Editing button commands

The highlight section has 5 pages:

Button commands are stored in the highlight, but defined in the associated PGC definition. This may seem odd at first, but consider that the segment containing highlights is reusable. This means there can be as many as 199 uses of the segment (two in each of 99 titlesets and one more in VMGM), each capable, because of seperate multiplexes for each domain, of having different commands. Also many of the commands available for buttons need the context of a PGC to locate cell or program names. So the PGC not only provides the context, but additionally already has statements to reference the scene within the segment. If more than one PGC defines commands for a highlight (called a menu definition) all commands must assemble to the same numerical values.

To edit button commands you must be in track mode

And enable "Show: Buttons"

Plus select a PGC. If a button is selected the "edit" button will enable and the command for the button will display to the left.

To change the current command click on the "edit" button

The VM editor will open up and display the current command and all its options

For buttons the most common command is the "LinkTailPGC". This command causes the post commands of the PGC to execute. Which button was pressed can be determined by examaning SPRM 8.
To enter this command select "Jump by Sub-Instruction", this is the class of all "Link" commands.

Now as the destination of the jump select "Post commands of current PGC"

When finished with selecting the command click "Set"

Then click "Close" to continue editing the highlight layer.

Command usage for BOV

Menus usually have one PGC per menu so determining in which menu the button was pushed is not a problem. BOV however can have the same button (usually button 1) used throughout the movie. Determining at what point in the movie the button was pressed can sometimes be determined using SPRMs, but it is usually easier to pass this information to the post commands by setting a value into a GPRM to indicate which BOV.
Start with the "Set GPRM" command.

You will need to determine which GPRM to use for this purpose, here we use GPRM 7 as an example. Select the correct GPRM, click the "immediate" radio button, and set a value for this instance of the BOV.
Now click "Link" to add the "LinkTailPGC" command as above.

Select "Jump by Sub-Instruction" and the destination is "Post commands of current PGC". Click "Set" and "close"

You may also wish to prevent the button from accidentally working when normal subpictures are displayed. To do this you need to dedicate another GPRM to BOV, its purpose is to indicate whether or not BOV is active as explained in this page. For our example we use GPRM 0.
Start with a type 3 command

Select "Compare & Set-LinkSins", the middle choice. This order of execution performs the compare first, and if it evaluates to TRUE performs the Set and then the Link, otherwise the command does nothing.

Setup the Compare and Set sections the same as the "Set GPRM" command above.
Finally set the destination of the link to "Post commands of current PGC", click "Set" and "Close"

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