Differences between version 20 and predecessor to the previous major change of DVDVideo.
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| Newer page: | version 20 | Last edited on Thursday, May 3, 2007 8:21:58 pm | by LawrenceDoliveiro | Revert |
| Older page: | version 18 | Last edited on Tuesday, May 1, 2007 9:56:24 pm | by LawrenceDoliveiro | Revert |
@@ -20,17 +20,19 @@
!Menus & Titles
Each titleset can have its own set of menus. The files comprising a titleset are named VTS_''nn''_''m''.IFO/BUP/VOB, where ''nn'' is the titleset number and ''m'' is incremented if the .VOB file needs to be broken up into multiple pieces because each file is not allowed to exceed 1GiB in size.
-There is also another titleset-like grouping called the "Video Manager" (VMGM
), of which there can only be one on the disc. This is kept in the files VIDEO_TS.IFO/BUP/VOB. This is only allowed to contain menus, no titles. It is intended to act as a top-level set of menus for accessing the various titles, though how things are actually linked together is very much up to the people authoring the DVD. There are several ways to achieve the same effect, except that one titleset cannot jump to another, only to menus and titles within the same titleset or in the VMGM
.
+There is also another titleset-like grouping called the "Video Manager" (VMG
), of which there can only be one on the disc. This is kept in the files VIDEO_TS.IFO/BUP/VOB. This is only allowed to contain menus, no titles. It is intended to act as a top-level set of menus for accessing the various titles, though how things are actually linked together is very much up to the people authoring the DVD. There are several ways to achieve the same effect, except that one titleset cannot jump to another, only to menus and titles within the same titleset or in the VMG
.
!Commands
There is a standard, very simple VirtualMachine language understood by all DVD-Video players. This is used to implement menus and buttons (using "jump" and "call" commands to link between menus and titles), but is also capable of some more complicated effects. It does not support addressing arbitrary memory or any arithmetic beyond basic 16-bit integers; however, there is a set of 16 general-purpose parameter (GPRM) registers that may be used for any purpose, plus a set of 24 System Parameter (SPRM) registers, predefined to hold such settings as the number of the currently-selected menu button, or the currently-selected audio and subtitle tracks.
!Aspect Ratios
DVD-Video caters to a maximum frame resolution of 720*576 (PAL) or 720*480 (NTSC). Certain smaller fractions of these numbers are also allowed for lower-resolution discs. The target screen aspect ratio can be either 4:3 (conventional TVs and older cinema screens) or 16:9 (newer "widescreen" TVs).
You'll notice that the pixel numbers don't match either of these ratios: 720:576 is 5:4, and 720:480 is 3:2. That's because DVD-Video has ''non-square pixels''--the horizontal and vertical pixel densities are not equal. Not only that, but 16:9 widescreen titles do not have any more horizontal pixels than 4:3 ones: instead, the pixels are simply stretched out to the wider screen.
+
+[DVDVideoTerminology] covers some more esoteric details.
Here endeth the good parts. The evil parts are described in [DVDVideoEvils].
!!See Also
