Hi.

I made some tries with how to "best" archive some of may aging DVDs.

First I found out that dd actually fails (with tons of block errors),...
quite a surprise since I thought CSS was not acting on the block but
rather on the file level.

After some tries I've noticed, that when playing the dvd before
with e.g. mplayer or something that uses libdvdcss/libdvdread dd/ddrescue
etc. work just fine[0].




I also stumbled over dvdbackup, so I wanted to compare the results of dd
with those of dvdbackup.

The first thing I've noticed is:
When I play to loopback device mounted dd image, it still does determine
the CSS keys, so that image apparently still uses encryption (which makes
me again not understand CSS) - any ideas?
When I play the --mirror copy from dvdbackup it doesn't do deCSS again.




Last but not least, the "bug" / improvement wishlisht:
When I use e.g. lsdvd -x on the actual DVD drive, it gives me a:
The same on the dd created image files, but it's lost on the dvdbackup -M
created files:
else which takes place at the UDF level is lost with how dvdbackup
backups (also including file dates, owners, etc.)


Another thing that's probably lost is some other title information:
When you run dvdbackup -I on the actual disc it shows:
The same when you run it on the dd created images, but this is gone
when you run it on the dvdbackup -M created files:

Not sure whether this "title" is also part of the UDF meta data,...
in any case - it seems to be "lost".


Another thing is, that dvdbackup "looses" any empty "AUDIO_TS" directory.


All these losses may not look like a disaster (and probably they aren't ;-) )
but for those perfectionists which want to make perfect copies it's bad.


My proposal would be, that one may perhaps add an --image mode, which creates
and UDF image, but initialises CSS before (so that one doesn' get these block
errors).


Cheers,
Chris.


[0] When doing subsequent dumps of the disc with dd, there is still always
one position with bit differences,... only a few bytes,... but I don't
understand why - any idea?

btw:
Further things that could theoretically be lost in a non-image mode are
files deleted and hidden in the UDF.

E.g. the kernel UDF driver can make these visible with the mount
options:
       unhide Show otherwise hidden files.

       undelete
              Show deleted files in lists.


I'm not aware that any Video DVD would have ever used this... or even
could make use of it (since I'd guess no hardware player could read
such files).
But at least theoretically such special files might be there and - for
all the archivists amongst us ;-) - a dd-like image mode would preserve
them.


Best wishes,
Chris.