Chapter 1

78 Everything You Ever Wanted to Know About DVD
because the track spirals go in opposite directions (unless all four layers are
used). The DVD spec would have to be changed to allow reverse spirals on
layer 0. Even then, keeping both sides in sync, especially with MPEG-2’s
variable bit rate, would require independently tracking heads, precise track
and pit spacing, and a larger, more sophisticated track buffer. Another
option would be to use two heads to read both layers of one side simultaneously.
This is technically feasible but has no advantage over reading one
layer twice as fast, which is simpler and cheaper. (Refer to “Do DVDs Support
HDTV (DTV)? Will HDTV Make DVDs Obsolete?” for more information
about HDTV and DVDs.)
What Effect Will Fluorescent Multilayer
Disc (FMD) Have on DVD?
Very little, as Constellation 3D ran out of money in mid-2002. The various
reports of fluorescent multilayer disc (FMD) causing the early death of DVD
were wildly exaggerated and not founded in reality.
Fluorescent multilayer technology, which can be used in cards or discs,
aims a laser at fluorescent dye, causing it to emit light. Because it doesn’t
depend on reflected laser light, it’s possible to create many data layers
(C3D prototyped 50 layers in its lab). It can use the same 650-nanometer
laser as DVDs, so FMD drives could be made to read DVDs. In June of
2000, C3D announced a program to make FMDs with 25 GB per side that
would be readable by DVD drives with a “minor and inexpensive modification.”
C3D later said players would be available by mid-2001.
FMD was very cool technology, but it was new, with no track record,
developed by one small company. DVD is based on decades of optical
storage technology development by dozens of companies. The monumental
task of changing entire production infrastructures over to a new format
was too much for C3D, even with tens of millions of dollars and some large
partners.
How Does MPEG-4 Affect DVD?
MPEG-4 is a video encoding standard designed primarily for low-data rate
streaming video, although it’s actually more efficient than MPEG-2 at DVD
and HDTV data rates. MPEG-4 provides for advanced multimedia with
media objects, but most implementations only support simple video (Simple
Visual Profile). MPEG-4 part 10, also known as H.264 (and also known
as JVT or AVC) is an even better encoding standard.
DVDs use MPEG-2 video encoding (see “What Are the Video Details?” in
Chapter 3), and standard DVD players don’t recognize the MPEG-4 video