[libdvdcss-devel] cache: use libxdg-basedir and save cache into XDG-compliant location.

Wed Feb 27 13:21:42 CET 2013

Hi,

I am new to this list. I expect that some members already know me from
other places.

On 27 Feb, Diego Elio Pettenò wrote :
> Is it the case? I never set the region of DVD drives and they seem to
> work just fine... including external USB drives.. I think most
> manufacturers pre-set the region on the units they sell.
* Jean-Baptiste Kempf <jb at videolan.org>, on 27-02-13, replied:
> I know that some don't, actually.

I confirm that.
My drive has a RPC type II, and the region is not set.
It was like that when I bought the computer (ASRock).

I am not an expert on the coding libdvdcss, so I hesitated discussing
on this list. Please tell me if I am inappropriate.

However, I do have much experience using it, since I own a pretty
large collection of DVD which I watch on my computer. I also got
interested in the working of libdvdcss, since I occasionnaly encounter
problèms. But reading the code and understanding it is another matter.

Using my drive, with no region set, I found that about 25 to 30% of
the DVDs have a title that cannot be found by libdvdcss (though I am
not sure whether the region setting of the drive has a responsibility
in this). I guess it does not matter for most people, as these titles,
often (but not always) very short, are generally not part of the main
film. Actually, for many of them, I wonder whether they contain any
information at all (none that I could identify with a player or with
avidemux). But again, I have much to learn.

On 27/02/2013 08:19, Reimar Döffinger wrote:
> There are also cases where titles are too short for cracking and thus
> only manually created key files work (which btw. speaks against the
> binary format, also look at e.g. libaacs, they too use text format
> files).

* Diego Elio Pettenò <flameeyes at flameeyes.eu>, on 27-02-13, replied:
> Manually created how? If there is a way to "manually create" a key for
> short titles, maybe it's a good idea to just fix libdvdcss so that it
> can generate he same?

* Jean-Baptiste Kempf <jb at videolan.org>, on 27-02-13, replied:
> Some people actually use that in dvdcss?

I do.

Actually, I often managed to get the correct keys by other means, and
added them by hand in the cache. I confirm it is easier in text format.

This lead me to get interested in the patterns of use of CSS keys
which is probably an interesting glimpse of industrial sociology (or
some similar 'science'). I am toying with the idea of systematic
statistics on this topic.

However, I encounter a variety of problems, and not knowing enough
about libdvdcss (I found very little documentation on CSS itself) I am
not sure what is the best approach to some of the problems. I would
appreciate if some of the experts on this list could answer some
questions, even though I am not a contributor to the actual libdvdcss
code.

My first question is the following. Given a title and a CSS key, is
there a reliable way (other than viewing, which is not always
adequate) to check that it is the proper key to decode that title.  My
experience is that some titles will be 'decoded' (?) without fuss by
many keys, and the bad keys will produce garbage without any
noticeable protest from the decoding software (libdvdcss, not always
within VLC).

I once had a key that decoded the title, but only for the upper half of
the screen.

Another question is the following. Given a coded title and a decoded
one. Is it possible to check that the first is an encoded version of
the second. Is it possible to identify more easily the key ? Can that
be somewhat easier than finding the key with only the encoded version
of the title.  I have met that situation in practice.

My last question concerns my DVD player.  I do not wish to change
the (absent) region setting, as I have DVDs from several different
regions (some films are just not published in region 2).  Would
libdvdcss be able to discover more keys if the player were set to the
region corresponding to the DVD.

Thank you for reading

Bien cordialement

Bernard

* Jean-Baptiste Kempf <jb at videolan.org>, le 27-02-13, a écrit:
> On 27 Feb, Diego Elio Pettenò wrote :
> > Is it the case? I never set the region of DVD drives and they seem to
> > work just fine... including external USB drives.. I think most
> > manufacturers pre-set the region on the units they sell.
> 
> I know that some don't, actually.
> 
> Best regards,
> 
> -- 
> Jean-Baptiste Kempf
> http://www.jbkempf.com/ - +33 672 704 734
> Sent from my Electronic Device
> _______________________________________________
> libdvdcss-devel mailing list
> libdvdcss-devel at videolan.org
> http://mailman.videolan.org/listinfo/libdvdcss-devel

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