Commentary

Commentary

Posted Jan 4, 2008 8:14 UTC (Fri) by ldo (subscriber, #40946)
Parent article: A dvdauthor input file

From the user viewpoint, there are two menus: the initial one in the VMGM linking to 5 titles and a "more" button, and the one in titleset 4 that is linked from that "more" button, that in turn links to the rest of the titles. Note that the "menus" sections in titlesets 2 and 3 don't contain any "video" or "vob" tags--thus, they do not define any user-visible menus, they are just places to put code sequences to be executed on entry to those titlesets.

The actual titles are spread across three titlesets (the first three)--I'm not sure why.

Note all the setting of variables g2 and g3 in the jumping back and forth--titlesets cannot jump to each other, only to menus and titles within the same titleset, and to the VMGM. In particular, see how the menus in titleset 3 have to link to their titles indirectly, via the VMGM.

The variable g4 is used to remember which button was last selected. Note the assignments between this and the variable "button", which is a synonym for the system parameter register that tells the DVD player which button is currently selected. Yes, its value has to be a multiple of 1024--that's what the DVD spec says.

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