DVD Demystified

154
New Wine in Old Bottles: DVD on CD
Chapter 4
Another compatibility problem, which falls between application and implementation,
has to do with putting DVD content on media other than DVD.
Many people would like to be able to put short DVD-Video programs onto
CDs or inexpensive CD-Rs. The idea of a “mini-DVD” is very appealing, particularly
for testing titles during development and for viewing short programs
such as music video singles, home movies, or corporate marketing
clips. However, each would-be clever inventor is disappointed to learn that
it does not work on set-top players. Only a few odd player models designed
around DVD-ROM drives can play the discs. All other DVD-Video players
fail to play DVD-Video content from CD media. A number of reasons for this
are:
1. The player does not expect DVD content on CD media. The first thing
most players do after a disc is inserted is check focus depth and
reflectivity. If nothing can be read at DVD focus, the player switches
focus (and usually switches lens and laser as well) to see if it can read
data at CD focus depth. If it determines that a CD is in the drive, it
goes to CD mode. It checks for audio CD content, and it might check
for Video CD content or MP3 files, but it does not look for DVD files.
2. The drive unit is not fast enough. It is simpler and cheaper for players
to spin CDs at 1X speed rather than the 9X speed needed to provide
the 11 Mbps data rate required by DVD-Video content.
3. Many players cannot read CD-R discs. A player without a laser at CD
wavelength cannot read CD-R media.
Hollywood may be concerned about movies being copied easily and
cheaply to CD-Rs that would play in DVD players, although the quality
would be poor even if the video were spread across more than one CD. Of
course, player manufacturers could deal with all three of these obstacles,
but they do not believe that the demand justifies the extra expense. Some
also may accuse them of not wanting to sustain the CD market when they
can make more money (or pay fewer royalties) with DVD.
Computers are more forgiving. Most of them are media agnostic when it
comes to DVD content. DVD-Video files from any source with fast enough
data rates, including CD-R or CD-RW, or even hard drives or Jaz drives,