|Newer page:||version 23||Last edited on Sunday, January 10, 2010 10:40:21 am||by LawrenceDoliveiro|
|Older page:||version 22||Last edited on Saturday, January 9, 2010 9:46:43 pm||by LawrenceDoliveiro||Revert|
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Each button definition in the PCI packet also lists the adjacent buttons (if any) in each of the up, down, left and right directions. This is used to switch the button selection when the user presses the corresponding key on the remote.
A button can be defined as an ''auto-action'' button. That is, the button function is invoked as soon as it is selected by the user, without having to press the "OK" key on the remote. This is used, for example, for "next page" and "previous page" options to implement multi-page menus.
[dvdauthor] doesn't bother defining any visible on-screen bounds or subpicture graphics for auto-action buttons. Presumably this is because any highlighting of such regions would never remain on-screen to be visible to the user for any length of time. However, the menu background can still provide on-screen graphics in the appropriate places (e.g. right-pointing-arrow/left-pointing-arrow for next-page/previous-page) that the user can interpret as indicating the presence of such buttons.
!More on Audio
DVD-Video is based on [MPEG]-2 files, and can use MPEG (specifically, MPEG Audio Layer 2) for its audio format. But it also allows for other audio formats: [Dolby AC-3|http://www.mpucoder.com/DVD/ac3hdr.html], [DTS|http://www.mpucoder.com/DVD/dtshdr.html] and uncompressed linear PCM (LPCM).
Instead of defining extensions to the MPEG audio stream format to cater for these options, DVD-Video puts these in an [additional private stream|http://www.mpucoder.com/DVD/ass-hdr.html] in the MPEG file.