Chapter 1

40 Everything You Ever Wanted to Know About DVD
side, with the CD player being required to read through the semitransparent
DVD layer, causing problems with some CD players
used by SACO.
• It’s a 0.6-millimeter CD substrate, with a special refractive coating
that causes a 1.2-millimeter focal depth, bonded to the back of a
0.6-millimeter DVD substrate. One side can be read by CD players,
the other side by DVD players.
• It’s a disc with two layers or two sections, one containing pressed
(DVD-ROM) data and one containing rewritable (DVD-RAM and so on)
media for recording and rerecording (more accurately called a DVD-
PROM, mixed-media, or rewritable sandwich disc.).
• It’s a disc with two layers on one side and one layer on the other (more
accurately called a DVD-14).
• It’s a disc with an embedded memory chip for storing custom usage
data and access codes (more accurately called a chipped DVD).
What’s the Deal with DTS and DVD?
DTS Digital Surround is an audio encoding format similar to Dolby Digital. It
requires a decoder, either in the player or in an external receiver (see Chapter
3’s “Audio Details of DVD-Video” for technical details). Some people
claim that, because of its lower compression level, DTS sounds better than
Dolby Digital. Others claim no perceptible difference can be discerned,
especially at the typical data rate of 768 Kbps, which is 60 percent more
than Dolby Digital. Because of the many variances in production, mixing,
decoding, and reference levels, it’s almost impossible to accurately compare
the two formats (DTS usually produces a higher volume level, causing
it to sound better in casual comparisons).
DTS originally did all encoding in house, but as of October 1999 DTS
encoders became available for purchase. DTS titles are generally considered
to be specialty items intended for audio enthusiasts. So some DTS
titles are also available in a Dolby Digital-only version.
DTS is an optional format on DVD. Contrary to uninformed claims, the
DVD specification has included an ID code for DTS since 1996 (before the
spec was even finalized). Because DTS was slow in releasing encoders and
test discs, players made before mid-1998 (and many since) ignore DTS
tracks. A few demo discs were created in 1997 by embedding DTS data into
a PCM track (the same technique used with CDs and laserdiscs), and these
are the only DTS DVD discs that work on all players. New DTS-compatible
players arrived in mid-1998, but theatrical DTS discs using the proper DTS
audio stream ID did not appear until January 7, 1999 (they were originally