4. PGC categories
Following are excerpts from the Unofficial
DVD specifications Guide 2.2
...Each program chain (PGC) contains information and
commands on how to play back a
list of cells. However, PGCs are not created equal. Depending upon where it resides
on the DVD disc, there are restrictions imposed upon its commands and requirements
that the PGC has to respond to certain playback functions invoked through the user
remote control. The following illustration shows different categories of PGCs.
In general, a PGC falls into one of the following ten categories. Details of these
categories are explained in the Unofficial DVD specifications
...In the above illustration, the icon of
a user remote control key when placed next to
a PGC icon indicates that the PGC is played back when the user presses the
corresponding key on his remote control unit. The arrows in magenta indicate the
flow of virtual commands at the precommand or postcommand section of a PGC.
The numbers (1 through 6) in magenta indicate typical virtual commands used to
direct the flow and branching of playback. The domains are highlighted to show the
placement of a particular category of PGCs which are allowed by the DVD
4.1. Common virtual commands
is used to direct playback to a specified title
in a VTS. JumpTT is commonly issued from a PGC in the VMG domain or from the
is used to link from one PGC to another in
the same domain. The domain can be the VMG, VTS, or VTSM domain.
is used to direct playback from a PGC in the
title domain to a predefined menu in the same VTS, or to a PGC in the VMG domain,
or to the First-Play PGC.
is used to direct playback to a title in
the same VTS. This is the same as linking to the entry-PGC of the title.