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From dmh@jet.es Wed, 18 Aug 1999 14:22:53 +0200
Date: Wed, 18 Aug 1999 14:22:53 +0200
From: David MH dmh@jet.es
Subject: [Livid-dev] uh? no ripping? who said that?

Hi, first of all i must say hello as i am new to this list. I don't even =
have a dvd drive, but i am
very interested in whatever may appear from the livid project.

I have been reading some posts of the archived mailing list, and someone =
said that CSS prevented
from ripping dvd movies to disk... I know of at least 2 programs that all=
ow to do that, their names
are PowerRipper and DVD Rip, evidently, as i don't have a dvd drive, i do=
n't know how do they do
that, and if they do or not real ripping from the movies. AFAIK, PowerRip=
per outputs .avi files
while dvd rip outputs to some less known file format. I don't even know i=
f that programs are
supported/made by a legal company (i don't think so) or who wrote them.

As my knowledge about dvd internals is pretty low, i would like to make s=
ome questions.

As i understand, DVD titles can be played (mmm, the format understand i =
mean) because of
the CSS code, am i right? I understand that the drive uses CSS (in encryp=
ted DVD's) and unless the
player uses CSS also, the drive won't play the disc... Is that right??
So in theory, and unencrypted disk could be played using an mpeg2 player=
, right??
And CSS does not really encrypts the disc, it just "protects" the data f=
rom being accesed
using a non-css compliant software, right?


Going to other post about using overlay hardware to display video, you sh=
ould check the bt848/878
equiped tv-tuner/capture cards, they are really cheap, and work perfectly=
under linux as the chips
specs are freely avaliable. They are able to work overlaying the image (v=
ia the PCI bus, no
external cable) or by grabbing the image from the BT card and "putting it=
" manually in the video
card (MUCH slower). They usually came (mine at least, a Miro PCTV) with a=
n antenne input, Composite
Video input, and S-VHS input, as well as an audio output (internal and ex=
ternal) to connect it to a
soundcard. (btw, brooktree makes that chips)

Thanks for your time
David MH


--------------------------------------------------
Physics - Universidad Aut=F3noma de Madrid (www.uam.es)
Powered by LinuX 2.2.11
Enlightenment 0.16 CVS

From pvolcko@concentric.net Wed, 18 Aug 1999 09:14:37 -0400 (EDT)
Date: Wed, 18 Aug 1999 09:14:37 -0400 (EDT)
From: pvolcko@concentric.net pvolcko@concentric.net
Subject: [Livid-dev] uh? no ripping? who said that?

> I have been reading some posts of the archived mailing list, and someone 
> said that CSS prevented
> from ripping dvd movies to disk... I know of at least 2 programs that 
> allow to do that, their names
> are PowerRipper and DVD Rip, evidently, as i don't have a dvd drive, i 
> don't know how do they do
> that, and if they do or not real ripping from the movies. AFAIK, 
> PowerRipper outputs .avi files
> while dvd rip outputs to some less known file format. I don't even know 
> if that programs are
> supported/made by a legal company (i don't think so) or who wrote them.

To my knowledge these programs don't take data from disk or otherwise
circumvent CSS. What they do it take the data heading to the display and
re-encode it into another format, such as AVI or MPEG1. The data is
different than that on the disc and it tends to be of lower quality (I
think, I don't knwo for sure). 

> As my knowledge about dvd internals is pretty low, i would like to make 
> some questions.
> 
> As i understand, DVD titles can be played (mmm, the format understand 
> i mean) because of
> the CSS code, am i right? I understand that the drive uses CSS (in 
> encrypted DVD's) and unless the
> player uses CSS also, the drive won't play the disc... Is that right??
> So in theory, and unencrypted disk could be played using an mpeg2 
> player, right??
> And CSS does not really encrypts the disc, it just "protects" the data 
from being accesed
> using a non-css compliant software, right?

CSS has two parts, disc sector blocking and data encryption. The first
part, sector blocking, prevents scrambled sectors from even being read (in
scrambled form) from the disc unless an authentication has occured and
passed. This is why it ispossible to read the video_ts.ifo and
video_ts.vob files (and sometimes the vts_01_0.ifo file as well) but not
the other data files (read errors usually occur). The second part,
encryption, is what protects the VOB data on disc from being intercepted
between drive and decoder. The data is actually encrypted on disc and it
is transfered from drive to decoder in that form. The decoder has to have
CSS decryption ability to be able to play the data.

You are right, however, that unencrypted DVDs can be played (for the most
part) on standard mpeg2 software decoders. You won't be getting any of
the features of DVD-Video such as interactive menus, angle changing, and
subpciture/sub-titles, and you won't be getting sound out of it (assuming
AC-3 encoding), but you will see the raw mpeg-2 video stream displayed.


Hope this helped. And welcome to the list. Do you intend on getting a
dvd drive pretty soon? What about a DVD Decoder card, or are you wanting
software decoding instead?

Paul Volcko
LSDVD

From dmh@jet.es Wed, 18 Aug 1999 15:36:57 +0200
Date: Wed, 18 Aug 1999 15:36:57 +0200
From: David MH dmh@jet.es
Subject: [Livid-dev] uh? no ripping? who said that?

> To my knowledge these programs don't take data from disk or otherwise
> circumvent CSS. What they do it take the data heading to the display a=
nd
> re-encode it into another format, such as AVI or MPEG1. The data is
> different than that on the disc and it tends to be of lower quality (I
> think, I don't knwo for sure). =20
That makes sense...It seemed strange for me that an "appeared from the du=
st" software could have
accomplished what seems to be big effort task.

> CSS has two parts, disc sector blocking and data encryption. The first
> part, sector blocking, prevents scrambled sectors from even being read =
(in
> scrambled form) from the disc unless an authentication has occured and
> passed. This is why it ispossible to read the video_ts.ifo and
> video_ts.vob files (and sometimes the vts_01_0.ifo file as well) but no=
t
> the other data files (read errors usually occur). The second part,
> encryption, is what protects the VOB data on disc from being intercepte=
d
> between drive and decoder. The data is actually encrypted on disc and =
it
> is transfered from drive to decoder in that form. The decoder has to h=
ave
> CSS decryption ability to be able to play the data.
>=20
> You are right, however, that unencrypted DVDs can be played (for the mo=
st
> part) on standard mpeg2 software decoders. You won't be getting any of
> the features of DVD-Video such as interactive menus, angle changing, an=
d
> subpciture/sub-titles, and you won't be getting sound out of it (assumi=
ng
> AC-3 encoding), but you will see the raw mpeg-2 video stream displayed.
Yeah, thats ok, i said an mpeg2 player. of course everything that is not =
mpeg2 won't be displayed
(and from i have read, it will distort the mpeg2 stream because the mpeg2=
player get confused). =20
> Hope this helped. And welcome to the list. Do you intend on getting a
> dvd drive pretty soon? What about a DVD Decoder card, or are you wanti=
ng
> software decoding instead?

yes, that's the idea, as my cdrom drive is... let's see, venerable... (ar=
gh! old :P), i plan to go
with software decoding, my new p3-450 with 256 meg of ram should be enoug=
h to do that.
Going for a hardware solution now that probably won't be ever supported i=
n linux would be imho a
vert stupid action for me. I always check if the hardware i'm buying is s=
upported in linux.
Any recomendations/"brands-to-avoid" for dvd drives???


Regarding CSS, the CSS algortihm is in the dvd 5$k specs, isn't it?? and =
of course if someone bys
the spec and reveal (or publish source code from) the CSS it would be in =
BIG legal troubles i think.
And appart from a "css-hardware-done" solution", is there any kind of sol=
ution possible to have an
opensource dvd player??? (<DREAM MODE ON> other than if "someone" get his=
dvd specs "strangely"
stolen... and "someone" find them and... "incredibily" the 2nd someone re=
leases the CSS specs to
this group.... </DREAM MODE OFF>)

David MH
------------------------------------------------------
Physics - Universidad Aut=F3noma de Madrid (www.uam.es)
Powered by LinuX 2.2.11
Enlightenment 0.16 CVS

From pvolcko@concentric.net Wed, 18 Aug 1999 10:23:47 -0400 (EDT)
Date: Wed, 18 Aug 1999 10:23:47 -0400 (EDT)
From: pvolcko@concentric.net pvolcko@concentric.net
Subject: [Livid-dev] uh? no ripping? who said that?

> yes, that's the idea, as my cdrom drive is... let's see, venerable... 
> (argh! old :P), i plan to go
> with software decoding, my new p3-450 with 256 meg of ram should be 
> enough to do that.
> Going for a hardware solution now that probably won't be ever supported 
> in linux would be imho a
> vert stupid action for me. I always check if the hardware i'm buying is 
> supported in linux.
> Any recomendations/"brands-to-avoid" for dvd drives???

Well, actually the way things are looking from legal, technical, and a
financial standpoint, it is looking more like software decoding on linux
is a ways off. The reason is that software decoding depends on sending
the unencrypted data to memory and since linux OS code is freely available
and modifyable one could modify it to take those unencrypted blocks and
send them elsewhere besides the video display routines (or audio or
whatever else). In this way CSS is circumventable under the linux os when
software decoding is used. Whether or not this is a strong and valid
argument or not is irrelevant. this is what software decoding based
vendors are thinking and it why there is very little action on that end of
the industry to get their programs on linux. 

That all said, hardware based decoding avoids all of that. As long as the
hardware solution either decodes adn displays via passthrough (sigma
design's method) or via direct hardware connection to the video board
(Matrox G200 daughtboard method) then CSS isn't circumventable.
This assumes decrypted blocks can't be read off the card in any way, which
is a safe bet considering CSS restrictions on the matter.

> Regarding CSS, the CSS algortihm is in the dvd 5$k specs, isn't it?? and 
> of course if someone bys
> the spec and reveal (or publish source code from) the CSS it would be in 
> BIG legal troubles i think.
> And appart from a "css-hardware-done" solution", is there any kind of 
> solution possible to have an
> opensource dvd player??? (<DREAM MODE ON> other than if "someone" get 
> his dvd specs "strangely"
> stolen... and "someone" find them and... "incredibily" the 2nd someone 
> releases the CSS specs to
> this group.... </DREAM MODE OFF>)

No the CSS specs are not part of the DVD-Specs, they are licensed
seperately through Matsushita (at least for the Americas, not sure about
other regions).

As for the open source DVD player, this is unlikely due to the NDA
DVD-Specs are released under. Portions could be opne sourced, for example
the GUI code could be and application logic (not DVD logic). If someone
did this then the dvd logic and decoder interaction logic would have to be
distributed in binary object form (to be legal, assuming they created this
"by the book"). This would allow "skins" for the GUI and freely available
applicaiton control logic, but whoever did this would be "eating" the cost
of getting the DVD-Specs.

Paul Volcko
LSDVD

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