The menu item "Set up" displays the third menu page of the VTS when it is selected. The DVD virtual commands are used to accomplish the linkage. Before we go into the implementation details of this menu button, here is a brief explanation of how virtual commands work and how they are deployed in this project.

Each movie item in DVD-Lab Pro is a DVD data structure called Program Chain (PGC). A PGC is used to store information regarding the video and audio contents of the movie item. Before a PGC is displayed, its pre-command section is executed. After the playback of the PGC is completed, its post-command section is executed. DVD-Lab Pro allows the author to define custom virtual commands for both the pre- and post-command section. A plus sign (+) symbol is placed before and after the movie icon to indicate that there are pre-commands or post-commands present in the movie PGC.

There are 16 general storage areas available to virtual commands known as GPRM (General Parameter Registers). These registers are numbered from 0 to 15. It is a good idea to use the registers with smaller numbers since DVD-Lab Pro uses registers with larger numbers. We can set the contents of these registers to any value between 0 and 65535. Once a value is stored in any of these registers, its contents will not change when linking from one movie (PGC) to another. This feature can be used to control the branching to any movie clips or menu items in the video title set.

In this project, we are going to use two GPRMs (GPRM1 and GPRM2) to control the branching. GPRM1 is set to 0 or 1, respectively, to indicate whether the playback is continuous indefinitely, or an appropriate VTS menu at the end of each title having three contiguous movie clips. GPRM1 is set to 0 or 1 by the button commands of the menu buttons "Continuous" and "Return to menu" on the menu page "3-Setup".

The contents of GPRM2 can be 0, 1, or 2 to indicate which menu page of the VTS to display: 1-Root, 2-Chapters, or 3-Setup, respectively. The pre-command sections of the first three movie clips (1-1, 1-2, and 1-3) sets GPRM2 to 0 so that the menu page 1-Root is displayed after the end of the third movie (only if GPRM1 is 1). The pre-command sections of the last three movie clips (2-1, 2-2, and 2-3) set GPRM2 to 1 so that the menu page 2-Chapters is displayed after the end of the last movie (only if GPRM1 is 1).

GPRM2 is set to 2 by the menu button "Set up" as shown below so that when this button is selected, the menu page "3-Setup" is displayed. To define our own virtual machine (VM) command for this button, select the menu item "VM Command..." as following.

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