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Re: DVD Double Layer Playing problem


Thank you very much for taking the time to reply.  Most of what you say
makes the trouble I am having make sense.  But three things do not seem
to fit:

1) I can play the .iso that I made with dd just fine in Xine.  This
should be just as scrambled as the DVD I burn from it.

2) This procedure has worked to create a copy of a commercial single
layer DVD just fine.

3) running diff on the .iso and the (unplayable) mounted burnt DL DVD
reported no differences.


On Tue, 2006-07-11 at 16:28 +0200, Andy Polyakov wrote:
> > I recently obtained a two DVD+-RW DL burners and decided to test them by
> > trying to burn a copy of Monster's Inc (which is a DVD we own that is a
> > DL disk)  They are the Plextor DVDR PX-750A  and the DVD-RW drive that
> > comes with the SONY VIAO VGN-SZ160P.
> > 
> > I used 
> > 
> > dd if=/dev/dvd of=DVD.iso bs=2048
> > 
> > to make the ISO, and
> > 
> > growisofs -dvd-compat -Z /dev/dvd=DVD.iso
> > 
> > to burn it.  
> > 
> > There were no reported errors at all during the burning process.
> > 
> > I can mount the burned disks on the either of the Dl DVD+-RW drives that
> > did burning, but my oldest DVD drive (which is only a DVD-RW single
> > layer burner) thinks there is no media there (it can play commerical DL
> > DVDs just fine).
> It's probably deficiency of this recorder. Recorders [unlike pure ROM 
> players] are expected to have closer look at media, closer than looking 
> at Media Book Type that is. It probably smells recordable media, but 
> it's too old to believe that it's double layer...
> >  I can play the ISO image with xine no problem and I
> > have used "diff" to verify that 
> > 
> > 1) The ISO and the burned DVDs movie are the same
> > 
> > But I cannot play the burned DVDs as video anywhere, including the
> > drives that burned it one (with either windows or linux)  On windows or
> > a commercial stand-alone DVD player I get a frozen scene from one of the
> > previews with a stuttering text that loops after a few minutes.  With
> > either xine or totem it reports that this DVD is encrypted and
> > recommends that I install libdvdcss.  I have libdvdccs installed and it
> > is what I use to watch most commercial DVDs that I watch.
> Content protection is two-fold. First you have to authenticate yourself 
> to unit so that it gives up protected sectors, and then you have to 
> descramble the content. When you ran dd you probably were authenticated 
> [you probably ran xine prior dd], but dd doesn't do any descrambling and 
> therefore you've copied scrambled content. When you burn it to 
> recordable media it turns unplayable [you're likely to hear audio 
> though], because you didn't copy the descrambling keys, nor marked 
> protected sectors as scrambled. But before you ask how do you do the 
> latter two, keep in mind that you *can't*. Consumer recordables provide 
> *no* way to copy or setup own descrambling keys and therefore the only 
> way is to descramble content prior recording. How is another question 
> [which I don't feel capable to answer].
> > It seems clear that in terms of data and filesystems,
> I'd challenge the "terms of data" part. The fact that you can mount it 
> is not mystery, because not everything is scrambled. Most notably 
> sectors describing/defining file system layout are not, which is why 
> it's never a problem to mount protected media and list files on it. Not 
> even whole video content is scrambled, most notably menus are commonly 
> not, so you can always "navigate"... A.
"Choosing a basis for a vector space is an act of violence"
--unkown University of Chicago professor circa 1989
(If you know who said this please let me know)

Brett Stevens
School of Mathematics and Statistics
Carleton University
1125 Colonel By Dr.
Ottawa ON K1S 5B6 Canada
613 520 2600 x2125

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