[mythtv-users] Ripped DVD recordings have skips
jarpublic at gmail.com
Thu Apr 9 16:27:48 UTC 2009
> Yes, but the question is whether the writable dual-layer discs have the
> same capacity as the pressed versions. My understanding is that they do
> not, but that's just from a vague recollection of something I read a
> long while ago.
Check http://en.wikipedia.org/wiki/DVD#DVD_capacity. Most pressed DVDs
are single sided and dual layered (aka DVD-9). Both types of dual
layered recordable DVD have the same or more capacity.
>> Usually you can just skip the crap they add on to the movies, it's an unusual
>> movie that is over 2 hours.
> Yes, but then you're not doing an exact copy, and have to deal with the
> copy-protection during the ripping. The whole point of this part of the
> thread was that the copy-protection issue could be avoided during the
> back-up process by doing a bit-level copy. This would avoid DMCA issues
> when backing up legally purchased DVDs (though if there's a capacity
> difference between recordable & pressed discs, the backup copy won't
> necessarily do you any good anyway).
Even if you are doing a bit level copy I believe it is possible to
only copy the portion of the disc that has data. Most DVDs don't use
the full disc. It would either need to be a really long movie at high
bitrates, or the DVD needs to be filled with a lot of extra junk.
I think you may be able to make a bit-level copy with something like
ddrescue, but dd would choke on the bad sectors. It would keep trying
to read them over and over again, taking hours or days to finish.
Ddrescue uses dd but is more robust with regard to bad sectors and
allows you to control how to handle them. The main copy protection
that introduces the bad sectors is called ARccOS (you can thank Sony
for this one). However, I believe that there are more complex copy
protection mechanisms that take advantage of various idiosyncrasies
between the way a player handles a DVD and he way a computer will read
the disc. If this weren't the case it wouldn't be necessary for
Slysoft to be updating their software every few months to deal with
the latest batch of hacks.
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