[linux-elitists] regarding DVD's

Seth David Schoen schoen@loyalty.org
Wed Jan 26 19:52:33 PST 2000


ben@valinux.com writes:

> You know something just dawned on me. Do you realize that the thing
> that has made it essentially impossible to pirate DVD's is NOT CSS but
> rather the fact that the data is already compressed.

Depends what you mean by "pirate DVDs".

You seem to be talking about piracy by adapting formats and then sharing
data e.g. over the net.  There are other possibilities using physical
media...

> See the thing that makes CD's so easy to copy is the fact that you can 
> take the data off of a CD and turn it into a much smaller mp3. A mp3
> is still pretty big but it is small enough that you can still move it
> around without too much trouble.

With CDs, you can also do an exact byte-for-byte copy onto CD-R.  Part
of the CSS ensemble, as I now think I understand it, makes _that_
impossible:

http://www.loyalty.org/~schoen/dvdtable.html

Another consequence is that you can't _read_ the video data from a DVD
in a form that you can use (unless you can break CSS).

> With DVD's the data is so large and there is little hope of
> compressing it further and so it will have to wait several generations 
> of technology before it is even feasable to copy or move around rather 
> than just one or two generations.

For byte-for-byte copies, the technology is already available; it's
just that consumers aren't supposed to be able to buy media which will
work for doing byte-for-byte copies without breaking CSS.

For format conversions, if you can get the raw video stream, you can
still always downsample it into some form that fits your requirements.
An example that came up on the decss list is ripping DVD to VCD.  Now,
VCD video data is lower quality than DVD video data, as far as I know.
But if you can break CSS, then you can downsample the video stream to
VCD quality, re-encode it, and write it to VCD.

Since blank CD-Rs are inexpensive, this is a meaningful possibility.

It should be noted that you probably have a legal right to convert a
DVD you own to VCD for personal use, if you don't distribute it, under
US copyright law.  The strange paradox is that you may or may not have a
legal right to take all of the individual steps necessary to accomplish
this. :-)

-- 
Seth David Schoen <schoen@loyalty.org>  | And do not say, I will study when I
Temp.  http://www.loyalty.org/~schoen/  | have leisure; for perhaps you will
down:  http://www.loyalty.org/   (CAF)  | not have leisure.  -- Pirke Avot 2:5




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