On 12Sep2018 17:40, JD <jd1008@xxxxxxxxx> wrote:
On 09/12/2018 04:39 PM, Cameron Simpson wrote:
On 13Sep2018 08:29, Cameron Simpson <cs@xxxxxxxxxx> wrote:
Regarding the DVD CSS stuff: I seem to recall from long ago that
reading a CSS DVD without the libdvdcss stuff to arrange decoding
produced read issues, not just garbled data. This might be that.
Ah, here we go. In the tar-1.30 source, src/create.c, around line
1104. The "shrank...padding" message happens if tar gets a short
read (not an I/O error).
So I think the VOB file read is very short. See if other tools can
read that file, since it is a mounted drive.
Cheers,
Cameron Simpson <cs@xxxxxxxxxx>
I tried that, and it is clear that tar is unable to read the drive. To wit:
$ ls -l VTS_10_1.VOB
-r--------. 1 jd jd 1073739776 Mar 18 2013 VTS_10_1.VOB
$ cat VTS_10_1.VOB | wc -c
cat: /run/media/jd/JACK_REACHER/VIDEO_TS/VTS_10_1.VOB: Input/output error
4067328
So, the output file was padded by zeros instead of the real McCoys!!!
In other words, dvdcss screwed up royally, and I cannot use the backup
as replacement if my DVD gets seriously damaged by a bad player drive.
Just wonderbar!!!!
I am suggesting that dvdcss is not involved in a DVD _mount_, so no decryption
occurs. Instead, I/O errors occur - you don't get encrypted VOB data, you get
no data.
Making an undecrypted backup of a CSS encrypted DVD is of little value without
a tool to use the encrypted data or away to burn a usable Video DVD from your
backup (players won't use an encrypted video anyway).
Mounting an unencrypted DVD isn't an issue, but commercial Video DVDs are
encrypted so unless the mount command contrived some decryption, tar or any
other CSS unaware tool isn't going to do you any good.
You are encountering all the pleasures of DRM, which is why we all hate it.
Backups are just one facet of the problem.
I speak as one with quite a few DVDs I'd like to make soft copies of. Not to
reburn working like-the-original DVDs again (because my hatred of most DVD menu
designs is like a searing flame) but to be able to watch them without having to
dig around a bookshelf, etc etc.
One day I need to spent a lot of time with handbrake or similar to get good MP4
rips of their video with decent metadata and filenames. Did I say "day"? Not
nearly long enough.
Cheers,
Cameron Simpson <cs@xxxxxxxxxx>
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