4.4. Title Menu
Following are excerpts from the Unofficial DVD specifications Guide 2.2 ebook.

...Each DVD can have one title menu for each language unit defined in the Video Manager (VMG) domain. The title menu is displayed when the "Title" button on the remote control is pressed. The title menu is used as a top-level menu through which the user can access root menus from other video title sets (VTS) on the disc, submenus in the VMG, and video titles available in video title sets.

The following illustration shows a Video Manager domain with 3 language units: English, French, and Unspecified. Depending upon the contents of the first system parameter register (SPRM0), if the default language code is English, the title menu in the English language unit is played back. The virtual command to direct playback to a title menu is JumpSS:Title Menu (hex code 3006 0000 0042 0000). Note that the selection of language unit is implied by the system parameter register SPRM0.

...Since a title menu PGC has all other properties of a standard PGC, its precommand section can be programmed to change its traditional behavior. A lot of movie DVDs have only one video title set. It is desirable in this case to have the title menu to be the same as the root menu of the video title set. In other words, pressing the "Title" button or the "Menu" button on the remote control should yield the same result. This can be achieved by providing an empty title menu PGC with a single virtual command in the precommand section to link to the root menu of a VTS. (see JumpSS VTS:Root Menu)...

For absolute control of the display of title menu in multiple languages without having to rely on the language code of SPRM0...Details on how this is accomplished are explained in the Unofficial DVD specifications Guide 2.2 ...