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2-4-5] ...on an audio CD (Midbar Tech - Cactus Data Shield)




Description

This article is from the CD-Recordable FAQ, by Andy McFadden (fadden@fadden.com) with numerous contributions by others.

2-4-5] ...on an audio CD (Midbar Tech - Cactus Data Shield)

(2002/02/13)

Midbar Tech Ltd (http://www.midbartech.com/) appears to have two different
schemes under the "Cactus Data Shield" brand. (The web site shows three
now: CDS100, CDS200, and CDS300.) The first uses a non-standard TOC.
The position of the lead-out and the length of the last track were
tweaked, resulting in a disc that appears to be only 28 seconds long.
The alterations didn't confuse all CD-ROM drives, and it has been reported
that some Philips CD players couldn't play the discs. BMG Entertainment
reportedly tried it and abandoned it.

In late 2001, Midbar Tech announced a different approach. A US patent
(http://www.delphion.com/details?&pn=US06208598__) describes the invention.

The approach appears to involve inserting frames of bogus control information
into a relatively constant part of the CD audio stream. During playback,
the extra frames are skipped. A disc copy or digital stream on an S/PDIF
output will include the bogus frames, and when written to CD-R the extra
control information won't be included. The result is bad samples that only
appear in copies.

News articles:

- http://news.com.com/2100-1023-835841.html
- http://www.newscientist.com/news/news.jsp?id=ns99991105
- http://www.cnn.com/2001/TECH/ptech/08/08/cd.copy.protection.reut/index.html

The difficulty in copying such a disc depends on how the stream of audio
samples appears. In news articles the company claims that the scheme
can defeat method #2 described in section (2-4-3), in which the S/PDIF
connector of a CD player is used to get an error-interpolated digital
stream. That suggests that the bogus data doesn't appear as uncorrected
data, but rather as valid data that is suppressed on the analog outputs.
This would seem to make digital copying difficult, but it would also make
any form of digital playback impossible.

No specific disc titles have been announced, but Sony has reportedly
released a few titles in eastern Europe that use this.


Some personal notes on the early version (CDS100?) of the Cactus Data
Shield: I bought a copy of _My Private War_, by Phillip Boa & The Voodoo
Club, from an online retailer. The disc is labeled "Kopiergeschützte CD -
nicht am pc abspielbar" which translates literally to "copy-protected CD
- not at the PC playable". Supposedly this is one of the BMG discs that
was protected with Midbar's first product.

The Plextor Plextools utility saw it as a single-session audio CD with
13 tracks, but when I asked it to play the disc it only saw the first
28 seconds of the first track, and stopped after playing just that much.
My Panasonic CD "boom box" also thought the disc was only 28 seconds long,
but it happily played past that point, and would let me select any track.

The page at http://uk.eurorights.org/issues/cd/docs/natimb.shtml has an
analysis of the CD _White Lilies Island_ by Natalie Imbruglia.

http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=Cactus%20Data%20Shield%20200&index=0
has a very thorough examination of a CDS200 disc. Recommended reading.


 

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