DVD Demystified

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Navigation
Because DVD-Audio-only players have no video screen, and because users
may wish to play DVD-Audio discs without turning on the television, a simplified
navigation method is specified, called simplified audio program play
(SAPP). The basic functions are play/pause, group access (jump to the first
track of a group), track access (skip to the next or previous track), index
access (skip to the next or previous index), and audio selection (choose
between audio streams). Some of these functions, such as group access and
index access, are optional. A set of still picture access commands also is
defined: next, previous, and home. Next and previous are equivalent to
“next page” and “previous page,” whereas home is equivalent to “return.”
The disc author specifies which is the home image.
Bonus Tracks
The last group on a disc can be designated for conditional access. The group
is hidden, not normally accessible to the user, unless the user knows a fourdigit
access code. Once the user enters the access code, the tracks in the last
group become playable.
The idea behind this feature is to provide bonus tracks that can be used
for prizes or incentives. There could be a series of puzzles in the disc packaging
(or even in the disc menus) that have to be solved to reveal the access
code. Or customers may need to visit a band or record label Web site to get
the code. Of course, any secret such as this will not remain a secret for long,
especially in the age of the Internet. It is inevitable that Internet sites will
post lists of all known access codes for DVD-Audio discs.
Audio Formats
Chapter 6
Linear PCM (LPCM) is mandatory on DVD-Audio discs, with up to 6 channels
at sample rates of 44.1, 48, 88.2, 96, 176.4, and 192kHz with sample
sizes of 16, 20, or 24 bits. This allows a theoretical frequency response of up
to 96 kHz and a dynamic range of up to 144 decibels. Multichannel PCM
tracks are downmixable by the player, although at 192 and 176.4 kHz, only
two channels are available. The maximum data rate for a PCM stream is
9.6 Mbps.