From: Jonathan C. <Jon...@cr...> - 2003-08-11 22:55:32
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I am sorry, but I don't understand what I should do. I forgot to add to the original e-mail that just after I installed ALSA I could play DVDs and listen to them, then I think I installed the ALSA library or utilities or tools then it stopped working. Jonathan James Courtier-Dutton wrote: > Michael Roitzsch wrote: > >> Hi Bill, >> >> >>>> Encryption (aka CSS) and Region Codes are two different protection >>>> mechanisms. Encryption does not prevent you from reading the raw >>>> data. Of course you would read only garbage, but you should not get >>>> IO-Errors just because the disc is encrypted. >>> >>> >>> All I know is that I get the "Input/output error" messages when I >>> try to access the files on a mounted DVD, and my region is set to >>> region 1 (unless something unset it somehow) and I can play DVDs >>> fine. I have to first run the livid tstdvd command, which I >>> understood did some kind of ioctl to the DVD device to unlock the DVD >>> (and saves a disc-key file in the current directory), and only then >>> can I cat files from the mounted DVD. >> >> >> >> That's interesting. There is a third mechanism involved called "drive >> authentication". I guess the drive needs to be somehow initialized >> before it reads the region code from the disc and compares it to the >> internal value. So (my guess again) I think before authentication, >> you cannot read anything and after authentication you can read the >> VOBs if the region matches. Thanks a lot for putting me on to this. >> >> Michael >> > > Here is a summary of what should happen: - > > 1) Protected DVDs contain a table that tells the DVD-ROM hardware > which sectors are locked. The sectors are locks as soon as the DVD is > placed in the DVD drive. (This is what causes "Input/output error" in > linux) > > 2) An authentication step is done which then releases these sectors. > Windows 2000/XP does this authentication step as soon as you place the > DVD in the drive. Linux does not. > > 3) Key negiotiation occurs with a possibility of having a different > key for each VTS. (commonly called css) > > 4) Player reads sectors off the DVD and uses the key to decode them. > > Different DVD drives act differently. Some do step (1) and some do not. > Some check for DVD region at stage (2), some do not. > If the DVD hardware checks for DVD region at state (2), stage (3) is > then impossible no matter how good libdvdcss is. > If stage (3) fails, then users can still play DVDs, but libdvdcss > takes a lot longer cracking keys. > > Special note: - > If one has a RPC2 DVD-ROM hardware (not region free), but one has > never set the DVD region on the DVD-ROM hardware itself, it might > actually act as a RPC1 drive. (E.g. One of the DVD-ROM drives I have.) > BUT: If you ever install Windows, the region on the RPC2 DVD-ROM drive > will automatically be set without you being informed. This will then > cause the linux dvd players like xine to fail, because what used to be > a region free drive, is now a RPC2 drive. > > Cheers > James > > > |