playing iso from disk?

[Kristian Hermansen]

On 3/17/07, Robert La Ferla <robertlaferla at comcast.net> wrote:
> Why is that?  Isn't dd doing a raw copy and isn't it up to the player
> to decode it (assuming it has the proper decss)?

No.  dd will not be able to access encrypted sectors of the DVD.  You
can try if you want :-)  Here's a small doc on backing up DVDs that
mentions this:
http://gentoo-wiki.com/HOWTO_Backup_a_DVD#dd

I don't really know enough about the internals, but I suppose the key
unlocks the sectors at the firmware level.  Ask "DVD Jon" if you
really want to know.

When you say "RAW", no, dd does not do this.  dd just reads the
standard 2048 user-accessible sector length.  Tools that do "RAW"
copying usually return all P-W subcodes and ECC data.  This is
actually about 2500 bytes.  I am not aware of a Linux utility which
does this, but back in the day we utilized tools on Windows.  Now you
can use Alcohol 120, BlindRead/BlindWrite, CloneCD, etc.

Copying such data has become an "art" actually, because most consumer
video games for the PC implement very intelligent copy protection
mechanisms.  For instance, a game CD will be purposefully corrupted in
a very specific way during mastering.  Sometimes these corrupted
sectors are "weak", meaning that the pits/lands on the disc are not
the standard depth, and are thus harder to read for the laser.  If you
try to copy this, your reader will try until it determines what the
data is.  It may take a long time to read all weak sectors on the
disc.  However, when you burn this data to a CD-R (or use an ISO
image), the game will not function properly.  The reason is that the
game application will knowingly probe these sectors, and if the disc
immediately returns the correct data, it will determine it to be a
fake copy, since an original mastered copy will take much longer to
return the "weak" sectors.  Anyways, this is off on a tangent.  The
answer is no, dd does not return RAW sectors...
--
Kristian Hermansen

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