvdbackup is probably the closest to what you want.
>>>
>>> On Dec 16, 2011 11:09 AM, "Mark Knecht" <markknecht@gmail.com> wrote:
>>>>
>>>> For archive purposes is there a simple way for me to make a
>>>> bit-for-bit copy retail DVDs I've purchased?
>>>>
>>>> Assume that I've got the right sort of DVD drive, I guess something
>>>> capable of writing dual-layer DVDs.
>>>>
>>>> Thanks,
>>>> Mark
>>
>> Interesting. So even something that just copies blocks of data, like
>> dd, can't be used for that purpose?
>>
>> I have no interest in tearing apart the DVD in any way. It was more
>> about the idea of a fire causing the loss of maybe $15K-$20K
>> investment over the years. I can rip all the CDs, keep the ripped
>> version here to watch on the computer, and store the DVDs elsewhere,
>> but that elimiates (generally) being able to watch special features
>> which my wife and kid enjoy.
>>
>> Thanks for the info.
>
> I did exactly the same thing a few years ago, but it's been a long,
> long time, so my memory on my process is very fuzzy. (It also involved
> my first foray into RAID...I've got a couple hundred DVDs!) Go ahead,
> count the number of times I qualify something with "IIRC"...
>
> dvdbackup can recreate the ISO images, IIRC.
>
> If you run a simple 'dd' on a DVD with encrypted portions, you'll get
> I/O errors when it encounters the encrypted pieces. IIRC, some of the
> data required to decrypt those portions is on the disc, but it's in an
> out-of-the-way portion that won't show up as part of the block device.
> IIRC, dvdbackup makes use of libdvdcss to decrypt the encrypted
> portions[1], and writes a decrypted version of the data. *this* is why
> you can't make a bit-for-bit copy; the output data would be decrypted.
>
> There are other, later obstacles, too; once CSS was broken, some
> content publishers (Bandai USA, for example) would fudge the ISO spec
> and the DVD nav specs in ways that didn't break *most* hardware DVD
> players, but did tend to break players which strictly adhered to the
> standards, such as ffmpeg, vlc and mplayer. It also broke dvdbackup
> for me, IIRC, which is why I had to resort to vobcopy in some cases. I
> expect the software angle for handling these things has gotten better,
> though.
>
> [1] I don't know how it does it when dd would have hit an I/O error.
> Obviously, my understanding of the workings of dvdbackup, dd, DVDs and
> CSS encryption is flawed somehow.
>
> --
> :wq
>

Thanks for the info. It makes it a bit clearer as to what's causing
the road block vs. the sort of answer Jorg provided this morning which
did nothing (as when I asked on the cd-record list a few days ago and
the answer there did nothing either) to advance my knowledge on the
subject.

I appreciate the time it took you to respond. Thanks!

Cheers,
Mark