Re: Ripping DVDs ... and MythTV

["Derek Martin-9" <user=7@nabble.blu.org>]

 On Wed, Nov 21, 2007 at 11:43:44PM -0500, Kristian Erik Hermansen wrote: 
> Naw dude, the DVD drive hardware locks the disc content until your 
> software goes through an authentication process with the physical 
> drive firmware.  This is the very first thing libdvdread does when it 
> opens a CSS-encrypted video DVD for reading.  It goes through the 
> authentication process in order for the data to be available.  Jarod, 
> you have probably never seen the problem before because you have 
> always run a system which already has the libdvdread package installed 
> :-)   

dd is not linked against libdvdread: 

$ ldd `which dd` 
        linux-gate.so.1 =>  (0x00110000) 
        librt.so.1 => /lib/librt.so.1 (0x00b19000) 
        libc.so.6 => /lib/libc.so.6 (0x00702000) 
        libpthread.so.0 => /lib/libpthread.so.0 (0x0088f000) 
        /lib/ld-linux.so.2 (0x006df000) 

This means that when you use dd to copy a DVD, libdvdread is never 
given a chance to come into play.  It just works because it's copying 
raw bits off the DVD, which has to be possible, or else it would be 
impossible to decrypt the data on the drive (the keys are on the 
disc).  This is was well understood when Johansen created dvdcss: he 
made the point that it was always possible to copy DVDs, and that his 
software was only useful for actually making them playable on Free 
OSes. 

The key is that CSS considers the "disc content" to be the movie, 
rather than the raw bits.  So yes, authentication needs to happen 
before you can play the movie.  It doesn't need to happen before you 
can read the raw bits. 

Red Hat 6 might not copy DVDs, but if so only because hardware support 
for DVD drives didn't exist when it was released. 

-- 
Derek D. Martin    http://www.pizzashack.org/   GPG Key ID: 0xDFBEAD02 
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