The DVD specifications provide a set of machine instructions which tell the DVD
player how to play back the video and audio contents of the DVD. The complete set
of instructions is also known as the Virtual Machine (VM) DVD command set.
To have absolute control over your DVD authoring project without any compromise,
you will need to understand what these instructions can do. The informational guides
and real-world examples presented in this site will help you become a proficient
DVD author at the VM command level.
The VM command set is designed to direct the flow of playback and the majority of
its instructions are navigation commands. These commands can be placed at the
beginning of the PGC
(pre-commands), at the end of the
(post-commands), at the end of a cell
(cell commands), or in the navigation pack of a menu
button (button commands). Navigation commands direct playback or alter the order
of playback to jump from one video title to another. With navigation commands,
the DVD author has complete control and can design custom levels of navigation and
interactivity to instruct the DVD player to change and adapt the playback flow
The VM command set provides 16 general parameter registers
to hold temporary values and 24 system parameters
to hold information specific to the DVD player model such as region,
default language settings, parental level, etc.
Some typical usage of navigation commands:
Automatic repetition of playback of a movie title.
Change playback sequence of audio and video titles depending upon the
Select the appropriate video contents and audio language based upon the
settings users set into their DVD players.
Interactive video quizz and games.
Select fixed branching (the playback flow is not changed).
Select conditional branching (the playback flow changes depending upon
the system parameter values or user input settings).
The DVD specification has certain restrictions on playback path.
From VMG domain to a VTS domain via a title or a VTS menu.
From a title to a chapter (through an entry PGC in the VMG)
From a VTS menu or a PGC in VTSM domain to a chapter.
Playback cannot flow directly from one VTS to another but must be routed
through an entry PGC in the VMG.