The first four forms of copy protection (Macrovision, CGMS,
CSS, and CPPM) are optional for the producer of a disc. CSS
decryption is optional for hardware and software playback manufacturers,
although a player or computer without decryption capability
will only be able to play unencrypted movies. CPRM is handled
automatically by DVD recorders, although it's optional and many
recorders don't support it. DTCP and HDCP are handled by DVD
players with digital video outputs.
These copy protection schemes are designed only to guard against
casual copying (which the studios claim causes billions of dollars
in lost revenue). The goal is to "keep the honest people
honest." The people who developed the copy protection standards
are the first to admit they can't stop well-equipped pirates.
Movie studios have promoted legislation making it illegal to
defeat DVD copy protection. The result is the World Intellectual
Property Organization (WIPO) Copyright Treaty and the WIPO Performances
and Phonograms Treaty (December 1996) and the compliant U.S.
Digital Millennium Copyright Act (DMCA), passed into law in
October 1998. Software intended specifically to circumvent copy
protection is now illegal in the U.S. and many other countries.
A co-chair of the legal group of the DVD copy protection committee
stated, "in the video context, the contemplated legislation
should also provide some specific assurances that certain reasonable
and customary home recording practices will be permitted, in
addition to providing penalties for circumvention." It's
not at all clear how this might be "permitted" by
a player or by studios that routinely set the "don't copy"
flag on all their discs.
DVD-ROM drives and computers, including DVD-ROM upgrade kits,
are required to support Macrovision, CGMS, and CSS. PC video
cards with TV outputs that don't support Macrovision will not
work with encrypted movies. Computers with IEEE 1394/FireWire
connections must support the final DCPS standard in order to
work with other DCPS devices. Likewise computers with HDMI (DVI)
connections must support HDCP to output DVD-Video content. Every
DVD-ROM drive must include CSS circuitry to establish a secure
connection to the decoder hardware or software in the computer,
although CSS can only be used on DVD-Video content. Of course,
since a DVD-ROM can hold any form of computer data, other encryption
schemes can be implemented. See 4.1 for more information on
DVD-ROM drives.
The Watermarking Review Panel (WaRP) --the successor to the
Data-Hiding Sub-Group (DHSG)-- of the CPTWG selected an audio
watermarking system that has been accepted by the DVD Forum
for DVD-Audio (see 1.12). The original seven video watermarking
proposals were merged into three: IBM/NEC, Hitachi/Pioneer/Sony,
and Macrovision/Digimarc/Philips. On February 17, 1999, the
first two groups combined to form the "Galaxy Group"
and merged their technologies into a single proposal. The second
group has dubbed their technology "Millennium." Watermarking
permanently marks each digital audio or video frame with noise
that is supposedly undetectable by human ears or eyes. Watermark
signatures can be recognized by playback and recording equipment
to prevent copying, even when the signal is transmitted via
digital or analog connections or is subjected to video processing.
Watermarking is not an encryption system, but rather a way to
identify whether a copy of a piece of video or audio is allowed
to be played. New players and software are required to support
watermarking, but the DVD Forum intends to make watermarked
discs compatible with existing players. Reports were made that
the early watermarking technique used by Divx caused visible
"raindrop" or "gunshot" patterns, but the
problem was apparently solved for later releases.
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