[Liverpool] Backing up video DVD's

[Sebastian Arcus]

Following on from the conversation the other night regarding backing up 
video dvd's, I went back and did more experiments.

1. cp and dd will work on dvd's without copy protection.
2. dd will work on some copy protected dvd's - if used with "bs=1024" as 
an option.
3. However, both cp and dd will fail (sometimes after about apparently 
random amounts of data - on some dvd's as much as 298MB) on dvd's with 
certain copy protection systems. The failure is different from film to 
film, but the amount of data copied before failure is always the same on 
different tries for the same disc. In my case only about 25% of dvd 
discs I tried could be copied with dd or cp.
4. vobcopy will manage most copy protection systems - but I still have 
about 1% of my brand new dvd's which have played just fine on the same 
computer - but vobcopy hasn't managed to copy. I've seen other reports 
on the internet that there are several copy protection types which give 
problems even to vobcopy. Maybe it will be fixed in a future version. 
The symptom seems to be caused by a trick in the layout, where the drive 
is stuck in what sounds like repeated seek action on the disc - in a 
permanent limbo - while copying under vobcopy.

I'm using vobcopy 1.2.0. I'm not sure how would one find out which copy 
protection system a particular dvd is using. I've seen talk on the 
Internet about several different types - but nobody mentioned how to 
find out what is used on a particular disc.

I would be curious if others have found otherwise on their machines or 
their dvd's

Sebastian